Policy & Integration Group

1. Little, C. M., Michael Oppenheimer, and Nathan M. Urban, March 2013: Upper bounds on twenty-first-century Antarctic ice loss assessed using a probabilistic framework. Nature Climate Change, Macmillan Publishers Limited, doi:10.1038/NCLIMATE1845
   [ Abstract ]

   Climate adaptation and flood risk assessments have incorporated sea-level rise (SLR) projections developed using semi-empirical methods (SEMs) and expert-informed mass-balance scenarios. These techniques, which do not explicitly model ice dynamics, generate upper bounds on twenty-first century SLR that are up to three times higher than Intergovernmental Panel on Climate Change estimates. However, the physical basis underlying these projections, and their likelihood of occurrence, remain unclear. Here, we develop mass-balance projections for the Antarctic ice sheet within a Bayesian probabilistic framework, integrating numerical model output and updating projections with an observational synthesis.Without abrupt, sustained, changes in ice discharge (collapse), we project a 95th percentile mass loss equivalent to ~13 cm SLR by 2100, lower than previous upper-bound projections. Substantially higher mass loss requires regional collapse, invoking dynamics that are likely to be inconsistent with the underlying assumptions of SEMs. In this probabilistic framework, the pronounced sensitivity of upper-bound SLR projections to the poorly known likelihood of collapse is lessened with constraints on the persistence and magnitude of subsequent discharge. More realistic, fully probabilistic, estimates of the ice-sheet contribution to SLR may thus be obtained by assimilating additional observations and numerical models.

2. Glaser, Alexander, and R. J. Goldston, 2012: Proliferation risks of magnetic fusion energy: clandestine production, covert production and breakout. Nuclear Fusion, IOP Publishing and International Atomic Energy Agency, 52(043004), doi:10.1088/0029-5515/52/4/043004
   [ Abstract ]

   Nuclear proliferation risks from magnetic fusion energy associated with access to weapon-usable materials can be divided into three main categories: (1) clandestine production of weapon-usable material in an undeclared facility, (2) covert production of such material in a declared facility and (3) use of a declared facility in a breakout scenario, in which a state begins production of fissile material without concealing the effort. In this paper, we address each of these categories of risks from fusion. For each case, we find that the proliferation risk from fusion systems can be much lower than the equivalent risk from fission systems, if the fusion system is designed to accommodate appropriate safeguards.

3. Little, C. M., Daniel Goldberg, A. Gnanadesikan, and Michael Oppenheimer, 2012: On the coupled response to ice-shelf basal melting. Journal of Glaciology, 58(208), doi:10.3189/2012JoG11J037 203-215
   [ Abstract ]

   Ice-shelf basal melting is tightly coupled to ice-shelf morphology. Ice shelves, in turn, are coupled to grounded ice via their influence on compressive stress at the grounding line ('ice-shelf buttressing'). Here, we examine this interaction using a local parameterization that relates the basal melt rate to the ice-shelf thickness gradient. This formulation permits a closed-form solution for a steady-state ice tongue. Time-dependent numerical simulations reveal the spatial and temporal evolution of ice-shelf/ice-stream systems in response to changes in ocean temperature, and the influence of morphology-dependent melting on grounding-line retreat.We find that a rapid (<1 year) re-equilibration in upstream regions of ice shelves establishes a spatial pattern of basal melt rates (relative to the grounding line) that persists over centuries. Coupling melting to ice-shelf shape generally, but not always, increases grounding-line retreat rates relative to a uniform distribution with the same areaaverage melt rate. Because upstream ice-shelf thickness gradients and retreat rates increase nonlinearly with thermal forcing, morphology-dependent melting is more important to the response of weakly buttressed, strongly forced ice streams grounded on beds that slope upwards towards the ocean (e.g. those in the Amundsen Sea).

4. Tavoni, M., Shoibal Chakravarty, and Robert H. Socolow, 2012: Safe vs. Fair: A Formidable Trade-off in Tackling Climate Change. Sustainability, Basel, Switzerland, MDPI Publishing, 4(2), doi:10.3390/su4020210 210-226
   [ Abstract ]

   Global warming requires a response characterized by forward-looking management of atmospheric carbon and respect for ethical principles. Both safety and fairness must be pursued, and there are severe trade-offs as these are intertwined by the limited headroom for additional atmospheric CO₂ emissions. This paper provides a simple numerical mapping at the aggregated level of developed vs. developing countries in which safety and fairness are formulated in terms of cumulative emissions and cumulative per capita emissions respectively. It becomes evident that safety and fairness cannot be achieved simultaneously for strict definitions of both. The paper further posits potential global trading in future cumulative emissions budgets in a world where financial transactions compensate for physical emissions: the safe vs. fair tradeoff is less severe but remains formidable. Finally, we explore very large deployment of engineered carbon sinks and show that roughly 1,000 Gt CO₂ of cumulative negative emissions over the century are required to have a significant effect, a remarkable scale of deployment. We also identify the unexplored issue of how such sinks might be treated in sub-global carbon accounting.

5. Al-Housseiny, Talal, Peichun Tsai, Zhong Zheng, and Howard Stone, 2011: The effect of permeability gradients on immiscible displacement in Hele-Shaw flows. American Physical Society,
   [ Abstract ]

   In heterogeneous media, it is well known that when a fluid of high viscosity displaces a less viscous fluid, the interface can still be unstable and exhibit finger-like patterns due to capillary fingering. Motivated by porous media flows in natural geological formations, we consider homogeneous displacement in a Hele-Shaw cell subjected to a permeability gradient. The permeability gradient is introduced by linearly varying the Hele-Shaw cell depth. We study how capillary forces can affect interfacial stability in the presence of the gradient via linear stability analysis. Depending on the system, we find that surface tension can either have a stabilizing or a destabilizing role. We report the emergence of an important dimensionless parameter--the ratio of the permeability gradient to the capillary number--that determines the stability of the interface along with the well-studied viscosity ratio. Experiments testing the theoretical findings will also be presented.

6. Liu, Guangjian, Eric Larson, Robert H. Williams, Thomas Kreutz, and Xiangbo Guo, 2011: Making Fischer-Tropsch Fuels and Electricity from Coal and Biomass: Performance and Cost Analysis. Energy Fuels, Published on Web 12/06/2010, (25), doi:10.1021/ef101184e 415-437
   [ Abstract ]

   Major challenges posed by crude-oil-derived transportation fuels are high current and prospective oil prices, insecurity of liquid fuel supplies, and climate change risks from the accumulation of fossil fuel CO₂ and other greenhouse gases in the atmosphere. One option for addressing these challenges simultaneously involves producing ultraclean synthetic fuels from coal and lignocellulosic biomass with CO₂ capture and storage. Detailed process simulations, lifecycle greenhouse gas emissions analyses, and cost analyses carried out in a comprehensive analytical framework are presented for 16 alternative system configurations that involve gasification-based coproduction of Fischer-Tropsch liquid (FTL) fuels and electricity from coal and/or biomass, with and without capture and storage of byproduct CO₂. Systematic comparisons are made to cellulosic ethanol as an alternative low GHG-emitting liquid fuel and to alternative options for decarbonizing stand-alone fossil-fuel power plants. The analysis indicates that FTL fuels are typically less costly to produce when electricity is generated as a major coproduct than when producing mainly liquid fuel. Coproduction systems that utilize a cofeed of biomass and coal and incorporate CO₂ capture and storage in the design offer attractive opportunities for decarbonizing liquid fuels and power generation simultaneously. Such coproduction systems considered as power generators can provide decarbonized electricity at lower costs than is feasible with stand-alone fossil-fuel power plant options under a wide range of conditions. At a plausible GHG emissions price under a future U.S. carbon mitigation policy ($50/t CO_2eq), such a coproduction system built at a scale suitable for competing as a power generator would be able to provide low-GHG-emitting synthetic fuels at the same estimated unit cost as for coal synfuels characterized by ten times the GHG gas emission rate that are produced in a plant with CO₂ capture and storage that does not provide electricity as a major coproduct having three times the synfuel output capacity and requiring twice the total capital investment. Moreover, the low GHG-emitting synfuels produced by such systems would be less costly to produce than cellulosic ethanol and require only half as much lignocellulosic biomass.

7. O'Reilly, Jessica, Keynyn Brysse, Michael Oppenheimer, and Naomi Oreskes, 2011: Characterizing uncertainty in expert assessments: ozone depletion and the West Antarctic ice sheet. WIREs Climate Change, John Wiley & Sons, Ltd., doi:10.1002/wcc.135
   [ Abstract ]

   Large-scale assessments have become an important vehicle for organizing, interpreting, and presenting scientific information relevant to environmental policy. At the same time, identifying and evaluating scientific uncertainty with respect to the very questions these assessments were designed to address has become more difficult, as ever more complex problems involving greater portions of the Earth system and longer timescales have emerged at the science-policy interface. In this article, we explore expert judgments about uncertainty in two recent cases: the assessment of stratospheric ozone depletion, and the assessment of the response of the West Antarctic ice sheet (WAIS) to global warming. These assessments were fairly adept at characterizing one type of uncertainty in models (parameter uncertainty), but faced much greater difficulty in dealing with structural model uncertainty, sometimes entirely avoiding grappling with it. In the absence of viable models, innovative approaches were developed in the ozone case for consolidating information about highly uncertain future outcomes, whereas little such progress has been made thus far in the case of WAIS. Both cases illustrate the problem of expert disagreement, suggesting that future assessments need to develop improved approaches to representing internal conflicts of judgment, in order to produce amore complete evaluation of uncertainty.

8. Palter, J. B., M. Susan Lozier, Jorge Sarmiento, and Robert H. Williams, 2011: The supply of excess phosphate across the Gulf Stream and the maintenance of subtropical nitrogen fixation. Global Biogeochemical Cycles, American Geophysical Union, 25(GB4007), doi:10.1029/2010GB003955
   [ Abstract ]

   The subtropical North Atlantic is considered a hot spot for biological nitrogen fixation, with estimated rates between 1 and 20 x 10¹¹ mol nitrogen fixed annually. However, the region's nutrient reservoir beneath the euphotic zone is so enriched in nitrate relative to phosphate that it is perplexing how fixation might be sustained there. Here, we investigate whether the physical transport of excess phosphate into the subtropical gyre is sufficient to sustain nitrogen fixation in the gyre. Specifically, we assess the Ekman advection and isopycnal mixing of excess phosphate to the subtropical North Atlantic, using detailed hydrographic and nutrient sections occupied across the Gulf Stream combined with satellite wind data. Ekman advection and along-isopycnal mixing provide a source of approximately 2 x 10¹⁰ mol yr of excess phosphate in the northwestern subtropics, a physical mechanism that has the potential to support more than 3 x 10¹¹ mol yr^-1 of biological nitrogen fixation, after accounting for alternative sinks of excess phosphate. This excess phosphate supply across the gyre's northern boundary and high nitrogen fixation there offers a mechanism that can explain both the maintenance of subtropical North Atlantic nitrogen fixation in a phosphate-poor environment and help account for the weak gradients in the proxies of fixation observed along interior circulation pathways of the gyre.

9. Socolow, Robert H., and Mary R. English, 2011: Living ethically in a greenhouse In The Ethics of Global Climate Change, Edited by Denis G. Arnold, Cambridge University Press, doi:10.1017/CBO9780511732294.009 170-191
   [ Abstract ]

   It was made clear at the December 2009 conference on climate change in Copenhagen (Conference of the Parties 15) that the nations of the world are only beginning to concede that they face a common threat. It was widely reported that there was a deep divide at Copenhagen between delegates from "developed" countries and delegates from "developing" countries, and that the depth of the anger of the delegates from developing countries surprised the delegates from developed countries. Should the anger have been surprising? Not only had some of the developed countries - most notably, the USA - failed to take significant steps prior to the meeting to reduce the impacts of their economies on the climate. In addition, the developed countries had come to the meeting to revise the global structure of climate change mitigation such that all countries (or at least all of the major economies) would share the task. This arrangement, all conceded, entailed a sharp departure from the previous structure, in place since the 1992 United Nations Framework Convention on Climate Change, which dealt with equity across nations by dividing the world into two groups of countries with "common but differentiated responsibilities." Only the group of "Annex 1" countries (approximately, the countries of the Organization for Economic Cooperation and Development plus Russia) was obligated to make legally binding mitigation commitments.

10. Socolow, Robert H., et al., 2011: America's Climate Choices, Committee on America's Climate Choices. National Research Council, The National Academies Press: 144pp.
    [ Abstract ]

    Climate change is occurring, is very likely caused primarily by the emission of greenhouse gases from human activities, and poses significant risks for a range of human and natural systems. Emissions continue to increase, which will result in further change and greater risks. In the judgment of this report's authoring committee, the environmental, economic, and humanitarian risks posed by climate change indicate a pressing need for substantial action to limit the magnitude of climate change and to prepare for adapting to its impacts.

11. Socolow, Robert H., et al., 2011: Direct Air Capture of CO₂ with Chemicals, A Technology Assessment for the APS Panel on Public Affairs. American Physical Society, http://www.aps.org/policy/reports/assessments/index.cfm, (June 1, 2011), 94pp.
    [ Abstract ]

    This report explores direct air capture (DAC) of carbon dioxide (CO₂) from the atmosphere with chemicals. DAC involves a system in which ambient air flows over a chemical sorbent that selectively removes the CO₂. The CO₂ is then released as a concentrated stream for disposal or reuse, while the sorbent is regenerated and the CO₂-depleted air is returned to the atmosphere.

12. Socolow, Robert H., 2011: High-consequence outcomes and internal disagreements: tell us more, please. Climatic Change, Springer, doi:10.1007/s10584-011-0187-5
    [ Abstract ]

    This article is one of several in this special double-issue that reports the views of "users" of IPCC reports. I am a user in the sense that I advise the policy-making community and rely on the IPCC reports to provide me with authoritative views on the state of the science. My principal recommendation for making the IPCC more helpful to the policy-making community is to strive in the Fifth Assessment Report (AR5) to communicate fully what the climate science community understands and does not understand about high-consequence outcomes. This will require the AR5 authors to provide vivid information about future worlds where high-consequence outcomes have emerged. It will also require the AR5 authors to reveal any disagreements persisting among them after the give-and-take of the writing process has run its course. In the Fourth Assessment Report (AR4) the presentation of high-consequence outcomes had shortcomings that can be rectified in AR5.

13. Socolow, Robert H., September 2011: Wedges Reaffirmed. Bulletin of the Atomic Scientists, www.thebulletin.org,
    [ Abstract ]

    In August 2004 Steve Pacala and I published a paper in Science about climate change mitigation. Its core messages are as valid today as seven years ago, but they have not led to action. Here, I suggest that public resistance can be partially explained by shortcomings in the way advocates of forceful action have presented their case. Addressing these shortcomings might put the world back on the course we identified.

14. Williams, Robert H., Guangjian Liu, Thomas Kreutz, and Eric Larson, 2011: Coal and Biomass to Fuels and Power. Annual Review of Chemical and Biomolecular Engineering, 2, doi:10.1146/annurev-chembioeng-061010-114126 529-553
    [ Abstract ]

    Systems with CO₂ capture and storage (CCS) that coproduce transportation fuels and electricity from coal plus biomass can address simultaneously challenges of climate change from fossil energy and dependence on imported oil. Under a strong carbon policy, such systems can provide competitively clean low-carbon energy from secure domestic feedstocks by exploiting the negative emissions benefit of underground storage of biomass-derived CO₂, the low cost of coal, the scale economies of coal energy conversion, the inherently low cost of CO₂ capture, the thermodynamic advantages of coproduction, and expected high oil prices. Such systems requiremuch less biomass to make low-carbon fuels than do biofuels processes. The economics are especially attractive when these coproduction systems are deployed as alternatives to CCS for stand-alone fossil fuel power plants. If CCS proves to be viable as a major carbon mitigation option, the main obstacles to deployment of coproduction systems as power generators would be institutional.

15. Gnanadesikan, A., K. A. Emanuel, Gabriel A. Vecchi, Whit G. Anderson, and R. Hallberg, July 2010: How Ocean color can steer Pacific tropical cyclones. Geophysical Research Letters, (InPress),
    [ Abstract ]

    Because ocean color alters the absorption of sunlight, it can produce changes in sea surface temperatures with further impacts on atmospheric circulation. These changes can project onto fields previously recognized to alter the distribution of tropical cyclones. If the North Pacific subtropical gyre contained no absorbing and scattering materials, the result would be to reduce subtropical cyclone activity in the subtropical Northwest Pacific by 2/3, while concentrating cyclone tracks along the equator. Predicting tropical cyclone activity using coupled models may thus require consideration of the details of how heat moves into the upper thermocline as well as biogeochemical cycling.

16. Larson, Eric, G. Fiorese, Guangjian Liu, and Robert H. Williams, et al., 2010: Co-production of decarbonized synfuels and electricity from coal + biomass. Energy and Environmental Science, 3, doi:10.1039/b911529c 28-42
    [ Abstract ]

    Energy, carbon, and economic performances are estimated for facilities co-producing Fischer–Tropsch Liquid (FTL) fuels and electricity from a co-feed of biomass and coal in Illinois, with capture and storage of by-product CO₂. The estimates include detailed modeling of supply systems for corn stover or mixed prairie grasses (MPG) and of feedstock conversion facilities. Biomass feedstock costs in Illinois (delivered at a rate of one million tonnes per year, dry basis) are $ 3.8/GJ_HHV for corn stover and $ 7.2/GJ_HHV for MPG. Under a strong carbon mitigation policy, the economics of co-producing lowcarbon fuels and electricity from a co-feed of biomass and coal in Illinois are promising. An extrapolation to the United States of the results for Illinois suggests that nationally significant amounts of low-carbon fuels and electricity could be produced this way.

17. Liu, Guangjian, Robert H. Williams, Eric Larson, and Thomas Kreutz, 2010: Design Economics of Low-Carbon Power Generation from Natural Gas and Biomass with Synthetic Fuels Co-Production. International Conference on Greenhouse Gas Technologies (GHGT 10), Elsevier/Energy Procedia,
    [ Abstract ]

    There is growing optimism about the prospects for large natural gas reserves in shale formations. This paper explores the feasibility vis-à-vis coal power generation of a new approach for decarbonized natural gas power generation. Key features of process designs examined here are coproduction of synthetic transportation fuels with electricity and co-feeding of some biomass with natural gas in such co-production systems. Key questions addressed in the analysis of these systems are: 1) can the competitiveness of natural gas in economic dispatch be improved vis-à-vis a natural gas combined cycle, and 2) can the GHG emissions price needed to induce CCS for natural gas power generation be reduced from that required to induce CCS for NGCC. We find that gas/biomass co-production systems with CCS will be able to defend high capacity factors in economic dispatch at projected oil prices with only modest GHG emission prices. We also find that the breakeven GHG emission price needed to induce CCS for natural gas power generation is reduced considerably vis-à-vis NGCC-CCS.

18. Naik, V., A. M. Fiore, L. W. Horowitz, and H. B. Singh, et al., 2010: Observational constraints on the global atmospheric budget of ethanol. Atomsphere Chemistry and Physics Discussion, http://www.atmos-chem-phys-discuss.net/10/925/2010/acpd-10-925-2010.pdf, 10, 925-945
    [ Abstract ]

    Energy security and climate change concerns have led to the promotion of biomass-derived ethanol, an oxygenated volatile organic compound (OVOC), as a substitute for fossil fuels. Although ethanol is ubiquitous in the troposphere, our knowledge of its current atmospheric budget and distribution is limited. Here, for the first time we use a global chemical transport model in conjunction with atmospheric observations to place constraints on the ethanol budget, noting that additional measurements of ethanol (and its precursors) are still needed to enhance confidence in our estimated budget. Global sources of ethanol in the model include 5.0 Tg yr⁻¹from industrial sources and biofuels, 9.2 Tg yr⁻¹ from terrestrial plants, ~0.5 Tg yr⁻¹ from biomass burning, and 0.05 Tg yr⁻¹ from atmospheric reactions of the ethyl peroxide radical (C₂H₅O₂) with itself and with the methyl peroxide radical (CH₃O₂). The resulting atmospheric lifetime of ethanol in the model is 2.8 days. Gas-phase oxidation by hydroxyl radical (OH) is the primary global sink of ethanol in the model (65%), followed by dry deposition to land (25%), and wet deposition (10%). Over continental areas, ethanol concentrations predominantly reflect direct anthropogenic and biogenic emission sources. Uncertainty in the biogenic ethanol emissions estimated at a factor of three may contribute to the 50% model underestimate of observations in the North American boundary layer. Furthermore, current levels of ethanol measured in remote atmospheres are an order of magnitude larger than those explained by surface sources or by in-situ atmospheric production from observed precursor hydrocarbons in the model, suggesting a major gap in understanding. Stronger constraints on the budget and distribution of ethanol and other VOCs are a critical step towards assessing the impacts of increasing use of ethanol as a fuel.

19. Tavoni, M., and R.S.J. Tol, 2010: Counting only the hits? The risk of underestimating the costs of a stringent climate policy. Climatic Change, doi:10.1007/s10584-010-9867-9
    [ Abstract ]

    This paper warns against the risk of underestimating the costs—and the uncertainty about the costs—of achieving stringent stabilization targets. We argue that a straightforward review of integrated assessment models results produces biased estimates for the more ambitious climate objectives such as those compatible with the 2°C of the European Union and the G8. The magnitude and range of estimates are significantly reduced because only the most optimistic results are reported for such targets. We suggest a procedure that addresses this partiality. The results show highly variable costs for the most ambitious scenarios.

20. Turner, Will R., B. A. Bradley, Lyndon D. Estes, Michael Oppenheimer, and David S. Wilcove, August 2010: Climate Change: Helping Nature Survive the Human Response. Conservation International, doi:10.1111/j.1755-263X.2010.00128.x
    [ Abstract ]

    Climate change poses profound, direct, and well-documented threats to biodiversity. A significant fraction of Earth’s species is at risk of extinction due to changing precipitation and temperature regimes, rising and acidifying oceans, and other factors. There is also growing awareness of the diversity and magnitude of responses, both proactive and reactive, that people will undertake as lives and livelihoods are affected by climate change. Yet to date few studies have examined the relationship between these two powerful forces. The natural systems upon which people depend, already under direct assault from climate change, are further threatened by how we respond to climate change. Human history and recent studies suggest that our actions to cope with climate change (adaptation) or lessen its rate and magnitude (mitigation) could have impacts that match—and even exceed—the direct effects of climate change on ecosystems. If we are to successfully conserve biodiversity and maintain ecosystem services in a warming world, considerable effort is needed to predict and reduce the indirect risks created by climate change.

21. Williams, Robert H., Guangjian Liu, Thomas Kreutz, and Eric Larson, 2010: Alternatives for Decarbonizing Existing USA Coal Power Plant Sites. International Conference on Greenhouse Gas Technologies (GHGT 10), Elsevier/Energy Procedia,
    [ Abstract ]

    A CO₂ capture and storage (CCS) retrofit strategy is compared to several repowering strategies for decarbonising existing coal power plant sites. The more promising repowering approaches analyzed seem to be a shift to natural gas via natural gas combined cycles and deployment of systems that coproduce synthetic liquid fuels plus electricity from coal and biomass with CCS. Under a wide range of plausible conditions, the latter option seems to the most promising approach for decarbonising these plant sites—exploiting simultaneously the carbon mitigation benefit of coprocessing biomass in CCS energy systems and the more general benefits offered by coproduction systems with CCS of: (i) a low CO₂ capture cost, (ii) a high efficiency of power generation, and (iii) large credit for the sale of the synfuel coproducts at current or higher oil prices.

22. Xu, Y., C.T. Supuran, and Francois Morel, 2010: Cadmium-carbonic anhyrase (In Press). Handbook of Metalloproteins,
23. Zheng, Zhong, Eric Larson, Z. Li, Guangjian Liu, and Robert H. Williams, 2010: Near-term mega-scale CO₂ capture and storage demonstration opportunities in China. Energy and Environmental Science, The Royal Society of Chemistry, 3(9), doi:10.1039/B924243K 1153-1169
    [ Abstract ]

    China is unique in the large number (nearly 400) of existing and planned projects for making ammonia, methanol, and other fuels and chemicals from coal. A natural by-product of these processes is a nearly pure CO₂ stream. Collectively, these facilities will emit (once all are operating) some 270 million tonnes of CO₂ per year. Taking advantage of the relatively low cost of capturing these CO₂ streams (as compared with capturing CO₂ from power plant flue gases), some of the 20 large-scale CO₂ capture and storage (CCS) demonstration projects called for by the leaders from the G8 to be deployed during the next decade might be expeditiously located in China. Our analysis identifies 18 coal-chemicals/fuels facilities, each emitting one million tonnes/year or more of CO₂, that are within 10 km of prospective deep saline aquifer CO₂ storage sites and an additional 8 facilities within 100 km. The potential CO₂ storage basins are identified based on work by others. We adapted two published cost models for CO₂ compression and transport to develop preliminary estimates of prospective costs for potential CCS projects in China. Our "N^th plant" cost estimates for the 18 projects where the CO₂ source is within 10 km of a sink, are between $9 and $13/tonne of CO₂. (The highest cost estimate among all evaluated projects was less than $21/tonne of CO₂.) The 10-year net-present value cost for projects ranged from $89 million to $1.15 billion, with more than 75% of the projects having net present value costs of $200 million or less. These relatively modest CCS costs suggest that there would be mutual value in international cooperation to support CCS demonstrations in China.

24. Blackstock, Jason J., D. S. Battisti, K. Caldeira, D. M. Eardeley, J. I. Katz, D. W. Keith, A.A.N. Patrinos, D. P. Schrag, Robert H. Socolow, and S. E. Koonin, 2009: Climate Engineering Responses to Climate Emergencies. NOVIM Group,
    [ Abstract ]

    Despite efforts to stabilize CO₂ concentrations, it is possible that the climate system could respond abruptly with catastrophic consequences. Intentional intervention in the climate system to avoid or ameliorate such consequences has been proposed as one possible response should such a scenario arise. In a one-week study, the authors of this report conducted a technical review and evaluation of proposed climate engineering concepts that might serve as a rapid palliative response to such climate emergency scenarios.
    Because of their potential to induce a prompt (<1 yr) global cooling, this study concentrated on Shortwave Climate Engineering (SWCE) methods for moderately reducing the amount of shortwave solar radiation absorbed by the Earth. The study’s main objective was to outline a decade-long agenda of technical research that would maximally reduce the uncertainty surrounding the benefits and risks associated with SWCE. For rigor of technical analysis, the study focused the research agenda on one particular SWCE concept—stratospheric aerosol injection—and in doing so developed several conceptual frameworks and methods valuable for assessing any SWCE proposal.
    Basic physical science considerations, exploratory climate modeling, and the impacts of volcanic aerosols on climate all suggest that SWCE could partially compensate for some effects— particularly net global warming—of increased atmospheric CO₂. However, existing data also reveal important limits to the range of CO₂ impacts that SWCE could ameliorate; for example, ongoing ocean acidification would not be affected, and some categories of climate emergency scenario might prove unresponsive to SWCE. Moreover, significant uncertainty presently surrounds the spatial and temporal response of numerous climate and ecological parameters to SWCE, making the near-term deployment of large-scale SWCE extraordinarily risky.
    Components of any comprehensive research agenda for reducing these uncertainties can be divided into three progressive phases: (I) Non-Invasive Laboratory and Computational Research; (II) Field Experiments; and (III) Monitored Deployment. Each phase involves distinct and escalating risks (both technical and socio-political), while simultaneously providing data of greater value for reducing uncertainties.
    The core questions that need to be addressed can also be clustered into three streams of research: Engineering (intervention system development); Climate Science (modeling and experimentation to understand and anticipate impacts of the intervention); and Climate Monitoring (detecting and assessing the actual impacts, both anticipated and unanticipated). While a number of studies have suggested the engineering feasibility of specific SWCE proposals, the questions in the Climate Science and Climate Monitoring streams present far greater challenges due to the inherent complexity of temporal and spatial delays and feedbacks within the climate system.
    These frameworks are applied to structure the comprehensive research agenda outlined for stratospheric aerosol SWCE in Part 3 of this report. For the Engineering stream, current understanding, questions and methods guiding the necessary research into aerosol material, stratospheric lofting and dispersion are all defined. For the Climate Science and Climate Monitoring streams, emphasis is placed on identifying, predicting and monitoring the response of important climate parameters across four broad categories: Radiative, Geophysical, Geochemical and Ecological. Finally, the components within each stream are identified as belonging to Phase I or II research, and the limits placed by the natural variability of the climate system on what can be learned from low-level Phase II field-testing are roughly assessed.
    This report does not attempt to evaluate whether stratospheric aerosol (or any other) SWCE systems should be developed or deployed—or even whether any parts of the outlined research program should be pursued. Such questions are the subject of an intense ongoing debate, involving socio-political and economic issues beyond the scope of this study. This report aims to better inform that debate by elucidating the technical research agenda that would be necessary to reduce the uncertainty in potential SWCE interventions.

25. Bosetti, V., C. Carraro, and M. Tavoni, November 2009: A Chinese Commitment to Commit: Can it Break the Negotiation Stall? Climatic Change, Netherlands, Springer, 97(No. 1-2), doi:10.1007/s10584-009-9726-8 297-303
    [ Abstract PDF ]

    Preparatory talks to the next round of negotiations seem to indicate that a comprehensive agreement to mitigate climate change will not be easily attainable, despite the intentions of the US administration and the high expectations surrounding the Copenhagen meeting. One key reason is to what extent fast growing economies, and especially China, should take actions to reduce their growth of emissions. This paper argues that a turning point for international negotiations on climate change could be achieved if China were to agree on carbon obligations in the future. Results from modelling work suggest that the optimal investment behaviour is to anticipate the implementation of a climate policy by roughly 10 years, and that thus future commitments—if credible—could lead to significantly earlier steps towards carbon mitigation. If fast growing economies, and foremost China, believe in the long term objective of global stabilization of carbon concentrations, it might be economically rationale to sign on future targets, provided developed countries take on immediate action. Such a provision could be beneficial for both the developing and developed world.

26. Bradley, B. A., Michael Oppenheimer, and David S. Wilcove, 2009: Climate Change and Plant Invasions: Restoration Opportunities Ahead. Global Change Biology, 15(6), doi:10.1111/j.1365-2486.2008.01824.x 1511-1521
    [ Abstract ]

    Rather than simply enhancing invasion risk, climate change may also reduce invasive plant competitiveness if conditions become climatically unsuitable. Using bioclimatic envelope modeling, we show that climate change could result in both range expansion and contraction for five widespread and dominant invasive plants in the western United States. Yellow starthistle (Centaurea solstitialis) and tamarisk (Tamarix spp.) are likely to expand with climate change. Cheatgrass (Bromus tectorum) and spotted knapweed (Centaurea biebersteinii) are likely to shift in range, leading to both expansion and contraction. Leafy spurge (Euphorbia esula) is likely to contract. The retreat of onceintractable invasive species could create restoration opportunities across millions of hectares. Identifying and establishing native or novel species in places where invasive species contract will pose a considerable challenge for ecologists and land managers. This challenge must be addressed before other undesirable species invade and eliminate restoration opportunities.

27. Chakravarty, Shoibal, A. Chikkatur, H. de Coninck, Stephen W. Pacala, Robert H. Socolow, and M. Tavoni, 2009: Sharing global CO₂ emission reductions among one billion high emitters. Proceedings of the National Academy of Sciences of the United States of America, 106(29), doi:10.1073/pnas.0905232106 11884-11888
    [ Abstract ]

    We present a framework for allocating a global carbon reduction target among nations, in which the concept of ‘‘common but differentiated responsibilities’’ refers to the emissions of individuals instead of nations. We use the income distribution of a country to estimate how its fossil fuel CO₂ emissions are distributed among its citizens, from which we build up a global CO₂ distribution. We then propose a simple rule to derive a universal cap on global individual emissions and find corresponding limits on national aggregate emissions from this cap. All of the world’s high CO₂ emitting individuals are treated the same, regardless of where they live. Any future global emission goal (target and time frame) can be converted into national reduction targets, which are determined by ‘‘Business as Usual’’ projections of national carbon emissions and incountry income distributions. For example, reducing projected global emissions in 2030 by 13 GtCO₂ would require the engagement of 1.13 billion high emitters, roughly equally distributed in 4 regions: the U.S., the OECD minus the U.S., China, and the nonOECD minus China. We also modify our methodology to place a floor on emissions of the world’s lowest CO₂ emitters and demonstrate that climate mitigation and alleviation of extreme poverty are largely decoupled.

28. Chakravarty, Shoibal, Robert H. Socolow, and M. Tavoni, November 2009: A Focus on Individuals Can Guide Nations Towards a Low Carbon World. Climate Science and Policy, http://www.climatescienceandpolicy.eu/2009/11/a-focus-on-individuals-can-guide-nations-towards-a-low-carbon-world/, Nov. 13, 2009,
    [ PDF ]
29. Chakravarty, Shoibal, and M. V. Ramana, November 2009: India's Evolving Climate Change Strategy. Climate Science and Policy, http://www.climatescienceandpolicy.eu/2009/11/indias-evolving-climate-change-strategy/, (Nov. 13, 2009),
    [ PDF ]
30. Chakravarty, Shoibal, A. Chikkatur, H. de Coninck, Stephen W. Pacala, M. Tavoni, and Robert H. Socolow, 2009: Reply to Grubler and Pachauri: Developing national obligations from individual emissions. Proceedings of the National Academy of Sciences of the United States of America, 106(43 E124), doi:10.1073/pnas.0911102106
31. Dryer, F. L., Robert H. Williams, and Eric Larson, August 2009: How Aviation Can Clean up its Act. BBC News, http://news.bbc.co.uk/2/hi/sci/tech/8193125.stm,
32. Gerber, S., L.O. Hedin, Michael Oppenheimer, Stephen W. Pacala, and E. Shevliakova, 2009: Nitrogen Cycling and Feedbacks in a Global Dynamic Land Model. Global Biogeochemical Cycles, http://www.agu.org/journals/pip/gb/2008GB003336-pip.pdf, doi:10.1029/2008GB003336
    [ Abstract ]

    Global anthropogenic changes in carbon (C) and nitrogen (N) cycles call for modeling tools that are able to address and quantify essential interactions between N, C, and climate in terrestrial ecosystems. Here, we introduce a prognostic N cycle within the Princeton-GFDL LM3V land model. The model captures mechanisms essential for N cycling and their feedbacks on C cycling: N limitation of plant productivity, the N dependence of C decomposition and stabilization in soils, removal of available N by competing sinks, ecosystem losses that include dissolved organic and volatile N, and ecosystem inputs through biological N fixation.
    Our model captures many essential characteristics of C-N interactions, and is capable of broadly recreating spatial and temporal variations in N and C dynamics. The introduced N dynamics improves the model’s short term NPP response to step changes in CO₂. Consistent with theories of successional dynamics, we find that physical disturbance induces strong C-N feedbacks, caused by intermittent N loss and subsequent N limitation. In contrast, C-N interactions are weak when the coupled model system approaches equilibrium. Thus, at steady state many simulated features of the carbon cycle, such as primary productivity and carbon inventories are similar to simulations that do not include C-N feedbacks.

33. Kopp, Robert E., Frederick J. Simons, Jerry X. Mitrovica, Adam C. Maloof, and Michael Oppenheimer, December 2009: Probabilistic assessment of sea level during the last interglacial stage. Nature, New York, NY, Macmillan, 462, 863-867(17 December 2009), doi:10.1038/nature08686
    [ Abstract ]

    With polar temperatures ~ 3-5° warmer than today, the last interglacial stage (~125 kyr ago) serves as a partial analogue for 1-2° global warming scenarios. Geological records from several sites indicate that local sea levels during the last interglacial were higher than today, but because local sea levels differ from global sea level, accurately reconstructing past global sea level requires an integrated analysis of globally distributed data sets. Here we present an extensive compilation of local sea level indicators and a statistical approach for estimating global sea level, local sea levels, ice sheet volumes and their associated uncertainties. We find a 95% probability that global sea level peaked at least 6.6m higher than today during the last interglacial; it is likely (67% probability) to have exceeded 8.0m but is unlikely (33% probability) to have exceeded 9.4 m. When global sea level was close to its current level (>10m), the millennial average rate of global sea level rise is very likely to have exceeded 5.6mkyr^-1 but is unlikely to have exceeded 9.2mkyr^-1. Our analysis extends previous last interglacial sea level studies by integrating literature observations within a probabilistic framework that accounts for the physics of sea level change. The results highlight the long-term vulnerability of ice sheets to even relatively low levels of sustained global warming.

34. Larson, Eric, G. Fiorese, Guangjian Liu, Robert H. Williams, Thomas Kreutz, and S. Consonni, 2009: Co-production of decarbonized synfuels and electricity from coal + biomass with CO₂ capture and storage: an Illinois case study. Energy and Environmental Science,
    [ Abstract ]

    Energy, carbon, and economic performance are estimated for facilities co-producing Fischer- Tropsch Liquid (FTL) fuels and electricity from a co-feed of biomass and coal in Illinois, with capture and storage of by-product CO₂. The estimates include detailed models of supply systems for corn stover or mixed prairie grasses (MPG) and of feedstock conversion facilities. Biomass feedstock costs in Illinois (delivered at a rate of one million tonnes per year, dry basis) are $3.8 GJ_HHV for corn stover and $7.2/GJ_HHV for MPG. Using a strong carbon mitigation policy, the economics of co-producing low-carbon fuels and electricity from a co-feed of biomass and coal in Illinois are promising. An exploration to the United States of the results for Illinois suggests that nationally significant amounts of low-carbon fuels and electricity could be produced this way.

35. Searchinger, Timothy, Steven P. Hamburg, J. M. Melillo, W. Chameides, Petr Havlik, Daniel M. Kammen, Gene E. Likens, Ruben N. Lubowski, M. Obersteiner, Michael Oppenheimer, G. Philip Robertson, William H. Schlesinger, and G. David Tilman, October 2009: Fixing a Critical Climate Accounting Error. Science, Washington, D.C., American Association for the Advancement of Science, 326(5952), doi:10.1126/science.1178797 527-528
    [ Abstract ]

    The accounting now used for assessing compliance with carbon limits in the Kyoto Protocol and in climate legislation contains a far-reaching but fixable flaw that will severely undermine greenhouse gas reduction goals (1). It does not count CO₂ emitted from tailpipes and smokestacks when bioenergy is being used, but it also does not count changes in emissions from land use when biomass for energy is harvested or grown. This accounting erroneously treats all bioenergy as carbon neutral regardless of the source of the biomass, which may cause large differences in net emissions. For example, the clearing of long-established forests to burn wood or to grow energy crops is counted as a 100% reduction in energy emissions despite causing large releases of carbon.

36. Shapiro, H. T., M. S. Wrighton, J. F. Ahearne, A. J. Bard, J. Beyea, William F. Brinkman, D. M. Chapin, S. Chu, C. A. Ehlig-Economides, R. W. Fri, C. H. Goodman, J. B. Heywood, L. B. Lave, J. J. Markowsky, R. A. Meserve, W. F. Miller Jr., F. M. Orr, Jr., L. T. Papay, A.A.N. Patrinos, M. P. Ramage, M. L. Savitz, Robert H. Socolow, J. L. Sweeney, G. D. Tilman, and C. Walton, 2009: America's Energy Future: Technology and Transformation. Committee on America's Energy Future, National Research Council of the National Academies,, Washington, D.C., The National Academies Press, (ISBN-10: 0-309-14141),
    [ Abstract ]

    To stimulate and inform a constructive national dialogue about our energy future, the National Academy of Sciences and the National Academy of Engineering initiated in 2007 a major study, "America's Energy Future: Technology Opportunities, Risks, and Tradeoffs." The America's Energy Future (AEF) project was initiated in anticipation of major legislative interest in energy policy in the U.S. Congress and, as the effort proceeded, it was endorsed by Senate Energy and Natural Resources Committee Chair Jeff Bingaman and former Ranking Member Pete Domenici.
    The AEF project evaluates current contributions and the likely future impacts, including estimated costs, of existing and new energy technologies. It was planned to serve as a foundation for subsequent policy studies, at the Academies and elsewhere, that will focus on energy research and development priorities, strategic energy technology development, and policy analysis.
    The AEF project has produced a series of five reports, including this report, designed to inform key decisions as the nation begins this year a comprehensive examination of energy policy issues. Numerous studies conducted by diverse organizations have benefited the project, but many of those studies disagree about the potential of specific technologies, particularly those involving alternative sources of energy such as biomass, renewable resources for generation of electric power, advanced processes for generation from coal, and nuclear power. A key objective of the AEF series of reports is thus to help resolve conflicting analyses and to facilitate the charting of a new direction in the nation's energy enterprise.
    The AEF project, outlined in Appendix B, included a study committee and three panels that together have produced an extensive analysis of energy technology options for consideration in an ongoing national dialogue. A milestone in the project was the March 2008 "National Academies Summit on America's Energy Future" at which principals of related recent studies provided input to the AEF study committee and helped to inform the panels' deliberations. A report chronicling the event, The National Academies Summit on America's Energy Future: Summary of a Meeting, was published in October 2008.

37. Sigman, Daniel, P. J. DiFiore, M. P. Hain, C. Deutsch, Y. Wang, D. Karl, T. R. Knutson, K. K. Lehman, and S. Pantoja, 2009: The dual isotopes of deep nitrate as a constraint on the cycle and budget of oceanic fixed nitrogen. Deep Sea Research I, 56(9), doi:10.1016/j.dsr.2009.04.007 1419-1439
    [ Abstract ]

    We compare the output of an 18-box geochemical model of the ocean with measurements to investigate the controls on both the mean values and variation of nitrate δ¹⁵N and &delta:¹⁸O in the ocean interior. The &delta:¹⁸O of nitrate is our focus because it has been explored less in previous work. Denitrification raises the δ¹⁵N and &delta:¹⁸O of mean ocean nitrate by equal amounts above their input values for N₂ fixation (for δ¹⁵N) and nitrification (for &delta:¹⁸O), generating parallel gradients in the δ¹⁵N and &delta:¹⁸O of deep ocean nitrate. Partial nitrate assimilation in the photic zone also causes equivalent increases in the δ¹⁵N and &delta:¹⁸O of the residual nitrate that can be transported into the interior. However, the regeneration and nitrification of sinking N can be said to decouple the N and O isotopes of deep ocean nitrate, especially when the sinking N is produced in a low latitude region, where nitrate consumption is effectively complete. The δ¹⁵N of the regenerated nitrate is equivalent to that originally consumed, whereas the regeneration replaces nitrate previously elevated in &delta:¹⁸O due to denitrification or nitrate assimilation with nitrate having the &delta:¹⁸O of nitrification. This lowers the &delta:¹⁸O of mean ocean nitrate and weakens nitrate &delta:¹⁸O gradients in the interior relative to those in δ¹⁵N. This decoupling is characterized and quantified in the box model, and agreement with data shows its clear importance in the real ocean. At the same time, the model appears to generate overly strong gradients in both &delta:¹⁸O and δ¹⁵N within the ocean interior and a mean ocean nitrate &delta:¹⁸O that is higher than measured. This may be due to, in the model, too strong an impact of partial nitrate assimilation in the Southern Ocean on the δ¹⁵N and &delta:¹⁸O of preformed nitrate and/or too little cycling of intermediate-depth nitrate through the low latitude photic zone.

38. Socolow, Robert H., and Alexander Glaser, September 2009: Balancing risks: nuclear energy & climate change. Dædalus, Cambridge, MA, MIT Press for the American Academy of Arts & Sciences, 138(4), doi:10.1162/daed.2009.138.4.31 31-44
    [ Abstract ]

    Nuclear power could make a significant contribution to climate change mitigation. To do so, however, nuclear power must be deployed extensively in many developing countries that increasingly share production and consumption patterns with the industrialized world. Some of these countries are politically unstable today. If nuclear power is sufficiently unattractive in such a deployment scenario, nuclear power is not on the list of solutions to climate change.
    
    Nuclear power will not benefit climate change if its contribution is withdrawn a decade or two after global scale-up begins, as a result of the coupling of nuclear power to nuclear weapons. The coupling of nuclear power to nuclear weapons is the most critical flaw of nuclear power today and is the result of nuclear power's inadequate system of international governance and its reliance on uranium enrichment plants and reprocessing plants under national control.
    
    A world considerably safer for nuclear power could emerge as a co- benefit of the nuclear disarmament process. A multilateral nuclear disarmament process might be the most effective way-perhaps the only way-for states to decouple nuclear power from nuclear weapons.
    
    The next decade is critical. It can used to establish international ownership of uranium enrichment, the cessation of all spent fuel reprocessing, and much more effective norms of international governance.
    
    Every "solution" to climate change can be done badly or well. Done badly, solutions can be worse than the disease. Making climate change the world's exclusive priority is therefore dangerous. Conceding that such conclusions can embody only the most subjective of considerations, we judge the hazard of aggressively pursuing a global expansion of nuclear power today to be worse than the hazard of slowing the attack on climate change by whatever increment such caution entails. If over the next decade the world demonstrates that it can do nuclear power well, a global expansion of nuclear power would have to be -- indeed, should be -- seriously reexamined.

39. Tilman, D., Robert H. Socolow, J. A. Foley, J. Hill, Eric Larson, L. R. Lynd, Stephen W. Pacala, J. Reilly, Timothy Searchinger, C. Sommerville, and Robert H. Williams, July 2009: Beneficial Biofuels - The Food, Energy, and Environment Trilemma. Science, Washington, D.C., American Association for the Advancement of Science, 325(5938), doi:10.1126/science.1177970 270-271
    [ Abstract ]

    Exploiting multiple feedstocks, under new policies and accounting rules, to balance biofuel production, food security, and greenhouse-gas reduction.
    Dramatic improvements in policy and technology are needed to meet global demand for both food and biofuel feedstocks.

40. Tol, R.S.J., Robert H. Socolow, and Stephen W. Pacala, 2009: Understanding Long-Term Energy Use and Carbon Dioxide Emissions in the USA. Journal of Policy Modeling, 31, doi:10.1016/j.jpolmod.2008.12.002 425-445
    [ Abstract ]

    Energy is at the core of some of the greatest environmental and geopolitical challenges of our time. Cheap and plentiful energy – deemed necessary for our current standard of living – can at the moment only be supported by oil and coal, which pollutes the air, changes the climate, and, in the case of oil and gas, comes from unstable regions. Besides stimulating less polluting energy sources, it is important to improve the overall energy efficiency of the economy through technological, behavioural and other changes. For that, one needs to understand how and why energy use has changed in the past. This paper contributes to that.

41. Williams, Robert H., Eric Larson, Guangjian Liu, and Thomas Kreutz, 2009: Fischer-Tropsch Fuels from Coal and Biomass: Strategic Advantages of Once-Through (‘Polygeneration’) Configurations. Energy Procedia, 1(1), doi:10.1016/j.egypro.2009.02.252 4379-4386
    [ Abstract ]

    Systems that produce synthetic liquid fuels and electricity from coal and biomass with carbon capture and storage offer an attractive cost-competitive approach for decarbonising liquid fuels and electricity simultaneously.

42. Williams, Robert H., November 2009: Strategy Already Exists to Address CO₂ Emissions. Grand Forks Herald, http://www.gpisd.net/vertical/Sites/%7B1510F0B9-E3E3-419,
43. Xu, Y., Robert H. Williams, and Robert H. Socolow, 2009: China’s rapid deployment of SO₂ scrubbers. Energy and Environmental Science, 2, doi:10.1039/B901357C 459-465
    [ Abstract ]

    Details are gradually emerging regarding China’s extraordinary commitment to environmental technology that began in 2006. With the help of Chinese written references and some field verification, we tell here the story of the rapid deployment of sulfur dioxide scrubbers at coal power plants in 2006 and 2007. Scrubbers were installed in each of these years at plants with more than 100 000 megawatts of total generating capacity, overtaking the rate of construction of new coal power plants. Scrubber installation in each year equaled the entire scrubber capacity in the U.S. We also describe novel policies enacted by China in 2007 to increase the likelihood that installed scrubbers actually operate.

44. Xu, Y., J. M. Boucher, and Francois Morel, 2009: Expression and Diversity of Alkaline Phosphatase EHAP1 in Emiliania Huxleyi (Prymnesiophyceae). Journal of Phycology, 46(1), doi:10.1111/j.1529-8817.2009.00788.x 85-92
    [ Abstract ]

    Emiliania huxleyi (Lohmann) W. W. Hay et H. Mohler is a cosmopolitan coccolithophore species that forms massive blooms in low phosphorus seawater, partly due to its ability to utilize organic phosphate via extracellular alkaline phosphatase (AP). A novel AP gene, ehap1, was identified from the strain CCMP374. In this study, we examined the expression of ehap1 in various E. huxleyi strains and its genetic diversity in those strains and field populations. Two EHAP1 proteins (EHAP1a, 75 kDa and EHAP1b, 110 kDa) with virtually identical sequence were expressed under P limitation in all strains except one; a third protein (EHAP1c, 115 kDa) was expressed in a few strains. The correlation between AP activity and protein abundance suggests that EHAP1b is inactive and probably the precursor of EHAP1a. The transcript of ehap1 was induced by P depletion in all strains. The ehap1 gene sequence is highly conserved in these strains and field populations with <3% nucleic acid substitution. Most of the ehap1 sequences from one site in the English Channel and three sites in the Gulf of Alaska were essentially identical to one another. No EHAP1-like protein can be detected in other phytoplankton species tested via Western blot analysis. The rapid induction and high activity of EHAP1 in E. huxleyi suggest that it plays a significant role in P regeneration in the oligotrophic ocean where E. huxleyi is abundant. The EHAP1 antibody and gene-specific primers are well suited to study the dynamics of P limitation in field populations of E. huxleyi.

45. Baehr, J., D. McInerney, Klaus Keller, and J. Marotzke, 2008: Optimization of an observing system design for the North Atlantic meridional overturning circulation. Journal of Atmospheric and Oceanic Technology, 25(4), doi:10.1175/2007JTECHO535.1 625-634
    [ Abstract ]

    Three methods are analyzed for the design of ocean observing systems to monitor the meridional over-turning circulation (MOC) in the North Atlantic. Specifically, a continuous monitoring array to monitor the MOC at 1000 m at different latitudes is "deployed" into a numerical model. The authors compare array design methods guided by (i) physical intuition (heuristic array design), (ii) sequential optimization, and (iii) global optimization. The global optimization technique can recover the true global solution for the analyzed array design, while gradient-based optimization would be prone to misconverge. Both global optimization and heuristic array design yield considerably improved results over sequential array design. Global optimization always outperforms the heuristic array design in terms of minimizing the root-mean-square error. However, whether the results are physically meaningful is not guaranteed; the apparent success might merely represent a solution in which misfits compensate for each other accidentally. Testing the solution gained from global optimization in an independent dataset can provide crucial information about the solution's robustness.

46. Brennan, C. E., R. J. Matear, and Klaus Keller, 2008: Measuring oxygen concentrations improves the detection capabilities of an ocean circulation observation array. Journal of Geophysical Research – Oceans, 113(C02019), doi:10.1029/2007JC004113
    [ Abstract ]

    The North Atlantic meridional overturning circulation (MOC) may weaken or even collapse in response to anthropogenic climate forcing, with potentially nontrivial socioeconomic impacts. One currently implemented MOC observation system uses temperature and salinity (as well as other) observations along a zonal transect in the North Atlantic. The resulting MOC estimate has, however, a relatively low signal-to-noise ratio due to large internal variability and observation errors. Observations of hydrographic tracers that are mechanistically linked to MOC changes may increase the signal-to-noise ratio. A MOC slowdown is associated in model simulations with a shoaling of the boundary between North Atlantic Deep Water and Antarctic Bottom Water. This shoaling results in detectable trends in water mass tracers. Here we deploy a virtual observation array into a numerical model starting in model year 2006 to test whether observing the apparent oxygen utilization (AOU) in addition to the MOC estimate improves detection capabilities. Our detection method accounts for observation errors, autocorrelated variability, and uncertainty about the initial conditions. Neglecting the effects of observation errors and the uncertainty about the initial conditions results in artificially early detection times. The MOC signal alone enables reliable detection in roughly five decades. Adding AOU observations reduces this detection time by approximately 40%.

47. Crutzen, P., and Michael Oppenheimer, 2008: Learning about ozone depletion. Climatic Change, 89(1-2), doi:10.1007/S10584-008-9400-6 143-154
    [ Abstract ]

    Stratospheric ozone depletion has been much studied as a case history in the interaction between environmental science and environmental policy. The positive influence of science on policy is often underscored, but here we review the photochemistry of ozone in order to illustrate how scientific learning has the potential to mislead policy makers. The latter may occur particularly in circumstances where limited observations are combined with simplified models of a complex system, such as may generally occur in the global change arena. Even for the well-studied case of ozone depletion, further research is needed on the dynamics of scientific learning, particularly the scientific assessment process, and how assessments influence the development of public policy.

48. De Lorenzo, L., Thomas Kreutz, P. Chiesa, and Robert H. Williams, 2008: Carbon-free Hydrogen and Electricity from Coal: Options for Syngas Cooling in Systems Using a Hydrogen Separation Membrane Reactor. Proceedings of ASME Turbo Expo 2005, Reno, NV, June 6-9, 2005, 130(3), doi:10.1115/1.2795763
    [ Abstract ]

    Conversion of coal to carbon-free energy carriers, H₂ and electricity, with CO₂ capture and storage may have the potential to satisfy at a comparatively low cost much of the energy requirements in a carbon-constrained world. In a set of recent studies, we have assessed the thermodynamic and economic performance of numerous coal-to-H₂ plants that employ O₂-blown, entrained-flow gasification and sour water-gas shift (WGS) reactors, examining the effects of system pressure, syngas cooling via quench versus heat exchangers, “conventional” H₂ separation via pressure swing adsorption versus novel membrane-based approaches, and various gas turbine technologies for generating coproduct electricity. This study focuses on the synergy between H₂ separation membrane reactors (HSMRs) and syngas cooling with radiant and convective heat exchangers; such “syngas coolers” invariably boost system efficiency over that obtained with quenchcooled gasification. Conventional H₂ separation requires a relatively high steam-tocarbon ratio (S/C) to achieve a high level of H₂ production, and thus is well matched to relatively inefficient quench cooling. In contrast, HSMRs shift the WGS equilibrium by continuously extracting reaction product H₂, thereby allowing a much lower S/C ratio and consequently a higher degree of heat recovery and (potentially) system efficiency. We first present a parametric analysis illuminating the interaction between the syngas coolers, high temperature WGS reactor, and HSMR. We then compare the performance and cost of six different plant configurations, highlighting (1) the relative merits of the two syngas cooling methods in membrane-based systems, and (2) the comparative performance of conventional versus HSMR-based H₂ separation in plants with syngas coolers.

49. Fullerton, Don, and S.-R. Kim, 2008: Environmental Investment and Policy with Distortionary Taxes and Endogenous Growth. Journal of Environmental Economics and Management, 56(2), 141-154
    [ Abstract ]

    Recent studies consider public R&D spending that affects abatement knowledge and endogenous growth, distortionary taxes that affect capital formation, pollution taxes that affect environmental degradation, and regeneration that restores natural capital. Our model combines all those elements. The combination affects prior results, focusing on two parameters: the need for distorting taxes, and productivity of abatement knowledge relative to pollution. First, these two extensions can reverse prior findings that pollution tax revenue is always enough to pay for public R&D. Second, tax distortions and externalities alter prior findings that the ratio of public to private capital depends only on output elasticities. Third, dynamics affect prior static findings about other public spending “crowding out” environmental public goods. Fourth, a greater need for public spending can lead to greater increases in distorting taxes or pollution taxes. Fifth, greater environmental regulation can mean growth is higher or lower, even if welfare is higher.

50. Keller, Klaus, and D. McInerney, 2008: The dynamics of learning about a climate threshold. Climate Dynamics, 30(2-3), doi:10.1007/s00382-007-0290-5 321-332
    [ Abstract ]

    Anthropogenic greenhouse gas emissions may trigger threshold responses of the climate system. One relevant example of such a potential threshold response is a shutdown of the North Atlantic meridional overturning circulation (MOC). Numerous studies have analyzed the problem of early MOC change detection (i.e., detection before the forcing has committed the system to a threshold response). Here we analyze the early MOC prediction problem. To this end, we virtually deploy an MOC observation system into a simple model that mimics potential future MOC responses and analyze the timing of confident detection and prediction. Our analysis suggests that a confident prediction of a potential threshold response can require century time scales, considerably longer that the time required for confident detection. The signal enabling early prediction of an approaching MOC threshold in our model study is associated with the rate at which the MOC intensity decreases for a given forcing. A faster MOC weakening implies a higher MOC sensitivity to forcing. An MOC sensitivity exceeding a critical level results in a threshold response. Determining whether an observed MOC trend in our model differs in a statistically significant way from an unforced scenario (the detection problem) imposes lower requirements on an observation system than the determination whether the MOC will shut down in the future (the prediction problem). As a result, the virtual observation systems designed in our model for early detection of MOC changes might well fail at the task of early and confident prediction. Transferring this conclusion to the real world requires a considerably refined MOC model, as well as a more complete consideration of relevant observational constraints.

51. Keller, Klaus, G. Yohe, and M. Schlesinger, 2008: Managing the Risks of Climate Thresholds: Uncertainties and Information Needs. Climatic Change, 91(1-2), doi:10.1007/s10584-006-9114-6 5-10
    [ Abstract ]

    Human activities are driving atmospheric greenhouse-gas concentrations beyond levels experienced by previous civilizations. The uncertainty surrounding our understanding of the resulting climate change poses nontrivial challenges for the design and implementation of strategies to manage the associated risks. One challenge stems from the fact that the climate system can react abruptly and with only subtle warning signs before climate thresholds have been crossed (Stocker 1999; Alley et al. 2003). Model predictions suggest that anthropogenic greenhouse-gas emissions increase the likelihood of crossing these thresholds (Cubasch and Meehl 2001; Yohe et al. 2006). Coping with deep uncertainty in our understanding of the mechanisms, locations, and impacts of climate thresholds presents another challenge. Deep uncertainty presents itself when the relevant range of systems models and the associated probability density functions for their parameterizations are unknown and/or when decision-makers strongly disagree on their formulations (Lempert 2002). Furthermore, the requirements for creating feasible observation and modeling systems that could deliver confident and timely prediction of impending threshold crossings are mostly unknown. These challenges put a new emphasis on the analysis, design, and implementation of Earth observation systems and strategies to manage the risks of potential climate threshold responses.

52. Keller, Klaus, D. McInerney, and David F. Bradford, 2008: Carbon dioxide sequestration: When and how much? Climatic Change, 88(3-4), doi:10.1007/s10584-008-9417-x 267-291
    [ Abstract ]

    Carbon dioxide (CO₂) sequestration has been proposed as a key component in technological portfolios for managing anthropogenic climate change, since it may provide a faster and cheaper route to significant reductions in atmospheric CO₂ concentrations than abating CO₂ production. However, CO₂ sequestration is not a perfect substitute for CO₂ abatement because CO₂ may leak back into the atmosphere (thus imposing future climate change impacts) and because CO₂ sequestration requires energy (thus producing more CO₂ and depleting fossil fuel resources earlier). Here we use analytical and numerical models to assess the economic efficiency of CO₂ sequestration and analyze the optimal timing and extent of CO₂ sequestration. The economic efficiency factor of CO₂ sequestration can be expressed as the ratio of the marginal net benefits of sequestering CO₂ and avoiding CO₂ emissions. We derive an analytical solution for this efficiency factor for a simplified case in which we account for CO₂ leakage, discounting, the additional fossil fuel requirement of CO₂ sequestration, and the growth rate of carbon taxes. In this analytical model, the economic efficiency of CO₂ sequestration decreases as the CO₂ tax growth rate, leakage rates and energy requirements for CO₂ sequestration increase. Increasing discount rates increases the economic efficiency factor. In this simple model, short-term sequestration methods, such as afforestation, can even have negative economic efficiencies. We use a more realistic integrated-assessment model to additionally account for potentially important effects such as learning-by-doing and socio-economic inertia on optimal strategies. We measure the economic efficiency of CO₂ sequestration by the ratio of the marginal costs of CO₂ sequestration and CO₂ abatement along optimal trajectories. We show that the positive impacts of investments in CO₂ sequestration through the reduction of future marginal CO₂ sequestration costs and the alleviation of future inertia constraints can initially exceed the marginal sequestration costs. As a result, the economic efficiencies of CO₂ sequestration can exceed 100% and an optimal strategy will subsidize CO₂ sequestration that is initially more expensive than abatement. The potential economic value of a feasible and acceptable CO₂ sequestration technology is equivalent – in the adopted utilitarian model – to a one-time investment of several percent of present gross world product. It is optimal in the chosen economic framework to sequester substantial CO₂ quantities into reservoirs with small or zero leakage, given published estimates of marginal costs and climate change impacts. The optimal CO₂ trajectories in the case of sequestration from air can approach the pre-industrial level, constituting geoengineering. Our analysis is silent on important questions (e.g., the effects of model and parametric uncertainty, the potential learning about these uncertainties, or ethical dimension of such geoengineering strategies), which need to be addressed before our findings can be translated into policy-relevant recommendations.

53. Kreutz, Thomas, Eric Larson, Guangjian Liu, and Robert H. Williams, 2008: Fischer-Tropsch Fuels from Coal and Biomass. Proceedings of the 25th Annual International Pittsburgh Coal Conference,
    [ Abstract ]

    The prospect of sustained high oil prices, the heavy dependence of the US on imports for meeting its oil needs, and Middle East turmoil have together catalyzed intense interest in secure domestic alternatives to oil for satisfying US transportation energy needs. Also, it is now highly likely that the US will soon put into place a serious carbon mitigation policy—in which the transportation sector, accounting for 1/3 of US GHG emissions from fossil fuel burning, is likely to get focused attention. The two most significant domestic supplies that might be mobilized to address these challenges are biomass and coal.
    Spurred by farm policy, biomass has long been a focus of development efforts that have focused on using food crops for making biofuels (primarily corn-based ethanol but also biodiesel derived from soybeans and canola). However, concerns about food price impacts [1] and indirect land use impacts of growing biomass for energy on croplands [2,3] have led to growing recognition that emphasis should be shifted instead to exploiting for energy mainly lignocellulosic feedstocks that don’t require use of food biomass for providing energy—such as various crop and forest residues and energy crops that can be grown on degraded lands. These options include cellulosic ethanol produced biochemically and synthetic fuels derived thermochemically via biomass gasification—so-called biomass to liquids (BTL) technologies. Renewable lignocellulosic biomass provided using modest fossil fuel inputs can be considered a nearly “carbon neutral” feedstock, since CO₂ released to the atmosphere is recycled via photosynthesis.
    Among BTL options the production of Fischer-Tropsch liquids (FTL) from biomass has been given considerable attention [4,5,6,7,8]. FTL offers as advantages over cellulosic ethanol the prospects that: (i) no significant transportation fuel infrastructure changes would be required for widespread use, (ii) the technology could plausibly come into widespread use more quickly than cellulosic ethanol, which needs considerably more development before it can be widely deployed, (iii) it can probably accommodate more easily the wide range of biomass feedstocks that are likely to characterize the lignocellulosic biomass supply - because gasification-based processes tend to more tolerant of feedstock heterogeneity than biochemical processes.
    Recent oil price increases have led to considerable interest in making synthetic fuels from coal—so called coal-to-liquid (CTL) fuels—in light of coal’s relatively low prices and the abundance of coal both in the US and in other world regions that are not politically volatile. Much of this attention has been focused on FTL [9,10,11,12]. Coal can do much to improve energy security if it is used to make FTL. Moreover, the synfuels provided would be cleaner than the crude oil products displaced (having essentially zero sulfur and other contaminants and ultralow aromatic content). Also, for FTL production via modern entrained flow gasifiers, the air pollutant emissions from the plant are extremely low. But synthetic fuels made from coal without capture and storage of by-product CO₂ result in net GHG emissions about double those from petroleum fuels. And even with CO₂ capture and storage (CCS), the net GHG emission rate would be no less than for the crude oil products displaced. This would not be an auspicious feature of CTL with CCS technology if society decides to pursue an energy future that avoids dangerous anthropogenic interference with climate—as is required by the UN Framework Convention on Climate Change; there is now near scientific consensus that this will require by mid-century deep reductions in GHG emissions worldwide relative to the current global GHG emission rate [13].
    One approach to this challenge is to identify negative GHG emissions opportunities that might offset the CTL emissions and emissions from other difficult-to-decarbonize energy sources. Among these are opportunities to provide FTL from biomass at strong negative GHG emission rates. A striking feature of FTL technology is that a natural part of the process is the production of a stream of pure CO₂, accounting for about ½ of the carbon in the feedstock. If this CO₂ were captured and stored via CCS for FTL derived from biomass, the biofuels produced would be characterized by strong negative GHG emissions, because of the geological storage of photosynthetic CO₂ [14]. However, sustainably-recovered biomass is expensive, and the size of the BTL facilities will be limited by the quantities of biomass that can be gathered in a single location—which implies high specific capital costs ($ per barrel/day).
    These challenges posed by the BTL-with-CCS option could be mitigated by co-processing biomass with coal in the same facility. The economies of scale inherent in coal conversion could thereby be exploited, the average feedstock cost would be lower than for a pure BTL plant, and if CCS were carried out at the facility, the negative CO₂ emissions associated with the biomass could offset the unavoidable positive emissions with coal, leading to FTLs with low, zero, or negative net emissions [15]. Since this CBTL-with-CCS idea was first introduced, there has been much government and industrial interest in the concept: (i) in 2007 an Air Force/National Energy Technology Laboratory study was released exploring the prospects that its 2016 goal for 16 alternative jet fuel supplies1 might be met via CBTL with CCS to the extent of reducing the GHG emission rate for the FTL so produced to 0.8 times the rate for the crude oil products displaced [17]; (ii) the CBTL with CCS concept got focused attention in a recent Western Governors’ Association Report on future transportation fuels [18]; (iii) the National Energy Technology Laboratory is carrying out a major study comparing a wide range of CTL, BTL, and CBTL options with and without CCS [19], and (iv) some synfuel project developers are pursing plans to incorporate biomass as a feedstock along with coal in future FTL projects—including an FTL plant with CCS being planned by Baard Energy on the Ohio River at Wellsville, Ohio, that would eventually produce 50,000 barrels per day of FTL with up to up to 30% biomass by weight [20].
    Despite the growing interest in using CCS and biomass along with coal in addressing simultaneously the energy insecurity and climate change challenges posed by fuels for transportation, there is not yet available a comprehensive analytical framework for deciding the most promising ways forward—including a systematic way of assessing: (i) BTL vs CBTL vs CTL options, (ii) the amounts of biomass that might be accommodated in CBTL systems, (iii) the appropriate scales for BTL and CBTL systems, (iv) the extent to which CO₂ capture might plausibly be pursued for all FTL systems derived from coal and/or biomass, and (v) prospective carbon policy impacts on FTL projects.
    This paper can be considered a first step toward addressing these issues. We present here a comprehensive analytical framework suitable for addressing these challenges and early results of applying this framework by making comparisons in a self-consistent manner of designs for 16 alternative CTL, BTL, and CBTL plants, with and without CCS, with regard to mass/energy/carbon balances and economics.

54. McInerney, D., and Klaus Keller, 2008: Economically optimal risk reduction strategies in the face of uncertain climate thresholds. Climatic Change, 91(1-2), doi:10.1007/s10584-006-9137-z 29-41
    [ Abstract ]

    Anthropogenic greenhouse gas emissions may trigger climate threshold responses, such as a collapse of the North Atlantic meridional overturning circulation (MOC). Climate threshold responses have been interpreted as an example of “dangerous anthropogenic interference with the climate system” in the sense of the United Nations Framework Convention on Climate Change (UNFCCC). One UNFCCC objective is to “prevent” such dangerous anthropogenic interference. The current uncertainty about important parameters of the coupled natural–human system implies, however, that this UNFCCC objective can only be achieved in a probabilistic sense. In other words, climate management can only reduce – but not entirely eliminate – the risk of crossing climate thresholds. Here we use an integrated assessment model of climate change to derive economically optimal risk-reduction strategies. We implement a stochastic version of the DICE model and account for uncertainty about four parameters that have been previously identified as dominant drivers of the uncertain system response. The resulting model is, of course, just a crude approximation as it neglects, for example, some structural uncertainty, and focuses on a single threshold, out of many potential climate responses. Subject to this caveat, our analysis suggests five main conclusions. First, reducing the numerical artifacts due to sub-sampling the parameter probability density functions to reasonable levels requires sample sizes exceeding 10³. Conclusions of previous studies that are based on much smaller sample sizes may hence need to be revisited. Second, following a business-as-usual (BAU) scenario results in odds for an MOC collapse in the next 150 years exceeding 1 in 3 in this model. Third, an economically “optimal” strategy (that maximizes the expected utility of the decision-maker) reduces carbon dioxide (CO₂) emissions by approximately 25% at the end of this century, compared with BAU emissions. Perhaps surprisingly, this strategy leaves the odds of an MOC collapse virtually unchanged compared to a BAU strategy. Fourth, reducing the odds for an MOC collapse to 1 in 10 would require an almost complete decarbonization of the economy within a few decades. Finally, further risk reductions (e.g., to 1 in 100) are possible in the framework of the simple model, but would require faster and more expensive reductions in CO₂ emissions.

55. Mignone, B. K., Robert H. Socolow, Jorge Sarmiento, and Michael Oppenheimer, 2008: Atmospheric Stabilization and the Timing of Carbon Mitigation. Climatic Change, 88(3-4), doi:10.1007/S10584-007-9391-8 251-265
    [ Abstract ]

    Stabilization of atmospheric CO₂ concentrations below a pre-industrial doubling (~550 ppm) is a commonly cited target in climate policy assessment. When the rate at which future emissions can fall is assumed to be fixed, the peak atmospheric concentration – or the stabilization “frontier” – is an increasing and convex function of the length of postponement. Here we find that a decline in emissions of 1% year⁻¹ beginning today would place the frontier near 475 ppm and that when mitigation is postponed, options disappear (on average) at the rate of ~9 ppm year⁻¹, meaning that delays of more than a decade will likely preclude stabilization below a doubling. When constraints on the future decline rate of emissions are relaxed, a particular atmospheric target can be realized in many ways, with scenarios that allow longer postponement of emissions reductions requiring greater increases in the intensity of future mitigation. However, the marginal rate of substitution between future mitigation and present delay becomes prohibitively large when the balance is shifted too far toward the future, meaning that some amount of postponement cannot be fully offset by simply increasing the intensity of future mitigation. Consequently, these results suggest that a practical transition path to a given stabilization target in the most commonly cited range can allow, at most, one or two decades of delay.

56. Oppenheimer, Michael, B. O'Neill, and M. Webster, 2008: Negative Learning. Climatic Change, 89(1-2), doi:10.1007/S10584-008-9405-1 155-172
    [ Abstract ]

    New technical information may lead to scientific beliefs that diverge over time from the a posteriori right answer. We call this phenomenon, which is particularly problematic in the global change arena, negative learning. Negative learning may have affected policy in important cases, including stratospheric ozone depletion, dynamics of the West Antarctic ice sheet, and population and energy projections. We simulate negative learning in the context of climate change with a formal model that embeds the concept within the Bayesian framework, illustrating that it may lead to errant decisions and large welfare losses to society. Based on these cases, we suggest approaches to scientific assessment and decision making that could mitigate the problem. Application of the tools of science history to the study of learning in global change, including critical examination of the assessment process to understand how judgments are made, could provide important insights on how to improve the flow of information to policy makers.

57. Perry, William, Alec Broers, Farouk El-Baz, and Robert H. Socolow, 2008: Grand Challenges for Engineering. National Academy of Sciences, http://www.engineeringchallenges.org/?ID=11574,
    [ Abstract ]

    A diverse committee of experts from around the world, some of the most accomplished engineers and scientists of their generation, proposed the 14 challenges outlined in this booklet. The panel, which was convened by the U.S. National Academy of Engineering (NAE) at the request of the U.S. National Science Foundation, did not rank the challenges selected, nor did it endorse particular approaches to meeting them. Rather than attempt to include every important goal for engineering, the panel chose opportunities that were both achievable and sustainable to help people and the planet thrive. The panel’s conclusions were reviewed by more than 50 subject-matter experts. In addition, the effort received worldwide input from prominent engineers and scientists, as well as from the general public. The NAE is offering an opportunity to comment on the challenges via the project’s interactive Web site at www.engineeringchallenges.org.

58. Socolow, Robert H., 2008: Stabilization Wedges and Climate Change. Physics of Sustainable Energy: Using Energy Efficiently and Producing It Renewably. AIP Conf. Proc., 1044, doi:10.1063/1.2993727 28-48
    [ Abstract ]

    An informal pedagogical tour provides quantitative views of the magnitude of the challenge of mitigating climate change and many of the energy technologies available to address this challenge. The importance of energy efficiency is emphasized, as is the societal context for technological change.

59. Socolow, Robert H., 2008: The Critical Role of Energy Efficiency in Mitigating Global Warming. Government Law and Policy Journal, NY State Bar Association, Albany, NY, http://www.princeton.edu/mae/people/faculty/socolow/SocolownybarGLPJSum08.pdf, 10(1),
    [ Abstract ]

    This is the written version of a lecture presented to the Public Service Commission, State of New York, Proceeding on Motion of the Commission Regarding an Energy Efficiency Portfolio Standard. The lecture was given at the Albany Law School, Albany, New York, July 19, 2007.
    
    This is reprinted with permission from the Government Law and Policy Journal.

60. Succar, Samir, and Robert H. Williams, April 2008: Compressed Air Energy Storage: Theory, Resources, and Applications For Wind Power. Energy Systems Analysis Group, Princeton Environmental Institute, Princeton, NJ, http://www.princeton.edu/~cmi/research/Capture/Papers/SuccarWilliams_PEI_CAES_2008April8.pdf,
    [ Abstract ]

    This report reviews the literature on compressed air energy storage (CAES) and synthesizes the information in the context of electricity production for a carbon constrained world.
    
    CAES has historically been used for grid management applications such as load shifting and regulation control. Although this continues to be the dominant near-term market opportunity for CAES, future climate policies may present a new application: the production of baseload electricity from wind turbine arrays coupled to CAES.
    
    Previous studies on the combination of wind and CAES have focused on economics and emissions [1-10]. This report highlights these aspects of baseload wind/CAES systems, but focuses on the technical and geologic requirements for widespread deployment of CAES, with special attention to relevant geologies in wind-rich regions of North America.
    
    Large penetrations of wind/CAES could make substantial contributions in providing electricity with near-zero GHG emissions if several issues can be adequately addressed. Drawing on the results of previous field tests and feasibility studies as well as the existing literature on energy storage and CAES, this report outlines these issues and frames the need for further studies to provide the basis for estimating the true potential of wind/CAES.

61. Succar, Samir, September 2008: Baseload Power Production from Wind Turbine Arrays Coupled to Compressed Air Energy Storage. Ph.D. Thesis, Department of Electrical Engineering, Princeton University, http://proquest.umi.com/pqdlink?Ver=1&Exp=10-04-2014&FMT=7&DID=1594486331&RQT=309&attempt=1&,
    [ Abstract ]

    An analysis is presented of compressed air energy storage (CAES) and its potential for mitigating the intermittency of wind power, facilitating access to remote wind resources and transforming wind into baseload power. Although CAES has traditionally served other grid support applications, it is also well suited for wind balancing applications due its ability to provide long duration storage, its fast ramp rates and its high part load efficiencies. In addition, geologies potentially suitable for CAES appear to be abundant in regions with high- quality wind resources. This is especially true of porous rock formations, which have the potential to be the least costly air storage option for CAES. The characteristics of formations suitable for CAES storage and the challenges associated with using air as a storage fluid are discussed. An optimization framework is developed for analyzing the cost of baseload plants comprised of wind turbine arrays backed by natural gas-fired generating capacity and/or CAES. The optimization model analyzes changes to key aspects of the system configuration such as the wind turbine rating, the relative capacities of the system components, the size of the CAES storage reservoir and the wind turbine spacing. The response of the optimal system configuration to changes in natural gas price, greenhouse gas (GHG) emissions price, capital cost, and wind resource is also considered. Wind turbine rating is given focused attention because of its substantial impact on system configuration and output behavior. The generation cost of baseload wind is compared to that of other baseload options. To highlight the carbon-mitigation potential of baseload wind, the competition with coal power (with and without CO₂ capture and storage, CCS) is given prominent attention. The ability of alternative options to compete under dispatch competition is explored thereby clarifying the extent to which baseload wind can defend high capacity factors in the market. This analysis indicates that CAES might be well suited for balancing wind power output and enabling wind to achieve deep reductions in GHG emissions from power generation globally.

62. Chu, S., J. Goldenberg, S. Arungu Olende, M. El-Ashry, G. Davis, T. B. Johansson, D. W. Keith, J. Li, N. Nakicenovic, R. Pachauri, M. Shafie-Pour, E. Shpilrain, Robert H. Socolow, K. Yamaji, and L. Yan, October 2007: Lighting the way - Toward a sustainable energy future. A Report to the InterAcademy Council, http://royalsociety.org/downloaddoc.asp?id=4695,
    [ Abstract ]

    Making the transition to a sustainable energy future is one of the central challenges humankind faces in this century. The concept of energy sustainability encompasses not only the imperative of securing adequate energy to meet future needs, but doing so in a way that (a) is compatible with preserving the underlying integrity of essential natural systems, including averting dangerous climate change; (b) extends basic energy services to the more than 2 billion people worldwide who currently lack access to modern forms of energy; and (c) reduces the security risks and potential for geopolitical conflict that could otherwise arise from an escalating competition for unevenly distributed energy resources.

63. Donner, S. D., T. R. Knutson, and Michael Oppenheimer, 2007: Model-based assessment of the role of human-induced climate change in the 2005 Caribbean coral bleaching event. Proceedings of the National Academy of Sciences of the United States of America, 104(13), doi:10.1073/pnas.0610122104 5483-5488
    [ Abstract ]

    Episodes of mass coral bleaching around the world in recent decades have been attributed to periods of anomalously warm ocean temperatures. In 2005, the sea surface temperature (SST) anomaly in the tropical North Atlantic that may have contributed to the strong hurricane season caused widespread coral bleaching in the Eastern Caribbean. Here, we use two global climate models to evaluate the contribution of natural climate variability and anthropogenic forcing to the thermal stress that caused the 2005 coral bleaching event. Historical temperature data and simulations for the 1870–2000 period show that the observed warming in the region is unlikely to be due to unforced climate variability alone. Simulation of background climate variability suggests that anthropogenic warming may have increased the probability of occurrence of significant thermal stress events for corals in this region by an order of magnitude. Under scenarios of future greenhouse gas emissions, mass coral bleaching in the Eastern Caribbean may become a biannual event in 20–30 years. However, if corals and their symbionts can adapt by 1– 1.5°C, such mass bleaching events may not begin to recur at potentially harmful intervals until the latter half of the century. The delay could enable more time to alter the path of greenhouse gas emissions, although long-term ‘‘committed warming’’ even after stabilization of atmospheric CO₂ levels may still represent an additional long-term threat to corals.

64. Gloor, M. N., E. Dlugokensky, C. Brenninkmeijer, L. W. Horowitz, D. F. Hurst, G. Dutton, C. Crevoisier, T. Machida, and P. P. Tans, 2007: Three-dimensional SF₆ data and tropospheric transport simulations: Signals, modeling accuracy, and implications for inverse modeling. Journal of Geophysical Research, 112(D15112), doi:10.1029/2006JD007973
    [ Abstract ]

    Surface emissions of SF₆ are closely tied to human activity and thus fairly well known. They therefore can and have been used to evaluate tropospheric transport predicted by models. A range of new atmospheric SF₆ data permit us to expand on earlier studies. The purpose of this first of two papers is to characterize known and new transport constraints provided by the data and to use them to quantify predictive skill of the MOZART-2 atmospheric chemistry and transport model. Main noteworthy observational constraints are (1) a well-known steep N-S gradient at the surface confined to an ≈40° wide latitude band in the tropics; (2) a fairly uniform N-S gradient in the upper troposphere; (3) an increase in the temporal variation in upper troposphere Northern Hemisphere records with increasing latitude; (4) a negative SF₆ gradient in Northern Hemisphere vertical profiles from the surface to 8 km height, but a positive gradient in the Southern Hemisphere; and (5) a clear reflection in surface records of large-scale seasonal atmosphere movements like the undulations of the Intertropical Convergence Zone (ITCZ). Comparison of observations with simulations reveal excellent modeling skills with regards to (1) large-scale annual mean latitudinal gradients at remote surface sites (relative bias of N-S hemisphere difference ≤ 5%) and aloft (≈10 km, relative bias ≤ 25%); (2) seasonality in signals at remote sites caused by large-scale movements of the atmosphere; (3) time variation in upper troposphere records; (4) ‘‘faithfulness’’ of advective transport on timescales up to ≈1 week; and (5) the general shapes and seasonal variation of vertical profiles. The model (1) underestimates the variation in the vertical of profiles, particularly those from locations close to high emissions regions, and (2) overestimates the difference in SF₆ between the planetary boundary layer (PBL) and free troposphere over North America, and thus likely Eurasia, during winter by approximately a factor of 2 (STD ≈ 100%). The comparisons permit estimating lower bounds on representation errors which are large for sites close to continental outflow regions. Given the magnitude of the signals and signal variance, SF₆ provides a strong constraint on interhemispheric transport, PBL ventilation, dispersion pathways of northern midlatitude surface emissions through the upper troposphere, and large-scale movements of the atmosphere.

65. Greenblatt, J. B., Samir Succar, D. C. Denkenberger, Robert H. Williams, and Robert H. Socolow, 2007: Baseload wind energy: Modeling the competition between gas turbines and compressed air energy storage for supplemental generation. Energy Policy, 35(3), doi:10.1016/j.enpol.2006.03.023 1474-1492
    [ Abstract ]

    The economic viability of producing baseload wind energy was explored using a cost-optimization model to simulate two competing systems: wind energy supplemented by simple- and combined cycle natural gas turbines (‘‘wind+gas’’), and wind energy supplemented by compressed air energy storage (‘‘wind+CAES’’). Pure combined cycle natural gas turbines (‘‘gas’’) were used as a proxy for conventional baseload generation. Long-distance electric transmission was integral to the analysis. Given the future uncertainty in both natural gas price and greenhouse gas (GHG) emissions price, we introduced an effective fuel price, p_NGeff, being the sum of the real natural gas price and the GHG price. Under the assumption of p_NGeff = $5/GJ (lower heating value), 650W/m² wind resource, 750km transmission line, and a fixed 90% capacity factor, wind+CAES was the most expensive system at ¢6.0/kWh, and did not break even with the next most expensive wind+gas system until p_NGeff = $9.0/GJ. However, under real market conditions, the system with the least dispatch cost (short-run marginal cost) is dispatched first, attaining the highest capacity factor and diminishing the capacity factors of competitors, raising their total cost. We estimate that the wind+CAES system, with a greenhouse gas (GHG) emission rate that is onefourth of that for natural gas combined cycle plants and about one-tenth of that for pulverized coal plants, has the lowest dispatch cost of the alternatives considered (lower even than for coal power plants) above a GHG emissions price of $35/tC_equiv., with good prospects for realizing a higher capacity factor and a lower total cost of energy than all the competing technologies over a wide range of effective fuel costs. This ability to compete in economic dispatch greatly boosts the market penetration potential of wind energy and suggests a substantial growth opportunity for natural gas in providing baseload power via wind+CAES, even at high natural gas prices.

66. Keller, Klaus, L. I. Miltich, A. Robinson, and R.S.J. Tol, 2007: How Overconfident are Current Projections of Anthropogenic Carbon Dioxide Emissions? Working Papers, Paper 39, http://www.bepress.com/cgi/viewcontent.cgi?article=1095&context=feem,
    [ Abstract ]

    Analyzing the risks of anthropogenic climate change requires sound probabilistic projections of CO₂ emissions. Previous projections have broken important new ground, but many rely on out-of-range projections, are limited to the 21^st century, or provide only implicit probabilistic information. Here we take a step towards resolving these problems by assimilating globally aggregated observations of population size, economic output, and CO₂ emissions over the last three centuries into a simple economic model. We use this model to derive probabilistic projections of business-as-usual CO₂ emissions to the year 2150. We demonstrate how the common practice to limit the calibration timescale to decades can result in biased and overconfident projections. The range of several CO₂ emission scenarios (e.g., from the Special Report on Emission Scenarios) misses potentially important tails of our projected probability density function. Studies that have interpreted the range of CO₂ emission scenarios as an approximation for the full forcing uncertainty may well be biased towards overconfident climate change projections.

67. Keller, Klaus, C. Deutsch, M. G. Hall, and David F. Bradford, 2007: Early detection of changes in the North Atlantic meridional overturning circulation: Implications for the design of ocean observation systems. Journal of Climate, 20, doi:10.1175/JCLI3993.1 145-157
    [ Abstract ]

    Many climate models predict that anthropogenic greenhouse gas emissions may cause a threshold response of the North Atlantic meridional overturning circulation (MOC). These model predictions are, however, uncertain. Reducing this uncertainty can have an economic value, because it would allow for the design of more efficient risk management strategies. Early information about the MOC sensitivity to anthropogenic forcing (i.e., information that arrives before the system is committed to a threshold response) could be especially valuable. Here the focus is on one particular kind of information: the detection of anthropogenic MOC changes. It is shown that an MOC observation system based on infrequent (decadal scale) hydrographic observations may well fail in the task of early MOC change detection. This is because this system observes too infrequently and the observation errors are too large. More frequent observations and reduced observation errors would result in earlier detection. It is also shown that the economic value of information associated with a confident and early prediction of an MOC threshold response could exceed the costs of typically implemented ocean observation systems by orders of magnitude. One open challenge is to identify a feasible observation system that would enable such a confident and early MOC prediction across the range of possible MOC responses.

68. Keller, Klaus, S.-R. Kim, J. Baehr, David F. Bradford, and Michael Oppenheimer, 2007: What is the economic value of information about climate thresholds? Human-Induced Climate Change: An Interdisciplinary Assessment, Cambridge University Press, Cambridge, MA, http://www.geosc.psu.edu/~kkeller/Keller_snowmass_pp_07.pdf, (Chapter 28), 343-354
    [ Abstract ]

    The field of integrated assessment of climate change is undergoing a paradigm shift towards the analysis of potentially abrupt and irreversible climate changes (Alley et al., 2003; Keller et al., 2006b). Early integrated studies broke important new ground in exploring the relationship between the costs and benefits of reducing carbon dioxide (CO₂) emissions (e.g., Nordhaus, 1991; Manne and Richels, 1991; or Tol, 1997). These studies project the climate response to anthropogenic CO₂ emissions to be relatively smooth and trypically conclude that the projected benefits of reducing CO₂ emissions would justify only small reductions in CO₂ emissions in a cost-benefit framework. The validity of the often-assumed smooth climate response is, however, questionable, given how that climate system has responded to forcing in the geological past. Before the Anthropocene, the geological time period where humans have started to influence the global biogeochemical cycles considerably (Crutzen, 2002) , the predominant responses of the climate system were forced by small changes in solar insolation occurring on timescales of thousands of years (Berger and Loutre, 1991). Yet this slow and smooth forcing apparently triggered abrupt climate changes - a threshold response where the climate system moved between different basins of attraction (Berger, 1990; Clement et al., 2001). Anthropogenic forcing may trigger climate threshold responses in the future (Alley et al., 2003; Keller et al., 2006b). Examples of such threshold responses include (i) a collapse of the North Atlantic meridional overturning circulation (Rahmstorf, 2000; Stommel, 1961), (ii) a disintegration of the West Antarctic Ice Sheet (Mercer, 1978; Oppenheimer, 1998), (iii) abrupt vegetation changes (Claussen et al., 1999; Scheffer et al., 2001), or (iv) changes in properties of the El Nino Southern Oscillation, ENSO (Fedorov and Philander, 2000; Timmermann, 201). Here we focus on the first two examples: a possible collapse of the North Atlantic meridional overturning circulation and a possible disintegration of the West Antarctic Ice Sheet. Our analysis address three main questions. (i) What underlying mechanisms define a climate threshold? (ii) What are the key scientific uncertainties in predicting whether these thresholds may be crossed in the future? (iii) What might be reasonable order-of-magnitude estimates of the expected economic value of reducing these uncertainties? Our analysis suggests that climate strategies designed to reduce the risk of crossing climate thresholds have to be designed in the face of large uncertainties. Some of the key uncertainties (e.g., the sensitivity of the meridional overturning circulation to anthropogenic greenhouse gas emissions) can be reduced by observation systems. We conclude by identifying future research needs.

69. Keller, Klaus, A. Robinson, David F. Bradford, and Michael Oppenheimer, 2007: The regrets of procrastination in climate policy. Environmental Research Letters, (Lett 2, No. 2), doi:10.1088/1748-9326/2/2/024004
    [ Abstract ]

    Anthropogenic carbon dioxide (CO₂) emissions are projected to impose economic costs due to the associated climate change impacts. Climate change impacts can be reduced by abating CO₂ emissions. What would be an economically optimal investment in abating CO₂ emissions? Economic models typically suggest that reducing CO₂ emissions by roughly ten to twenty per cent relative to business-as-usual would be an economically optimal strategy. The currently implemented CO₂ abatement of a few per cent falls short of this benchmark. Hence, the global community may be procrastinating in implementing an economically optimal strategy. Here we use a simple economic model to estimate the regrets of this procrastination—the economic costs due to the suboptimal strategy choice. The regrets of procrastination can range from billions to trillions of US dollars. The regrets increase with increasing procrastination period and with decreasing limits on global mean temperature increase. Extended procrastination may close the window of opportunity to avoid crossing temperature limits interpreted by some as ‘dangerous anthropogenic interference with the climate system’ in the sense of Article 2 of the United Nations Framework Convention on Global Climate Change.

70. Meng, K., Robert H. Williams, and Michael Celia, 2007: Opportunities for low-cost CO₂ storage demonstration projects in China. Energy Policy, 35(4), doi:10.1016/j.enpol.2006.08.016 2368-2378
    [ Abstract ]

    Several CO₂ storage demonstration projects are needed in a variety of geological formations worldwide to prove the viability of CO₂ capture and storage as a major option for climate change mitigation. China has several low-cost CO₂ sources at sites that produce NH₃ from coal via gasification. At these plants, CO₂ generated in excess of the amount needed for other purposes (e.g., urea synthesis) is vented as a relatively pure stream. These CO₂ sources would potentially be economically interesting candidates for storage demonstration projects if there are suitable storage sites nearby. In this study a survey was conducted to estimate CO₂ availability at modern Chinese coal-fed ammonia plants. Results indicate that annual quantities of available, relatively pure CO₂ per site range from 0.6 to 1.1 million tonnes. The CO₂ source assessment was complemented by analysis of possible nearby opportunities for CO₂ storage. CO₂ sources were mapped in relation to China’s petroliferous sedimentary basins where prospective CO₂ storage reservoirs possibly exist. Four promising pairs of sources and sinks were identified. Project costs for storage in deep saline aquifers were estimated for each pairing ranging from $15–21/t of CO₂. Potential enhanced oil recovery and enhanced coal bed methane recovery opportunities near each prospective source were also considered.

71. Naik, V., D. L. Mauzerall, L. W. Horowitz, M. D. Schwarzkopf, V. Ramaswamy, and Michael Oppenheimer, 2007: On the sensitivity of radiative forcing from biomass burning aerosols and ozone to emission location. Geophysical Research Letters, 34(L03818), doi:10.1029/2006GL028149
    [ Abstract ]

    Biomass burning is a major source of air pollutants, some of which are also climate forcing agents. We investigate the sensitivity of direct radiative forcing due to tropospheric ozone and aerosols (carbonaceous and sulfate) to a marginal reduction in their (or their precursor) emissions from major biomass burning regions. We find that the largest negative global forcing is for 10% emission reductions in tropical regions, including Africa (-4.1 mWm-2 from gas and -4.1 mWm-2 from aerosols), and South America (-3.0 mWmfrom gas and -2.8 mWmfrom aerosols). We estimate that a unit reduction in the amount of biomass burned in India produces the largest negative ozone and aerosol forcing. Our analysis indicates that reducing biomass burning emissions causes negative global radiative forcing due to ozone and aerosols; however, regional differences need to be considered when evaluating controls on biomass burning to mitigate global climate change.

72. Nævdal, E., and Michael Oppenheimer, 2007: The Economics of the Thermohaline Circulation – A Problem with Multiple Thresholds of Unknown Locations. Resource and Energy Economics, 27(4), doi:10.1016/j.reseneeco.2007.01.003 262-283
    [ Abstract ]

    A potentially serious environmental threat facing humanity is the possibility of a collapse of the thermohaline circulation. Resulting climate changes, including absolute cooling near Greenland and northwest Europe, could be abrupt. Collapse of the thermohaline circulation may be triggered if the temperature or the rate of temperature change exceeds certain thresholds. The locations of these thresholds are unknown. Economic regulation of this problem requires solution methods for a class of dynamic optimization problems with multiple thresholds located in n-dimensional space. This class of problems has hitherto not been discussed in the literature. We present a model for the economic regulation of CO₂ emissions in the presence of threshold-triggered risk of a collapsing thermohaline circulation and derive optimality conditions for regulation.

73. Oppenheimer, Michael, B. O'Neill, M. Webster, and S. Agrawala, 2007: Climate Change: The Limits of Consensus. Science, 317, doi:10.1126/science.1144831 1505-1506
    [ Abstract ]

    The Intergovernmental Panel on Climate Change (IPCC) has just delivered its Fourth Assessment Report (AR4) since 1990. The IPCC was a bold innovation when it was established, and its accomplishments are singular (1, 2). It was the conclusion in the IPCC First Assessment Report that the world is likely to see “a rate of increase of global mean temperature during the next century … that is greater than seen over the past 10,000 years” (3) that proved influential in catalyzing the negotiation of the United Nations Framework Convention on Climate Change. The conclusions of the Second Assessment with regard to the human influence on climate (4) marked a paradigm shift in the policy debate that contributed to the negotiation of the Kyoto Protocol. IPCC conclusions from the Third, and now the Fourth, assessments have further solidified consensus behind the role of humans in changing the earth’s climate.

74. Schneider, S. H., S. Semenov, A. Patwardhan, I. Burton, C.H.D. Magadza, Michael Oppenheimer, A. B. Pittock, A. Rahman, J. B. Smith, A. Suarez, and F. Yamin, 2007: Assessing Key Vulnerabilities and the Risk from Climate Change. Intergovernmental Panel on Climate Change, http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-chapter19.pdf, 19(Working Group II), 781-810
    [ Abstract ]

    Climate change will lead to changes in geophysical, biological and socio-economic systems.An impact describes a specific change in a system caused by its exposure to climate change. Impacts may be judged to be harmful or beneficial.Vulnerability to climate change is the degree to which these systems are susceptible to, and unable to cope with, adverse impacts. The concept of risk,which combines the magnitude of the impact with the probability of its occurrence, captures uncertainty in the underlying processes of climate change, exposure, impacts and adaptation. Many of these impacts, vulnerabilities and risks merit particular attention by policy-makers due to characteristics that might make them ‘key’. The identification of potential key vulnerabilities is intended to provide guidance to decision-makers for identifying levels and rates of climate change that may be associated with ‘dangerous anthropogenic interference’ (DAI) with the climate system, in the terminology of United Nations Framework Convention on Climate Change (UNFCCC) Article 2. Ultimately, the definition of DAI cannot be based on scientific arguments alone, but involves other judgements informed by the state of scientific knowledge. No single metric can adequately describe the diversity of key vulnerabilities, nor determine their ranking.

75. Sheppard, M. C., and Robert H. Socolow, 2007: Perspective (Cover Story, Invited): Sustaining Fossil Fuel Use in a Carbon-Constrained World by Rapid Commercialization of Carbon Capture and Sequestration. AIChe Journal, Hoboken, NJ, John Wiley and Sons, 53(12), doi:10.1002/aic.11356 3022-3028
    [ Abstract ]

    Briefly stated, carbon capture and sequestration (CCS) will allow us to sustain many of the benefits of access to hydrocarbons even in a carbon constrained world. Even where the CO₂ generated by burning hydrocarbon cannot be captured easily (as in the case of oil use for transportation), sequestration of CO₂ from other sources (e.g., coal fired power stations) can help create, to some degree, the ‘‘headroom’’ needed to allow for the volumes of CO₂ which escape capture. Because of the likely continuing competitive (direct) cost of hydrocarbons, and in light of the huge investment already made in infrastructure to deliver them, the combination of fossil fuel use with CCS is likely to be emphasized as a strong complement to strategies involving alternative, nonhydrocarbon sources of energy supply. Moreover, concerns about the security of supply of transportation fuels are likely to drive moves toward less conventional hydrocarbon sources (coal-to-liquids, unconventional oil and gas, etc.). However, the exploitation of heavy oil, tar sands, oil shales, and liquids derived from coal for transportation fuel comes with a significantly heavier burden of CO₂ than is associated with conventional oil and gas. CCS has the potential to mitigate some of this extra CO₂ burden, provided it is implemented broadly over the coming decades. Widespread use could continue beyond the end of the century.

76. Socolow, Robert H., January 2007: Facing new unknowns. Bulletin of the Atomic Scientists, Chicago, IL, Bulletin of the Atomic Scientists, 63(1), doi:10.2968/063001014 45-46
    [ Abstract ]

    THE BULLETIN'S ICONIC CLOCK CAPTURES more than the imminence of catastrophe. It signifies the transformative power of science, a planetary consciousness, and the ironies of moral behavior. All of these messages are of first-order importance in grappling with climate change.

77. Socolow, Robert H., and S. H. Lam, 2007: Good Enough Tools for Global Warming Policy Making. Philosophical Transactions of the Royal Society, 365, doi:10.1098/rsta.2006.1961 897-934
    [ Abstract ]

    We present a simple analysis of the global warming problem caused by the emissions of CO₂ (a major greenhouse gas) into the atmosphere resulting from the burning of fossil fuels. We provide quantitative tools which enable policymakers and interested citizens to explore the following issues central to the global warming problem. (i) At what rate are we permitted to continue to emit CO₂ after the global average atmospheric concentration has ‘stabilized’ at some chosen target level? The answer here provides the magnitude of the effort, measured by the necessary total reduction of today’s global (annual) emissions rate to achieve stabilization. We shall see that stabilized emissions rates for all interesting stabilized concentration levels are much lower than the current emissions rate, but these small finite values are very important. (ii) Across how many years can we spread the total effort to reduce the annual CO₂ emissions rate from its current high value to the above-mentioned low and stabilized target value? The answer here provides the time-scale of the total mitigation effort for any chosen atmospheric concentration target level. We confirm the common understanding that targets below a doubling of the pre-industrial concentration create great pressure to produce action immediately, while targets above double the pre-industrial level can tolerate longer periods of inaction. (iii) How much harder is the future mitigation effort, if we do not do our share of the job now? Is it a good idea to overshoot a stabilization target? The quantitative answers here provide the penalty of procrastination. For example, the mitigation task to avoid doubling the pre-industrial level is a problem that can be addressed gradually, over a period extending more than a century, if started immediately, but procrastination can turn the effort into a much more urgent task that extends over only a few decades. We also find that overshooting target levels is a bad idea. The quality of public discourse on this subject could be much enhanced if ball-park quantitative answers to these questions were more widely known.

78. Socolow, Robert H., 2007: Invited Foreword: CCS Technology: Ready to Go. Fundamentals of Carbon Capture and Storage Technology, The Petroleum Economist Ltd, Playhouse Yard, London, http://clients.digipage.co.uk/?userpath=00000049/00008053/00025360/&page=7, (ISBN: 1 86186 277 6), 4-9
    [ Abstract ]

    The heightened concern for climate change and the greater competitiveness of coal are on a collision course. To have a material effect, many hundreds of projects will be necessary.

79. Yang, C.-J., and Michael Oppenheimer, 2007: A “Manhattan Project” for Climate Change? Climatic Change, 80(3-4), doi:10.1007/S10584-006-9202-7 199-204
    [ Abstract ]

    Climate change is a chronic yet unprecedented threat to civilization. Large scale abatement of greenhouse-gas emissions would require not only replacing carbon-intensive fuels (like coal and oil) with low-emission or carbon-free energy alternatives, but also replacing much of the infrastructure that uses primary and secondary energy. As a political issue, the scale of the problem makes carbon mitigation unique and difficult to resolve. Its chronic nature is another obstacle to implementation of policy in the near term. It would take decades to displace fossil fuels even if the technologies to do so were available. Furthermore, disagreement has arisen on whether currently available technologies are sufficient to significantly reduce emissions over the next several decades (Pacala and Socolow 2004; Hoffert et al. 2002). The notion of developing new technologies before mandating emissions reductions has gained currency in response to these complexities. The Bush Administration climate policy favors this line of thinking, rejecting any Kyoto-style arrangement involving mandatory targets and proposing the development of new technologies as an alternative (Bush 2005). Here we argue that such approaches are based on the misconception that innovations needed for carbon mitigation can be effectively and efficiently developed without carbon regulations.

80. Budescu, D. V., R. Lempert, S. Broomell, and Klaus Keller, 2006: Aided and unaided decision making with imprecise probabilities. , http://www.geosc.psu.edu/~kkeller/Budescu_jep_09.pdf,
    [ Abstract ]

    We report results of a series of experiments on decision-making in the presence of irreducibly imprecise probabilities. The choices faced by the subjects resemble loosely the policy choices faced by policy makers in the presence of the threat of abrupt climate change. Consistent with the vagueness avoidance hypothesis, subjects displayed systematic preferences for riskless actions even at a high premium. This tendency increased as a function of the level of vagueness, characterized by the width of an interval of plausible probabilities. The vagueness avoidance tendency was reduced significantly when the subjects had access to one of two different decisions aids with distinct approaches to imprecision. The “Summary” aid provides quantitative comparisons of expected values of alternative actions while the “Display” aid graphically compares the performance of actions over the entire range of plausible probabilities. Although the decisions made in the presence of the two decisions aids were very similar in most respects, we found evidence for an interaction between the presentation format (operationalized by the type of decision aid used) and the subsequent decisions. Exposure to the graphical displays caused more subjects to favor the action that was perceived as superior for larger portions of the probability range, compared to subjects who had access to an expected value calculator. These findings suggest some initial implications for the debate over how to best characterize imprecise probabilistic information for policy-makers involved with climate change.

81. Crevoisier, C., M. N. Gloor, E. Gloaguen, L. W. Horowitz, Jorge Sarmiento, C. Sweeney, and P. P. Tans, 2006: A direct carbon budgeting approach to infer carbon sources and sinks. Design and synthetic application to complement the NACP observation network. Tellus, 58(5), doi:10.1111/j.1600-0889.2006.00214.x 366-375
    [ Abstract ]

    In order to exploit the upcoming regular measurements of vertical carbon dioxide (CO₂) profiles over North America implemented in the framework of the North American Carbon Program (NACP), we design a direct carbon budgeting approach to infer carbon sources and sinks over the continent using model simulations. Direct budgeting puts a control volume on top of North America, balances air mass in- and outflows into the volume and solves for the surface fluxes. The flows are derived from the observations through a geostatistical interpolation technique called Kriging combined with transport fields from weather analysis. The use of CO₂ vertical profiles simulated by the atmospheric transport model MOZART-2 at the planned 19 stations of the NACP network has given an estimation of the error of 0.39 GtC yr^-1 within the model world. Reducing this error may be achieved through a better estimation of mass fluxes associated with convective processes affecting North America. Complementary stations in the north-west and the north-east are also needed to resolve the variability of CO₂ in these regions. For instance, the addition of a single station near 52°N; 110°W is shown to decrease the estimation error to 0.34 GtC yr^-1.

82. De Lorenzo, L., and Robert H. Socolow, June 2006: Modeling Technology Choice under Alternative CO₂ Policies. Proceedings of the 8th International Conference on Greenhouse Gas Control Technologies (GHGT-8),
    [ Abstract ]

    Our work addresses the interaction between CO₂ policy and coal technology over the next 25 years. Coal power is a particularly attractive sector from which to seek CO₂ emission reductions because the emissions are from large point sources and several strategies are available to lower emissions. The electric industry currently contributes approximately 40% of global CO₂ emissions, and the coal electric industry about 30% of global CO₂ emissions. We develop a linear programming formalism that allows a high-level analysis of three kinds of competition: 1) between several kinds of new coal plants with and without CO₂ capture, each becoming more efficient and cheaper over time; 2) between retiring old coal plants, retrofitting them and constructing new ones; and 3) between building CO₂ capture capability into a new coal plant in two stages (the first stage being a “capture-ready” plant) and building the capability all at once. These competitions are examined under three matched pairs of trajectories of the CO₂ tax that result in three tax levels in 2030 ($100/tC, $200/tC and $300/tC): “sudden-change,” where the tax is increased suddenly at around 2020, and “gradual-change,” where the tax is increased gradually from 2005 to 2030 (fig.1). We find that: i) a “sudden-change” carbon tax induces more retrofitting of vintage plants than a policy with “gradual-change”; ii) all retrofit options considered appear at least once in the scenarios explored; iii) the case for capture-ready plants is weak with current cost numbers available from literature.

83. Greenblatt, J. B., Robert H. Socolow, and K. Riahi, June 2006: Wedge decomposition analysis: Application to SRES and Post-SRES Scenarios. Proceedings of the 8th International Conference on Greenhouse Gas Control Technologies (GHGT-8),
    [ Abstract ]

    We introduce a general methodology for displaying the gross assumptions behind any carbon emissions trajectory, relative to a reference trajectory, and we apply this methodology to a limited number of IPCC SRES scenarios [1]. These scenarios have been used widely for climate change analysis. We examine four scenarios (A1B, A2, B1, B2) together with three paired "post-SRES" scenarios [2, 3] that achieve CO₂ stabilization at 550 ppm by 2100. Our analysis is guided by the concept of the "stabilization wedge" introduced in a recent paper by Pacala and Socolow [4], which measures the quantitative contributions of specific technologies and strategies over the next 50 years in units of 1 GtC/yr reductions in 2050. We find that autonomous carbon-emissions reduction activity in the SRES scenarios account for a large number of "virtual" wedges, ranging from 8 to 35 in 2050. Roughly half of the virtual wedges in each scenario is due to energy efficiency improvements and structural change in the economy; most of the remaining half is due to high penetrations of non-fossil energy technologies. Post-SRES scenarios require only 2 to 4 "real" wedges in 2050, accounted for largely by greater non-fossil energy, greater energy efficiency, and CO₂ sequestration. Our results reveal that the SRES and post-SRES scenarios share a number of common assumptions. In particular we find that the baseline development path, i.e., the number of virtual wedges and "autonomous" trends in absence of any climate policies, play a central role in determining the mitigation effort needed for achieving climate stabilization.

84. Hawkins, D. G., D. A. Lashof, and Robert H. Williams, 2006: What to do about coal. , http://www.scientificamerican.com/article.cfm?id=what-to-do-about-coal-2006, 295(3), 68-75
    [ Abstract ]

    1. Coal is widely burned for power but produces large quantities of climate changing carbon dioxide.
    2. Compared with conventional power plants, new gasification facilities can more effectively and affordably extract CO₂ so it can be safely stored underground.
    3. The world must begin implementing carbon capture and storage soon to stave off global warming.

85. Kunkel, C., R. Hallberg, and Michael Oppenheimer, 2006: Coral Reefs Reduce Tsunami Impact in Model Simulations. Geophysical Research Letters, 33(L23612), doi:10.1029/2006GL027892
    [ Abstract ]

    Significant buffering of the impact of tsunamis by coral reefs is suggested by limited observations and some anecdotal reports, particularly following the 2004 Indian Ocean tsunami. Here we simulate tsunami run-up on idealized topographies in one and two dimensions using a nonlinear shallow water model and show that a sufficiently wide barrier reef within a meter or two of the surface reduces run-up on land on the order of 50%. We studied topographies representative of volcanic islands (islands with no continental shelf) but our conclusions may pertain to other topographies. Effectiveness depends on the amplitude and wavelength of the incident tsunami, as well as the geometry and health of the reef and the offshore distance of the reef. Reducing the threat to reefs from anthropogenic nutrients, sedimentation, fishing practices, channelbuilding, and global warming would help to protect some islands against tsunamis.

86. Larson, Eric, Robert H. Williams, and H. Jin, June 2006: Fuels and electricity from biomass with CO₂ capture and storage. Proceedings of the 8th International Conference on Greenhouse Gas Control Technologies (GHGT-8), Trondheim, Norway, http://www.princeton.edu/pei/energy/publications/texts/IK-Larson-et-al-GHGT8-FI,
    [ Abstract ]

    Mass/energy balances and financial analysis are presented for (1) plants co-producing Fischer- Tropsch diesel and gasoline blendstocks plus electricity from biomass and (2) biomass integrated gasification combined cycle power plants. Plant designs with and without carbon capture and storage are analyzed. The feedstock is switchgrass. For plants with CO₂ capture, we assume that the CO₂ is stored in deep saline aquifers or used for enhanced oil recovery.

87. Naik, V., D. L. Mauzerall, L. W. Horowitz, M. D. Schwarzkopf, V. Ramaswamy, and Michael Oppenheimer, 2006: Net radiative forcing due to changes in regional emissions of tropospheric ozone precursors. Journal of Geophysical Research, 110(D24306), doi:10.1029/2005JD005908
    [ Abstract ]

    The global distribution of tropospheric ozone (O₃) depends on the emission of precursors, chemistry, and transport. For small perturbations to emissions, the global radiative forcing resulting from changes in O₃ can be expressed as a sum of forcings from emission changes in different regions. Tropospheric O₃ is considered in present climate policies only through the inclusion of indirect effect of CH₄ on radiative forcing through its impact on O₃ concentrations. The short-lived O₃ precursors (NO_x, CO, and NMHCs) are not directly included in the Kyoto Protocol or any similar climate mitigation agreement. In this study, we quantify the global radiative forcing resulting from a marginal reduction (10%) in anthropogenic emissions of NO_x alone from nine geographic regions and a combined marginal reduction in NO_x, CO, and NMHCs emissions from three regions. We simulate, using the global chemistry transport model MOZART-2, the change in the distribution of global O₃ resulting from these emission reductions. In addition to the short-term reduction in O₃, these emission reductions also increase CH₄ concentrations (by decreasing OH); this increase in CH₄ in turn counteracts part of the initial reduction in O₃ concentrations. We calculate the global radiative forcing resulting from the regional emission reductions, accounting for changes in both O₃ and CH₄. Our results show that changes in O₃ production and resulting distribution depend strongly on the geographical location of the reduction in precursor emissions. We find that the global O₃ distribution and radiative forcing are most sensitive to changes in precursor emissions from tropical regions and least sensitive to changes from midlatitude and high-latitude regions. Changes in CH₄ and O₃ concentrations resulting from NO_x emission reductions alone produce offsetting changes in radiative forcing, leaving a small positive residual forcing (warming) for all regions. In contrast, for combined reductions of anthropogenic emissions of NO_x, CO, and NMHCs, changes in O₃ and CH₄ concentrations result in a net negative radiative forcing (cooling). Thus we conclude that simultaneous reductions of CO, NMHCs, and NO_x lead to a net reduction in radiative forcing due to resulting changes in tropospheric O₃ and CH₄ while reductions in NO_x emissions alone do not.

88. Nævdal, E., 2006: Dynamic Optimisation in the Presence of Threshold Effects when the Location of the Threshold is Uncertain - With an Application to a Possible Disintegration of the Western Antarctic Ice Sheet. Journal of Economic Dynamics and Control, 30(7), doi:10.1016/j.jedc.2005.04.004 1131-1158
    [ Abstract ]

    The purpose of this paper is to derive necessary conditions for optimal control in the presence of threshold effects when the threshold is a curve in n-dimensional space of uncertain location. The usefulness of these conditions is shown by examining the optimal regulation of two greenhouse gases when there is a risk that the combined radiative forcing from these two gases may trigger the disintegration of the Western Antarctic ice sheet.

89. O'Neill, B., P. Crutzen, A. Grübler, M. H. Duong, Klaus Keller, C. Kolstad, A. Lange, M. Obersteiner, Michael Oppenheimer, W. Pepper, W. Sanderson, and M. Schlesinger, et al., 2006: Learning and Climate Change. Climate Policy, http://www.geosc.psu.edu/~kkeller/O%27Neill_cp_07.pdf, 6,
    [ Abstract ]

    Learning – i.e. the acquisition of new information that leads to changes in our assessment of uncertainty – plays a prominent role in the international climate policy debate. For example, the view that we should postpone actions until we know more continues to be influential. The latest work on learning and climate change includes new theoretical models, better informed simulations of how learning affects the optimal timing of emissions reductions, analyses of how new information could affect the prospects for reaching and maintaining political agreements and for adapting to climate change, and explorations of how learning could lead us astray rather than closer to the truth. Despite the diversity of this new work, a clear consensus on a central point is that the prospect of learning does not support the postponement of emissions reductions today.

90. Oppenheimer, Michael, 2006: Science and Environmental Policy: The Role of Nongovernmental Organizations. Social Research, http://findarticles.com/p/articles/mi_m2267/is_3_73/ai_n27052540/,
    [ Abstract ]

    THIS PAPER ADDRESSES THE ROLE OF NONGOVERNMENTAL ORGANIZATIONS, or NGOs, in the science-policy nexus. I shall draw on my 21 years of experience working for a nongovernmental organization, Environmental Defense, my earlier experience as a research scientist, and my recent experience as a professor, the latter two positions at large universities. I hope this quasi-anecdotal approach is informative, but in addition, it is a necessity because there have been relatively few academic studies of nongovernmental advocacy organizations.

91. Socolow, Robert H., and Stephen W. Pacala, 2006: A Plan to Keep Carbon in Check. Scientific American, http://www.scientificamerican.com/carbon/0906050.pdf, 295(3), 50-57
    [ Abstract ]

    Humanity can emit only so much carbon dioxide into the atmosphere before the climate enters a state unknown in recent geologic history and goes haywire. Climate scientists typically see the risks growing rapidly as CO₂ levels approach a doubling of their pre-18thcentury value. To make the problem manageable, the required reduction in emissions can be broken down into “wedges”—an incremental reduction of a size that matches available technology.

92. Socolow, Robert H., 2006: Stabilization Wedges: An Elaboration of the Concept. Avoiding Dangerous Climate Change, Schellnhuber, H.J., et al., eds., Cambridge University Press, Cambridge, MA, http://homepage.mac.com/marty.hoffert/filechute/SocolowRedux.pdf, Chapter 36, 347-354
    [ Abstract ]

    We have earlier introduced the stabilization wedge as a useful unit for discussing climate stabilization. A wedge is 1GtC/yr or emissions savings in 2055, achieved by a single strategy that will not occur without deliberate attention to global carbon. Implementing seven wedges should place humanity, approximately, on a path to stabilizing the climate at a concentration less than double the pre-industrial concentration, leaving those at the helm in the following 50 years in a position to drive CO₂ emissions to net zero emissions; arguably, the tasks of the two half-centuries are comparably difficult. We elaborate on the concept of the stabilization wedge that is achieved through carbon policy by introducing the "virtual" wedge that is achieved as a result of the continued decarbonization of the global economy even in the absence of carbon policy. Virtual wedges are already embedded in almost all "baseline" scenarios, because the decarbonization of the global economy is a robust historical trend. Thus, the stabilization wedges must be achieved over and above the structural shifts, evergy efficiency gains, and energy system decarbonization that are likely to occur in the next 50 years even without carbon policy. We discuss stabilization wedges of energy efficiency, calling attention to the importance of avoiding investments in durable capital facilities, like power plants and apartment buildings, that are energy-inefficient or carbon-wasteful. We briefly explore wedges of capture and storage, nuclear energy, and renewable energy. The wedges framework highlights the importance of early involvement of the developing countries in mitigation activity. The wedges framework, therefore, may be able to contribute new elements to global carbon policy, by aligning the concept of differentiated responsibilities across countries with a global commitment to the internationally coordinated commercialization of low-carbon technology.

93. Socolow, Robert H., et al., June 2006: Tributes to Amulya Reddy. Energy for Sustainable Development, 10(2), doi:10.1016/S0973-0826(08)60526-8 15
    [ Abstract ]

    With Amulya Reddy’s passing we have lost a dear friend and colleague. In our collaboration that came to be known as “The Gang of Four” and spanned nearly three decades, we learned much from each other that we were able to transform into a global strategy to put energy on a track that promotes sustainable development. Amulya will continue to live on in our hearts and minds as a result of this collectively evolved strategy that would be very incomplete without Amulya’s imprint. Though others know much more about the impacts of his activities at the local, state, and national levels in India, we would like to share with colleagues a history of our collaboration that highlights Amulya’s legacy at the international level.

94. Succar, Samir, J. B. Greenblatt, D. C. Denkenberger, and Robert H. Williams, 2006: An Integrated Optimization Of Large-Scale Wind With Variable Rating Coupled To Compressed Air Energy Storage. Proceedings of the AWEA Windpower 2006, Pittsburgh, PA, http://www.princeton.edu/~ssuccar/recent/Succar_AWEAPaper_June06.pdf,
    [ Abstract ]

    A methodology is presented for jointly optimizing the wind turbine specific rating and the storage configuration for a large-scale wind farm coupled to compressed air energy storage (CAES). By allowing the wind-storage system to be optimized in an integrated, variable rating framework the overall cost of energy (COE) can be reduced substantially. These changes also enhance the capacity factor of the wind array, reduce the storage capacity requirements of the baseload plant and reduce the greenhouse gas emission rate of the overall system relative to a separately optimized wind farm couple to CAES. The results of this analysis could have important implications for th ecompetitiveness of large-scale remote wind and the applicability of energy storage as a baseload wind strategy in a carbon constrained world.

95. Succar, Samir, J. B. Greenblatt, and Robert H. Williams, May 2006: Comparing Coal IGCC with CCS and Wind-CAES Baseload Power Options in a Carbon-Constrained World. Proceedings of the Fifth Annual Conference on Carbon Capture & Sequestration, Alexandria, Virginia, http://www.princeton.edu/~ssuccar/recent/Succar_NETLPaper_May06.pdf,
    [ Abstract ]

    Coal integrated gasification combined cycle (IGCC) with carbon capture and storage (CCS) has emerged as a potentially cost-effective carbon mitigation strategy. However carbon policies that make energy systems such as IGCC with CCS competitive with conventional fossil power generators will also bring other low carbon technologies into play. In particular, two strategies for generating baseload power from wind are investigated: pairing wind with dedicated natural gas generation and coupling wind energy to compressed air energy storage (CAES). The costs and performance of these options are analyzed in comparison to coal IGCC with and without CCS. We find that wind with natural gas backup faces significant challenges in economic dispatch competition due to high fuel prices. However CAES, a commercially ready technology, makes it possible to transform wind power into a baseload power option with the low short-run marginal cost needed to compete in baseload markets. Moreover, geologies suitable for CAES seem to be reasonably well distributed in wind-rich regions of the United States (e.g., Great Plains) where much of the new capacity for coal power generation is being planned. An economic analysis indicates that costs and greenhouse gas emission levels of wind-CAES systems fired with natural gas will be comparable to those of coal IGCC with CCS, and could be strong competitors for coal IGCC with CCS in providing baseload electricity in a carbon-constrained world.

96. Succar, Samir, J. B. Greenblatt, and Robert H. Williams, April 2006: Arguing the case for storage. Windpower Monthly, 22(4), 8-10
    [ Abstract ]

    Whether or not storage is needed depends on the aspirations for wind power. Although there is a large potential for wind power expansion in serving non-base load markets, this should be regarded as a near term opportunity for expanding wind generation from its current very small base production level. If wind energy is to become a truly large player in electricity markets globally it must be able to compete with base load power, which accounts for most electricity generation. Notably, 70% of US electricity and 60% of global electricity are currently provided by coal and nuclear power, mostly via base load power plants.

97. Tol, R.S.J., and David F. Bradford, 2006: The Polluter Pays Principle and Cost-Benefit Analysis of Climate Change: An Application of FUND. Working Papers FNU-98, http://ideas.repec.org/p/sgc/wpaper/98.html
    [ Abstract ]

    I compare and contrast five climate scenarios: (1) no climate policy; (2) non-cooperative cost-benefit analysis (NC CBA); (3) NC CBA with international permit trade; (4) NC CBA with joint and several liability for climate change damages; and (5) NC CBA with liability proportional to a country’s share in cumulative emissions. As estimates of the marginal damage costs are low, standard NC CBA implies only limited emission abatement. With international permit trade, emission abatement is even less, as the carbon tax is reduced in countries with fast-growing emissions, and because a permit market ignores the positive, dynamic externalities of abatement. Proportional liability shifts abatement effort towards the richer countries, but away from the fast-growing economies; again, long-term, global emission abatement is reduced. Joint and several liability would lead to more stringent climate policy. These findings are qualitatively robust to the size and accounting of climate change impacts, to the definition of liability, and to the baseline scenario.

98. Tol, R.S.J., Robert H. Socolow, and Stephen W. Pacala, 2006: Understanding Long-Term Energy Use and Carbon Dioxide Emissions in the USA. Fondazione Eni Enrico Mattei Working Papers, doi:10.1016/j.jpolmod.2008.12.002
    [ Abstract ]

    We compile a database of energy uses, energy sources, and carbon dioxide emissions for the USA for the period 1850-2002. We use a model to extrapolate the missing observations on energy use by sector. Overall emission intensity rose between 1850 and 1917, and fell between 1917 and 2002. The leading cause for the rise in emission intensity was the switch from wood to coal, but population growth, economic growth, and electrification contributed as well. After 1917, population growth, economic growth and electrification pushed emissions up further, and there was no net shift from fossil to non-fossil energy sources. From 1850 to 2002, emissions were reduced by technological and behavioural change (particularly in transport, manufacturing and households), structural change in the economy, and a shift from coal to oil and gas. These trends are stronger than electrification, explaining the fall in emissions relative to GDP.

99. Williams, Robert H., Eric Larson, and H. Jin, May 2006: Comparing climate - change mitigating potentials of alternative synthetic liquid fuel technologies using biomass and coal. Proceedings of the 5th Annual Conference on Carbon Capture and Sequestration, http://www.netl.doe.gov/publications/proceedings/06/carbon-seq/Tech%20Session%20178.pdf,
    [ Abstract ]

    The climate-change mitigation potentials of alternative options for making synthetic liquid fuel from coal and biomass without and with CO₂ capture and storage are explored. The emphasis is on making Fischer-Tropsch liquids, with comparisons to cellulosic ethanol. Particular attention is given to exploitation of the negative CO₂ emissions potential of CO₂ capture and storage for bioenergy systems. One Fischer-Tropsch option involves coprocessing biomass and coal. All liquid fuel production options involve production of electricity as a net coproduct. Both CO₂ aquifer storage and CO₂ enhanced oil recovery options are analyzed. The metrics by which the alternatives are compared are: (i) the net greenhouse gas emission rate associated with liquid fuel production and use, (ii) the specific capital cost of liquid fuel production, (iii) the lifecycle cost calculated for a fixed capital charge rate, and (iv) the internal rate of return on equity as a function of both the crude oil price and the price of greenhouse gas emissions. In addition, for options that involve biomass, liquid fuel yields per tonne of biomass are compared. And for enhanced oil recovery applications of the captured CO₂, the relative profitability of using CO₂ from synfuel plants and integrated gasifier combined cycle power plants is explored.

100. Williams, Robert H., Eric Larson, and H. Jin, June 2006: Synthetic fuels in a world with high oil and carbon prices. Proceedings of the 8th International Conference on Greenhouse Gas Control Technologies (GHGT-8), http://www.futurecoalfuels.org/documents/032007_williams.pdf,
     [ Abstract ]

     Four carbon management options are investigated for making Fischer-Tropsch fuels plus electricity: three processing coal and one co-processing coal and biomass. Energy and carbon balances are estimated. Economic analyses are carried out for carbon prices of $0 and $100 per tonne of carbon. Both levelized costs and internal rates of return on equity are estimated with CO₂ vented, and with CO₂ captured and stored in saline aquifers, and with CO₂ captured and used for enhanced oil recovery. Comparisons are made with coal integrated gasifier combined cycle power plants. When the carbon price is $100 per tonne of carbon, the co-processing option is the most economically attractive option for making Fischer-Tropsch liquids. Even at zero carbon price enhanced oil recovery applications of captured CO₂ will often be economically attractive where such opportunities exist. Enhanced oil recovery is a sufficiently large and economically interesting niche in the USA (and perhaps elsewhere) that it could enable wide near-term experience with gasification-based energy and carbon capture and storage technologies.

101. Chiesa, P., S. Consonni, Thomas Kreutz, and Robert H. Williams, 2005: Co-production of Hydrogen, Electricity, and CO₂ from Coal with Commercially Ready Technology. Part A: Performance and Emissions. International Journal of Hydrogen Energy, 30(7), doi:10.1016/j.ijhydene.2004.08.002 747-767
     [ Abstract ]

     This two-part paper investigates performances, costs and prospects of using commercially ready technology to convert coal to H₂ and electricity, with CO₂ capture and storage. Part A focuses on plant configuration and the evaluation of performances and CO₂ emissions. Part B focuses on economics, establishing benchmarks for the assessment of novel technologies and guidelines for technological development. In the co-production plants considered in the paper, coal is gasified to synthesis gas in an entrained flow gasifier. The syngas is cooled, cleaned of particulate matter, and shifted (to primarily H₂ and CO₂ in sour water–gas shift reactors. After further cooling, H₂S is removed from the syngas using a physical solvent (Selexol); CO₂ is then removed from the syngas, again using Selexol; after being stripped from the solvent, the CO₂ is dried and compressed to 150 bar for pipeline transport and underground storage. High purity H₂ (99.999%) is extracted from the H₂-rich syngas via a pressure swing adsorption (PSA) unit and delivered at 60 bar. The PSA purge gas is compressed and burned in a conventional gas turbine combined cycle, generating co-product electricity. The H₂/electricity ratio can be varied by lowering the steam-to-carbon ratio in the syngas or by letting part of the de-carbonized syngas by-pass the PSA unit. Performances and emissions of H₂/electricity co-production with CO₂ capture are compared with those of a system that vents the CO₂. We examine different methods of syngas heat recovery (quench versus radiant cooling) and explore the effects of changing the electricity/H₂ ratio, gasifier pressure and hydrogen purity. Results show that state-of-the-art commercial technology allows transferring to de-carbonized hydrogen 57–58% of coal LHV, while exporting to the grid decarbonized electricity amounting to 2–6% of coal LHV. In contrast to decarbonizing coal IGCC electricity, which entails a loss of 6–8 percentage points of electricity conversion when capturing CO₂ as an alternative to venting it, CO₂ capture for H₂ production gives a minor energy penalty (∼ 2 percentage points of export electricity). For H2 production, the efficiency gain achievable by hot syngas cooling vs. quench is a modest 2 percentage point increase in electricity for export, compared to 2–4 percentage points in the electricity case. Reducing H2 purity or increasing gasification pressure has minor effects on performance.

102. Donner, S. D., W. J. Skirving, C. M. Little, Michael Oppenheimer, and O. Hoegh-Guldberg, 2005: Global assessment of coral bleaching and required rates of adaptation under climate change. Global Change Biology, 11(12), doi:10.1111/j.1365-2486.2005.01073.x 2251-2265
     [ Abstract ]

     Elevated ocean temperatures can cause coral bleaching, the loss of colour from reefbuilding corals because of a breakdown of the symbiosis with the dinoflagellate Symbiodinium. Recent studies have warned that global climate change could increase the frequency of coral bleaching and threaten the long-term viability of coral reefs. These assertions are based on projecting the coarse output from atmosphere–ocean general circulation models (GCMs) to the local conditions around representative coral reefs. Here, we conduct the first comprehensive global assessment of coral bleaching under climate change by adapting the NOAA Coral ReefWatch bleaching prediction method to the output of a low- and high-climate sensitivity GCM. First, we develop and test algorithms for predicting mass coral bleaching with GCM-resolution sea surface temperatures for thousands of coral reefs, using a global coral reef map and 1985–2002 bleaching prediction data. We then use the algorithms to determine the frequency of coral bleaching and required thermal adaptation by corals and their endosymbionts under two different emissions scenarios. The results indicate that bleaching could become an annual or biannual event for the vast majority of the world’s coral reefs in the next 30–50 years without an increase in thermal tolerance of 0.2 – 1.0°C per decade. The geographic variability in required thermal adaptation found in each model and emissions scenario suggests that coral reefs in some regions, like Micronesia and western Polynesia, may be particularly vulnerable to climate change. Advances in modelling and monitoring will refine the forecast for individual reefs, but this assessment concludes that the global prognosis is unlikely to change without an accelerated effort to stabilize atmospheric greenhouse gas concentrations.

103. Duke, R., Robert H. Williams, and A. Payne, 2005: Accelerating residential PV expansion: demand analysis for competitive electricity markets. Energy Policy, 33(15), doi:10.1016/j.enpol.2004.03.005 1910-1929
     [ Abstract ]

     This article quantifies the potential market for grid-connected, residential photovoltaic (PV) electricity integrated into new homes built in the US. It complements an earlier supply-side analysis by the authors that demonstrates the potential to reduce PV module prices below $1.5/W^p by scaling up existing thin-film technology in 100MW^p/yr manufacturing facilities. The present article demonstrates that, at that price, PV modules may be cost effective in 125,000 new home installations per year (0.5GW^p/yr). While this market is large enough to support multiple scaled up thin-film PV factories, inefficient energy pricing and demand-side market failures will inhibit prospective PV consumers without strong public policy support. Net metering rules, already implemented in many states to encourage PV market launch, represent a crude but reasonable surrogate for efficient electricity pricing mechanisms that may ultimately emerge to internalize the externality benefits of PV. These public benefits include reduced air pollution damages (estimated costs of damage to human health from fossil fuel power plants are presented in Appendix A), deferral of transmission and distribution capital expenditures, reduced exposure to fossil fuel price risks, and increased electricity system reliability for end users. Thus, net metering for PV ought to be implemented as broadly as possible and sustained until efficient pricing is in place. Complementary PV ‘‘buydowns’’ (e.g., a renewable portfolio standard with a specific PV requirement) are needed to jumpstart regional PV markets.

104. Fiore, A. M., L. W. Horowitz, D. W. Purves, H. Levy II, M. J. Evans, Y. Wang, Y. Li, and R. M. Yantosca, 2005: Evaluating the contribution of changes in isoprene emissions to surface ozone trends over the eastern United States. Journal of Geophysical Research, 110(D12303), doi:10.1029/2004JD005485
     [ Abstract ]

     Reducing surface ozone (O₃) to concentrations in compliance with the national air quality standard has proven to be challenging, despite tighter controls on O₃ precursor emissions over the past few decades. New evidence indicates that isoprene emissions changed considerably from the mid-1980s to the mid-1990s owing to land-use changes in the eastern United States (Purves et al., 2004). Over this period, U.S. anthropogenic VOC (AVOC) emissions decreased substantially. Here we apply two chemical transport models (GEOS-CHEM and MOZART-2) to test the hypothesis, put forth by Purves et al. (2004), that the absence of decreasing O₃ trends over much of the eastern United States may reflect a balance between increases in isoprene emissions and decreases in AVOC emissions. We find little evidence for this hypothesis; over most of the domain, mean July afternoon (1300–1700 local time) surface O₃ is more responsive (ranging from -9 to +7 ppbv) to the reported changes in anthropogenic NO_x emissions than to the concurrent isoprene (-2 to +2 ppbv) or AVOC (-2 to 0 ppbv) emission changes. The estimated magnitude of the O₃ response to anthropogenic NO_x emission changes, however, depends on the base isoprene emission inventory used in the model. The combined effect of the reported changes in eastern U.S. anthropogenic plus biogenic emissions is insufficient to explain observed changes in mean July afternoon surface O₃ concentrations, suggesting a possible role for decadal changes in meteorology, hemispheric background O₃, or subgrid-scale chemistry. We demonstrate that two major uncertainties, the base isoprene emission inventory and the fate of isoprene nitrates (which influence surface O₃ in the model by -15 to +4 and +4 to +12 ppbv, respectively), preclude a well-constrained quantification of the present-day contribution of biogenic or anthropogenic emissions to surface O₃ concentrations, particularly in the high-isopreneemitting southeastern United States. Better constraints on isoprene emissions and chemistry are needed to quantitatively address the role of isoprene in eastern U.S. air quality.

105. Gale, J., J. Bradshaw, Z. Chen, A. Garg, D. Gomez, H. H. Rogner, D. Simbeck, Robert H. Williams, F. Toth, and D. van Vuuren, 2005: Sources of CO₂, Chapter 2 in Carbon Dioxide Capture and Storage. Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, MA, http://www.ipcc.ch/pdf/special-reports/srccs/srccs_chapter2.pdf,
     [ Abstract ]

     Assessing CO₂ capture and storage calls for a comprehensive delineation of CO₂ sources. The attractiveness of a particular CO₂ source for capture depends on its volume, concentration and partial pressure, integrated system aspects, and its proximity to a suitable reservoir. Emissions of CO₂ arise from a number of sources, mainly fossil fuel combustion in the power generation, industrial, residential and transport sectors. In the power generation and industrial sectors, many sources have large emission volumes that make them amenable to the addition of CO₂ capture technology. Large numbers of small point sources and, in the case of transport, mobile sources characterize the other sectors, making them less amenable for capture at present. Technological changes in the production and nature of transport fuels, however, may eventually allow the capture of CO₂ from energy use in this sector.
     Over 7,500 large CO₂ emission sources (above 0.1 MtCO₂ yr-1) have been identified. These sources are distributed geographically around the world but four clusters of emissions can be observed: in North America (the Midwest and the eastern freeboard of the USA), North West Europe, South East Asia (eastern coast) and Southern Asia (the Indian sub-continent). Projections for the future (up to 2050) indicate that the number of emission sources from the power and industry sectors is likely to increase, predominantly in Southern and South East Asia, while the number of emission sources suitable for capture and storage in regions like Europe may decrease slightly.
     Comparing the geographical distribution of the emission sources with geological storage opportunities, it can be seen that there is a good match between sources and opportunities. A substantial proportion of the emission sources are either on top of, or within 300 km from, a site with potential for geological storage. Detailed studies are, however, needed to confirm the suitability of such sites for CO₂ storage. In the case of ocean storage, related research suggests that only a small proportion of large emission sources will be close to potential ocean storage sites.
     The majority of the emissions sources have concentrations of CO₂ that are typically lower than 15%. However, a small proportion (less than 2%) have concentrations that exceed 95%, making them more suitable for CO₂ capture. The high content sources open up the possibility of lower capture costs compared to low-content sources because only dehydration and compression are required. The future proportion of highand low-content CO₂ sources will largely depend on the rate of introduction of hydrogen, biofuels, and the gasification or liquefaction of fossil fuels, as well as future developments in plant sizes.
     Technological changes, such as the centralized production of liquid or gaseous energy carriers (e.g., methanol, ethanol or hydrogen) from fossil sources or the centralized production of those energy carriers or electricity from biomass, may allow for CO₂ capture and storage. Under these conditions, power generation and industrial emission sources would largely remain unaffected but CO₂ emissions from transport and distributed energy-supply systems would be replaced by additional point sources that would be amenable to capture. The CO₂ could then be stored either in geological formations or in the oceans. Given the scarcity of data, it is not possible to project the likely numbers of such additional point sources, or their geographical distribution, with confidence (estimates range from 0 to 1,400 GtCO₂ (0–380 GtC) for 2050).
     According to six illustrative SRES scenarios, global CO₂ emissions could range from 29.3 to 44.2 GtCO₂ (8–12 GtC) in 2020 and from 22.5 to 83.7 GtCO₂ (6–23 GtC) in 2050. The technical potential of CO₂ capture associated with these emission ranges has been estimated recently at 2.6–4.9 GtCO₂ for 2020 (0.7–1.3 GtC) and 4.9– 37.5 GtCO₂ for 2050 (1.3–10 GtC). These emission and capture ranges reflect the inherent uncertainties of scenario and modelling analyses. However, there is one trend common to all of the six illustrative SRES scenarios: the general increase of future CO₂ emissions in the developing countries relative to the industrialized countries.

106. Gruner, Sol M., Pierre A. Piroue, and Robert H. Socolow, October 2005: George T. Reynolds (an obituary). Physics Today, http://www.physicstoday.org,
107. Keller, Klaus, M. G. Hall, S.-R. Kim, David F. Bradford, and Michael Oppenheimer, 2005: Avoiding dangerous anthropogenic interference with the climate system. Climatic Change, 73(3), doi:10.1007/s10584-005-0426-8 227-238
     [ Abstract ]

     The UN Framework Convention on Climate Change calls for the avoidance of “dangerous anthropogenic interference with the climate system”. Among the many plausible choices, dangerous interference with the climate system may be interpreted as anthropogenic radiative forcing causing distinct and widespread climate change impacts such as a widespread demise of coral reefs or a disintegration of the West Antarctic ice sheet. The geological record and numerical models suggest that limiting global warming below critical temperature thresholds significantly reduces the likelihood of these eventualities. Here we analyze economically optimal policies that may ensure this risk-reduction. Reducing the risk of a widespread coral reef demise implies drastic reductions in greenhouse gas emissions within decades. Virtually unchecked greenhouse gas emissions to date (combined with the inertia of the coupled natural and human systems) may have already committed future societies to a widespread demise of coral reefs. Policies to reduce the risk of a West Antarctic ice sheet disintegration allow for a smoother decarbonization of the economy within a century and may well increase consumption in the long run.

108. Kreutz, Thomas, Robert H. Williams, S. Consonni, and P. Chiesa, 2005: Co-production of Hydrogen, Electricity, and CO₂ from Coal with Commercially Ready Technology. Part B: Economic Analysis. International Journal of Hydrogen Energy, 30(7), doi:10.1016/j.ijhydene.2004.08.001 769-784
     [ Abstract ]

     This two-part paper investigates performances, costs and prospects of using commercially ready technology to convert coal to H₂ and electricity, with CO₂ capture and storage. Part A focuses on plant configuration, performance, and CO₂ emissions. Part B focuses on the cost of producing H₂ and electricity, with and without reduced CO₂ emissions. Our estimates show that the costs for ∼ 91% decarbonized energy (via quench gasification at 70 bar) are about 6.2 ¢/kWh for electricity and about $ 1.0/kg (8.5 $/GJ, LHV) for hydrogen; these are, respectively, 35% and 19% higher than the corresponding energy costs with CO₂ venting. Referenced to these analogous CO₂ venting plants, the costs of CO₂ emissions avoided are ∼ 24 $/tonne for electricity and 11 $/tonne for H₂.

109. Mauzerall, D. L., B. Sultan, N. Kim, and David F. Bradford, 2005: NO_x EmissionsFrom Large Point Sources: Variability in Ozone Production, Resulting Health Dangers and Economic Costs. Atmospheric Environment, 39(16), doi:10.1016/j.atmosenv.2004.12.041 2851-2866
     [ Abstract ]

     Several models predict large and potentially abrupt ocean circulation changes due to anthropogenic greenhouse-gas emissions. These circulation changes drive-in the models-considerable oceanic oxygen trend. A sound estimate of the observed oxygen trends can hence be a powerful tool to constrain predictions of future changes in oceanic deepwater formation, heat and carbon dioxide uptake. Estimating decadal scale oxygen trends is, however, a nontrivial task and previous studies have come to contradicting conclusions. One key potential problem is that changes in the historical observation network might introduce considerable errors. Here we estimate the likely magnitude of these errors for a subset of the available observations in the Southern Ocean. We test three common data analysis methods south of Australia and focus on the decadal-scale trends between the 1970’s and the 1990’s. Specifically, we estimate errors due to sparsely sampled observations using a known signal (the time invariant, temporally averaged, World Ocean Atlas 2001) as a negative control. The crossover analysis and the objective analysis methods are far less prone to spatial sampling location biases than the area averaging method. Subject to numerous caveats, we find that errors due to sparse sampling for the area averaging method are on the order of several micromoles kg^-1. For the crossover and the objective analysis method, these errors are much smaller. For the analyzed example, the biases due to changes in the spatial design of the historical observation network are relatively small compared to the trends predicted by many model simulations. This raises the possibility to use historic oxygen trends to constrain model simulations, even in sparsely sampled ocean basins.

110. Min, D.-H., and Klaus Keller, 2005: Errors in estimated temporal tracer trends due to changes in the historical observation network: A case study of oxygen trends in the Southern Ocean. Ocean and Polar Research, http://www.geosc.psu.edu/~kkeller/Min_and_Keller_opr_05.pdf, 27(2), 189-195
     [ Abstract ]

     Several models predict large and potentially abrupt ocean circulation changes due to anthropogenic greenhouse-gas emissions. These circulation changes drive-in the models-considerable oceanic oxygen trend. A sound estimate of the observed oxygen trends can hence be a powerful tool to constrain predictions of future changes in oceanic deepwater formation, heat and carbon dioxide uptake. Estimating decadal scale oxygen trends is, however, a nontrivial task and previous studies have come to contradicting conclusions. One key potential problem is that changes in the historical observation network might introduce considerable errors. Here we estimate the likely magnitude of these errors for a subset of the available observations in the Southern Ocean. We test three common data analysis methods south of Australia and focus on the decadal-scale trends between the 1970’s and the 1990’s. Specifically, we estimate errors due to sparsely sampled observations using a known signal (the time invariant, temporally averaged, World Ocean Atlas 2001) as a negative control. The crossover analysis and the objective analysis methods are far less prone to spatial sampling location biases than the area averaging method. Subject to numerous caveats, we find that errors due to sparse sampling for the area averaging method are on the order of several micromoles kg⁻¹. For the crossover and the objective analysis method, these errors are much smaller. For the analyzed example, the biases due to changes in the spatial design of the historical observation network are relatively small compared to the trends predicted by many model simulations. This raises the possibility to use historic oxygen trends to constrain model simulations, even in sparsely sampled ocean basins.

111. Ming, Y., L. M. Russell, and David F. Bradford, 2005: Health and Climate Policy Impacts on Sulfur Emissions Control. Geophysical Review, 43(R6400), doi:10.1029/2004RG000167
     [ Abstract ]

     Sulfate aerosol from burning fossil fuels not only has strong cooling effects on the Earth’s climate but also imposes substantial costs on human health. To assess the impact of addressing air pollution on climate policy, we incorporate both the climate and health effects of sulfate aerosol into an integrated-assessment model of fossil fuel emission control. Our simulations show that a policy that adjusts fossil fuel and sulfur emissions to address both warming and health simultaneously will support more stringent fossil fuel and sulfur controls. The combination of both climate and health objectives leads to an acceleration of global warming in the 21st century as a result of the short-term climate response to the decreased cooling from the immediate removal of short-lived sulfate aerosol. In the long term (more than 100 years), reducing sulfate aerosol emissions requires that we decrease fossil fuel combustion in general, thereby removing some of the coemitted carbon emissions and leading to a reduction in global warming.

112. Oppenheimer, Michael, and A. Petsonk, 2005: Article 2 of the UNFCCC: Historical Origins, Recent Interpretations. Climatic Change, 73(3), doi:10.1007/s10584-005-0434-8 195-226
     [ Abstract ]

     Article 2 of the UN Framework Convention on Climate Change (UNFCCC), which states the treaty’s long-term objective, is the subject of a growing literature that examines means to interpret and implement this provision. Here we provide context for these studies by exploring the intertwined scientific, legal, economic, and political history of Article 2. We review proposed definitions for “dangerous anthropogenic interference” and frameworks that have been proposed for implementing these definitions. Specific examples of dangerous climate changes suggest limits on global warming ranging from 1 to 4°C and on concentrations ranging from 450 to 700 ppm CO₂ equivalents. The implications of Article 2 for near term restrictions on greenhouse-gas emissions, e.g., the Kyoto Protocol, are also discussed.

113. Oppenheimer, Michael, and R. B. Alley, 2005: Ice Sheets, Global Warming, and Article 2 of the UNFCCC. Climatic Change, 68(3), doi:10.1007/s10584-005-5372-y 257-267
     [ Abstract ]

     Rapid disintegration of the West Antarctic ice sheet (WAIS) was cited decades ago as a potentially severe consequence of global warming (Mercer, 1968, 1978; Revelle, 1983) and climate scientists have cast a wary eye toward the cryosphere ever since. Total loss of the West Antarctic or Greenland ice sheet (GIS) would cause eustatic sea level rise of 4–6 m and 7 m, respectively. The stability of the much larger East Antarctic ice sheet (EAIS) is sometimes questioned but it is likely that the two other ice sheets would disintegrate with less warming. Initially, WAIS was the main focus of concern because as a marine ice sheet, it was thought by many to be inherently unstable (Oppenheimer, 1998). That WAIS has undergone a large reduction in area and perhaps in mass since the Last Glacial Maximum (Bindschadler, 1998; Huybrechts, 2002) provides evidence of its vulnerability to global temperature and sea level variations. In contrast, GIS is estimated to have shrunken by about 30% from its LGM volume (Fleming and Lambeck, 2004). Disintegration ofWAIS may provide a plausible example of “dangerous anthropogenic interference with the climate system” under Article 2 of theUNFramework Convention on Climate Change. In this context, two recent studies proposed specific temperatures and greenhouse gas concentrations (O’Neill and Oppenheimer, 2002, Oppenheimer and Alley, 2004) to be avoided. A key issue is the degree to which warming can affect the rate of ice loss by altering the mass balance between precipitation rates on the one hand, and melting and ice discharge to the ocean through ice streams on the other.

114. Oppenheimer, Michael, 2005: Defining Dangerous Anthropogenic Interference: The Role of Science, the Limits of Science. Workshop Perspectives on Dangerous Climate Change, Tyndall Centre, Norwich, UK, 25(6), doi:10.1111/j.1539-6924.2005.00687.x 1399-1407
     [ Abstract ]

     Defining "dangerous anthropogenic interference" with the climate system in the context of Article 2 of the UN Framework Convention on Climate Change (UNFCCC) presents a complex challenge for those developing long-term climate policy. Natural science has a key role to play in quantifying vulnerabilities of elements of the Earth system and estimating the risks from a changing climate. But attempts to interpret Article 2 will inevitably draw on understanding from social science, psychology, law, and ethics. Here I consider the limits of science in defining climate "danger" by focusing on the potential disintegration of the major ice sheets as an example of an extreme impact. I show that considerations of timescale, uncertainty, and learning preclude a definition of danger drawn purely from natural science. Decision makers will be particularly challenged by one characteristic of global problems: answers to some scientific questions become less accurate over decadal timescales, meandering toward the wrong answer, a feature I call negative learning. I argue for a precautionary approach to Article 2 that would be based initially on current, limited scientific understanding of the future of the ice sheets.

115. Socolow, Robert H., 2005: Can We Bury Global Warming? Scientific American, http://www.princeton.edu/mae/people/faculty/socolow/socdoc/buryglobalwarming.pdf, 293(1), 49-55
     [ Abstract ]

     When William Shakespeare took a breath, 280 molecules out of every million entering his lungs were carbon dioxide. Each time you draw breath today, 380 molecules per million are carbon dioxide. That portion climbs about two molecules every year. No one knows the exact consequences of this upsurge in the atmosphere’s carbon dioxide (CO₂) concentration nor the effects that lie ahead as more and more of the gas enters the air in the coming decades - humankind is running an uncontrolled experiment on the world. Scientists know that carbon dioxide is warming the atmosphere, which in turn is causing sea level to rise, and that the CO₂ absorbed by the oceans is acidifying the water. But they are unsure of exactly how climate could alter across the globe, how fast sea level might rise, what a more acidic ocean could mean, which ecological systems on land and in the sea would be most vulnerable to climate change and how these developments might affect human health and well-being. Our current course is bringing climate change upon ourselves faster than we can learn how severe the changes will be.

116. Thambimuthu, K., M. Soltanieh, J. C. Abanades, R. Allam, O. Bolland, J. Davison, P. Feron, F. Goede, A. Herrera, M. Iijima, D. Jansen, I. Leites, P. Mathieu, E. Rubin, D. Simbeck, K. Warmuzinski, M. Wilkinson, and Robert H. Williams, et al., 2005: Capture of CO₂. Carbon Dioxide Capture and Storage - Chapter 3, a special report of the IPCC, Cambridge University Press, Cambridge, MA, http://www.ipcc.ch/pdf/special-reports/srccs/srccs_chapter3.pdf,
     [ Abstract ]

     The purpose of CO₂ capture is to produce a concentrated stream that can be readily transported to a CO₂ storage site. CO₂ capture and storage is most applicable to large, centralized sources like power plants and large industries. Capture technologies also open the way for large-scale production of low-carbon or carbon-free electricity and fuels for transportation, as well as for small-scale or distributed applications. The energy required to operate CO₂ capture systems reduces the overall efficiency of power generation or other processes, leading to increased fuel requirements, solid wastes and environmental impacts relative to the same type of base plant without capture. However, as more efficient plants with capture become available and replace many of the older less efficient plants now in service, the net impacts will be compatible with clean air emission goals for fossil fuel use. Minimization of energy requirements for capture, together with improvements in the efficiency of energy conversion processes will continue to be high priorities for future technology development in order to minimize overall environmental impacts and cost.
     At present, CO₂ is routinely separated at some large industrial plants such as natural gas processing and ammonia production facilities, although these plants remove CO₂ to meet process demands and not for storage. CO₂ capture also has been applied to several small power plants. However, there have been no applications at large-scale power plants of several hundred megawatts, the major source of current and projected CO₂ emissions. There are three main approaches to CO₂ capture, for industrial and power plant applications. Postcombustion systems separate CO₂ from the flue gases produced by combustion of a primary fuel (coal, natural gas, oil or biomass) in air. Oxy-fuel combustion uses oxygen instead of air for combustion, producing a flue gas that is mainly H₂O and CO₂ and which is readily captured. This is an option still under development. Pre-combustion systems process the primary fuel in a reactor to produce separate streams of CO₂ for storage and H₂ which is used as a fuel. Other industrial processes, including processes for the production of low-carbon or carbon-free fuels, employ one or more of these same basic capture methods. The monitoring, risk and legal aspects associated with CO₂ capture systems appear to present no new challenges, as they are all elements of long-standing health, safety and environmental control practice in industry.
     For all of the aforementioned applications, we reviewed recent studies of the performance and cost of commercial or near-commercial technologies, as well as that of newer CO2 capture concepts that are the subject of intense R&D efforts worldwide. For power plants, current commercial CO₂ capture systems can reduce CO₂ emissions by 80-90% kWh^-1 (85- 95% capture efficiency). Across all plant types the cost of electricity production (COE) increases by 12-36 US$ MWh^-1 (US$ 0.012-0.036 kWh-1) over a similar type of plant without capture, corresponding to a 40-85% increase for a supercritical pulverized coal (PC) plant, 35-70% for a natural gas combined cycle (NGCC) plant and 20-55% for an integrated gasification combined cycle (IGCC) plant using bituminous coal. Overall the COE for fossil fuel plants with capture, ranges from 43-86 US$ MWh^-1, with the cost per tonne of CO₂ ranging from 11- 57 US$/tCO₂ captured or 13-74 US$/tCO₂ avoided (depending on plant type, size, fuel type and a host of other factors). These costs include CO₂ compression but not additional transport and storage costs. NGCC systems typically have a lower COE than new PC and IGCC plants (with or without capture) for gas prices below about 4 US$ GJ^-1. Most studies indicate that IGCC plants are slightly more costly without capture and slightly less costly with capture than similarly sized PC plants, but the differences in cost for plants with CO₂ capture can vary with coal type and other local factors. The lowest CO₂ capture costs (averaging about 12 US$/t CO₂ captured or 15 US$/tCO₂ avoided) were found for industrial processes such as hydrogen production plants that produce concentrated CO₂ streams as part of the current production process; such industrial processes may represent some of the earliest opportunities for CO₂ Capture and Storage (CCS). In all cases, CO₂ capture costs are highly dependent upon technical, economic and financial factors related to the design and operation of the production process or power system of interest, as well as the design and operation of the CO₂ capture technology employed. Thus, comparisons of alternative technologies, or the use of CCS cost estimates, require a specific context to be meaningful.
     New or improved methods of CO₂ capture, combined with advanced power systems and industrial process designs, can significantly reduce CO₂ capture costs and associated energy requirements. While there is considerable uncertainty about the magnitude and timing of future cost reductions, this assessment suggests that improvements to commercial technologies can reduce CO₂ capture costs by at least 20-30% over approximately the next decade, while new technologies under development promise more substantial cost reductions. Realization of future cost reductions, however, will require deployment and adoption of commercial technologies in the marketplace as well as sustained R&D.

117. Wang, X., D. L. Mauzerall, Y. Hu, A. G. Russell, Eric Larson, J.-H. Wood, D. Streets, and A. Guenther, 2005: A High-Resolution Emission Inventory for Eastern China in 2000 and Three Scenarios for 2020. Atmospheric Environment, 39(32), doi:10.1016/j.atmosenv.2005.06.051 5917-5933
     [ Abstract ]

     We develop a source-specific high-resolution emission inventory for the Shandong region of eastern China for 2000 and 2020. Our emission estimates for year 2000 are higher than other studies for most pollutants, due to our inclusion of rural coal consumption, which is significant but often underestimated. Still, our inventory evaluation suggests that we likely underestimate actual emissions. We project that emissions will increase greatly from 2000 to 2020 if no additional emission controls are implemented. As a result, PM2.5 concentrations will increase; however O₃ concentrations will decrease in most areas due to increased NO_X emissions and VOC-limited O₃ chemistry. Taking Zaozhuang Municipality in this region as a case study, we examine possible changes in emissions in 2020 given projected growth in energy consumption with no additional controls utilized (BAU), with adoption of best available end-of-pipe controls (BACT), and with advanced, low-emission coal gasification technologies (ACGT) which are capable of gasifying the high-sulfur coal that is abundant in China. Emissions of NH₃ are projected to be 20% higher, NMVOC50% higher, and all other species 130–250% higher in 2020 BAU than in 2000. Both alternative 2020 emission scenarios would reduce emissions relative to BAU. Adoption of ACGT, which meets only 24% of energy service demand in Zaozhuang in 2020 would reduce emissions more than BACT with 100% penetration. In addition, coal gasification technologies create an opportunity to reduce greenhouse gas emissions by capturing and sequestering CO₂ emissions below ground.

118. Celik, F. E., Eric Larson, and Robert H. Williams, September 2004: Transportation Fuels from Coal with Low CO₂ Emissions. Proceedings of the 7th International Conference on Greenhouse Gas Control Technologies, (GHGT-7), http://www.princeton.edu/~cmi/research/Vancouver04/Celik,Larson,Williams,%20GHGT7,%202004.pdf
     [ Abstract ]

     We present energy and carbon balances and cost estimates based on detailed Aspen Plus process simulations for five plant designs to co-produce dimethyl ether (DME) and electricity from coal. Four of the designs include capture of CO₂ for long-term underground storage. We also illustrate the potential DME offers for reducing emissions by facilitating a shift to more energy-efficient vehicles.

119. Doney, S. C., C. J. Kucharik, and Michael Oppenheimer, 2004: The Influence of Climate on In-stream Removal of Nitrogen. Geophysical Research Letters, 31(L20509), doi:10.1029/2004GL020477
     [ Abstract ]

     Nitrogen (N) removal via benthic denitrification in large river systems can be a significant sink of terrestrial N and a source of nitrous oxide (N₂O) to the atmosphere. Recent studies have demonstrated the fraction of in-stream N removed from a river reach is related to the water residence time. We used the HYDRA aquatic transport model to examine the sensitivity of in-stream N removal and the associated N₂O emissions in the Mississippi River system to the interannual variability in climate. The results suggested an almost two-fold range in the percent of N removed in the Mississippi River system and a three-fold range in the associated N₂O emissions, with the lowest percent removed (10–33%) and the highest N₂O emissions (15.5–26.0 106 kg N) occurring in the wettest years. The results demonstrate the importance of considering climate variability and change in the management of nutrient export by large rivers.

120. Goldenberg, J., T. B. Johansson, A.K.N. Reddy, and Robert H. Williams, 2004: A global clean cooking fuel initiative. Energy for Sustainable Development, VIII(3), doi:10.1016/S0973-0826(08)60462-7 5-12
     [ Abstract ]

     This article calls for engaging the public and private sectors of developing and industrialized countries in a global clean cooking fuel initiative (GCCFI) to bring about a worldwide shift to clean fluid fuels for cooking and heating in 10-15 years’ time -- with an emphasis on providing clean fuel to the poorest households. This initiative is crucial to implementation of the Millennium Development Goals and the Plan of Implementation of the World Summit on Sustainable Development. The article builds on (1) analyses in this special issue of Energy for Sustainable Development of challenges to sustainable development posed by use of solid fuels for cooking and water heating (and for space heating in temperate climates) and opportunities for addressing them by bringing about a shift to clean fluid fuels, and (2) an extensive and compelling literature on the problems posed by this reliance on solid fuels.

121. Gummer MP, The Rt Hon John, C. Butler, E. Claussen, H. Cavalcanti, D. Dillon-Ridgley, D. Gyawali, S. Kato, L. Li, J. Marton-Lefèvre, S. Rayner, T. Smyth, Robert H. Socolow, Sir C. Tickell, and N. Witoszek FitzPatrick, April 2004: Oxford Commission on Sustainable Consumption Report In , Oxford, Mansfield College,
     [ Abstract ]

     The Commission was established in 1999 by the Oxford Centre for the Environment, Ethics and Society (OCEES), then a research institute of Mansfield College in the University of Oxford.
     The report is the product of discussion among members of the Commission in the period 2000-2002, supported by studies by the staff of OCEES, the deliberations of a number of expert workshops and meetings, research projects in Brazil and Nepal, and studies in China, Japan and a number of other countries.
     The subject of sustainable consumption was chosen because, although a question obviously important in itself, it has been given comparatively little attention either by international policymakers or by academics. This is despite the fact that it was considered of real relevance in the conclusions of the Rio Conference of 1992 and highlighted in the work of the Johannesburg Conference ten years later. Although there has been some significant work under the auspices of the United Nations Environment Programme and the Organisation for Economic Co-operation and Development, sustainable consumption needs a good deal of further work if satisfactory policies are to be developed.

122. Keller, Klaus, B. M. Bolker, and David F. Bradford, 2004: Uncertain climate thresholds and optimal economic growth. Journal of Environmental Economics and Management, 48(1), doi:10.1016/j.jeem.2003.10.003 723-741
     [ Abstract ]

     We explore the combined effects of a climate threshold (a potential ocean thermohaline circulation collapse), parameter uncertainty, and learning in an optimal economic growth model. Our analysis shows that significantly reducing carbon dioxide (CO₂) emissions may be justified to avoid or delay even small (and arguably realistic) damages from an uncertain and irreversible climate change—even when future learning about the system is considered. Parameter uncertainty about the threshold specific damages and the CO₂ level triggering a threshold can act to decrease near-term CO₂ abatements that maximize expected utility.

123. Kim, S.-R., Klaus Keller, and David F. Bradford, July 2004: Optimal Technological Portfolios for Climate-Change Policy under Uncertainty: A Computable General Equilibrium Approach. Computing in Economics and Finance 2004, Society for Computational Economics, http://ideas.repec.org/p/sce/scecf4/140.html,
     [ Abstract ]

     When exploring solutions to long-term environmental problems such as climate change, it is crucial to understand how the rates and directions of technological change may interact with environmental policies in the presence of uncertainty. This paper analyzes optimal technological portfolios for global carbon emissions reductions in an integrated assessment model of the coupled social-natural system. The model used here is a probabilistic, two-technology extension of Nordhaus’ earlier model (Nordhaus and Boyer, 2000) by incorporating endogenous technological choice between conventional and carbon-free technologies. Taking into account the possible competitions among the technological options, we address the issues of optimal timing, costs and burden-sharing of optimal carbon mitigation strategies in the inherently uncertain world. We perform various analyses related to the major uncertainties about natural, socioeconomic and technological parameters, and investigate the effects of uncertainties resolution, risks and alternative political preferences. The results show that analyses ignoring uncertainty could lead to inefficient and biased technology-policy recommendations for the future.

124. Kim, S.-R., 2004: Uncertainty, Political Preferences, and Stabilization: Stochastic Control Using Dynamic CGE Models. Computational Economics,
     [ Abstract ]

     This paper is a step toward the merger of optimal control models with dynamic computable general equilibrium (CGE) models. It demonstrates the usefulness of CGE techniques in control theory application and provides a practical guideline to policymakers in this relatively new field. Uncertainty, short-term quantity adjustment processes, and sector-specific political preferences are taken into account in exploring what time paths of adjustments of the economy would be optimal for a government with explicit policy goals. The experimental results highlight the importance of the structures of political preferences and uncertainty when performing optimal stabilization policy exercises.

125. Kim, S.-R., 2004: Environmental Taxes and Economic Welfare: The Welfare Cost of Gasoline Taxation in the U.S. 1959-1999. ICFAI Journal of Environmental Economics, II(1),
     [ Abstract ]

     The purpose of this paper is to provide reasonable estimates for the welfare cost of environmental tax reform in the US economy. Unlike most previous studies that empirically evaluate the deadweight cost of taxation, the model employed here considers explicitly the joint allocation of leisure and commodity demands where the wage rate plays a role both as a form of income and as the price of leisure time. The estimated results of the consumer behavior model indicate that the existing US gasoline tax regime has induced a decrease of gasoline consumption by approximately 4% over the period from 1959 to 1999, while the deadweight cost caused by the tax accounts just for about 0.08% of the consumer full income over the sample period 1959-1999. Moreover, in most years of the sample period, the measures of marginal deadweight cost of gasoline taxation (sample average 0.1882) are relatively small compared to those of labor taxation (sample average 0.2175). This implies a larger efficiency gain in the case of labor taxation in shifting from the existing distortionary taxation to lump sum taxation. These empirical results might suggest the modest possibility of social welfare gains from tax reforms that would shift some of the burden of taxation from labor to energy (e.g., gasoline).

126. Kreutz, Thomas, and Robert H. Williams, September 2004: Competition Between Coal and Natural Gas in Producing H₂ and Electricity under CO₂ Emission Constraints. Proceedings of the 7th International Conference on Greenhouse Gas Control Technologies, (GHGT-7), http://www.princeton.edu/~cmi/research/Vancouver04/Kreutz%20-%20Williams%20,
     [ Abstract ]

     This study explores the competition between coal and natural gas in the large scale production of electricity and H₂ in a world with severe constraints on greenhouse gas emissions. We examine the economic conditions that fa-vor: 1) CO₂ capture vs. CO₂ venting, and 2) coal versus natural gas as the primary energy source, by varying the magnitude of an assumed carbon tax, the price of natural gas, and capacity factor of natural gas combined cycle (NGCC) plants. Coal-based conversion focuses on gasification: electricity from integrated gasifier combined cycle (IGCC) plants, and H₂ + electricity from gasification-based plants; both pure CO₂ capture and storage (CCS) and (the potentially less costly) co-capture and co-storage of H₂S+CO₂ are considered. We also examine the effect of 3 Party Covenant financing, a public subsidy for encouraging the commercial adoption of IGCC. The natural gas (NG) systems considered are NGCC for electricity and steam methane reforming for H₂ production.

127. Min, D.-H., and Klaus Keller, 2004: How robust are estimated decadal-scale trends in dissolved oxygen concentrations in the Southern Ocean with respect to methodological assumptions? EOS Trans. AGU, 84(52),
     [ Abstract ]

     The Southern Ocean (SO) plays a central role in deep water formation as well as oceanic heat and carbon dioxide uptake. Several modeling studies suggest considerable circulation changes in the SO over the past few decades in response to anthropogenic carbon dioxide emissions. These circulation changes are accompanied - in the models - by a substantial decrease of dissolved oxygen concentrations. Detailed analysis of temporal and spatial changes of dissolved oxygen in the SO may hence be a promising method to detect the ocean's response to climate change. The few observational studies estimating decadal scale oxygen trends in the SO come, however, to different conclusions. Here, we analyze different statistical methods to estimate decadal scale [O₂] trends in the SO. In a companion study (Keller et al., 2004), we use the most robust method to estimate SO oxygen trends.

128. Moles, C. G., J. R. Banga, and Klaus Keller, 2004: Solving nonconvex climate control problems: Pitfalls and algorithm performances. Applied Soft Computing, 5(1), doi:10.1016/j.asoc.2004.03.011 35-44
     [ Abstract ]

     Global optimization can be used as the main component for reliable decision support systems. In this contribution, we explore numerical solution techniques for nonconvex and nondifferentiable economic optimal growth models. As an illustrative example, we consider the optimal control problem of choosing the optimal greenhouse gas emissions abatement to avoid or delay abrupt and irreversible climate damages. We analyze a number of selected global optimization methods, including adaptive stochastic methods, evolutionary computation methods and deterministic/hybrid techniques. Differential evolution (DE) and one type of evolution strategy (SRES) arrived to the best results in terms of objective function, with SRES showing the best convergence speed. Other simple adaptive stochastic techniques were faster than those methods in obtaining a local optimum close to the global solution, but mis-converged ultimately.

129. O'Neill, B., and Michael Oppenheimer, 2004: Climate Change Impacts Sensitive to Path to Stabilization. Proceedings of the National Academy of Sciences of the United States of America, 101, doi:10.1073/pnas.0405522101 16411-16416
     [ Abstract ]

     Analysis of policies to achieve the long-term objective of the United Nations Framework Convention on Climate Change, stabilizing concentrations of greenhouse gases at levels that avoid ‘‘dangerous’’ climate changes, must discriminate among the infinite number of emission and concentration trajectories that yield the same final concentration. Considerable attention has been devoted to path-dependent mitigation costs, generally for CO₂ alone, but not to the differential climate change impacts implied by alternative trajectories. Here, we derive pathways leading to stabilization of equivalent CO₂ concentration (including radiative forcing effects of all significant trace gases and aerosols) with a range of transient behavior before stabilization, including temporary overshoot of the final value. We compare resulting climate changes to the sensitivity of representative geophysical and ecological systems. Based on the limited available information, some physical and ecological systems appear to be quite sensitive to the details of the approach to stabilization. The likelihood of occurrence of impacts that might be considered dangerous increases under trajectories that delay emissions reduction or overshoot the final concentration.

130. Ogden, J. M., Robert H. Williams, and Eric Larson, 2004: Societal Lifecycle Costs of Cars with Alternative Fuels/Engines. Energy Policy, 32(1), doi:10.1016/S0301-4215(02)00246-X 7-27
     [ Abstract ]

     Effectively addressing concerns about air pollution (especially health impacts of small-particle air pollution), climate change, and oil supply insecurity will probably require radical changes in automotive engine/fuel technologies in directions that offer both the potential for achieving near-zero emissions of air pollutants and greenhouse gases and a diversification of the transport fuel system away from its present exclusive dependence on petroleum. The basis for comparing alternative automotive engine/fuel options in evolving toward these goals in the present analysis is the ‘‘societal lifecycle cost’’ of transportation, including the vehicle first cost (assuming large-scale mass production), fuel costs (assuming a fully developed fuel infrastructure), externality costs for oil supply security, and damage costs for emissions of air pollutants and greenhouse gases calculated over the full fuel cycle. Several engine/fuel options are considered—including current gasoline internal combustion engines and a variety of advanced lightweight vehicles: internal combustion engine vehicles fueled with gasoline or hydrogen; internal combustion engine/hybrid electric vehicles fueled with gasoline, compressed natural gas, Diesel, Fischer–Tropsch liquids or hydrogen; and fuel cell vehicles fueled with gasoline, methanol or hydrogen (from natural gas, coal or wind power). To account for large uncertainties inherent in the analysis (for example in environmental damage costs, in oil supply security costs and in projected mass-produced costs of future vehicles), lifecycle costs are estimated for a range of possible future conditions. Under base-case conditions, several advanced options have roughly comparable lifecycle costs that are lower than for today’s conventional gasoline internal combustion engine cars, when environmental and oil supply insecurity externalities are counted - including advanced gasoline internal combustion engine cars, internal combustion engine/hybrid electric cars fueled with gasoline, Diesel, Fischer– Tropsch liquids or compressed natural gas, and hydrogen fuel cell cars. The hydrogen fuel cell car stands out as having the lowest externality costs of any option and, when mass produced and with high valuations of externalities, the least projected lifecycle cost. Particular attention is given to strategies that would enhance the prospects that the hydrogen fuel cell car would eventually become the Car of the Future, while pursuing innovations relating to options based on internal combustion engines that would both assist a transition to hydrogen fuel cell cars and provide significant reductions of externality costs in the near term.

131. Oppenheimer, Michael, and R. B. Alley, 2004: The West Antarctic Ice Sheet and Long Term Climate Policy. Climatic Change, 64(1-2), doi:10.1023/B:CLIM.0000024792.06802.31 1-10
     [ Abstract ]

     Disintegration of the West Antarctic ice sheet (WAIS) has long served as a benchmark of dangerous climate change (Mercer, 1968, 1978; Revelle, 1983; Smith et al., 2001). Recent findings with implications for the future of the West Antarctic ice sheet in a warming world (Rott et al., 2002; De Angelis and Skvarca, 2003) may be of importance to policy makers and others (Berk et al., 2002) grappling with the meaning of Article 2 of the U.N. Framework Convention on Climate Change and its injunction to avoid ‘dangerous anthropogenic interference with the climate system.’ These observations show acceleration of glaciers coupled to abrupt ice-shelf disintegration along the Antarctic Peninsula (Doake et al., 1998). The key issue is whether the main body of the ice sheet would behave similarly if its ice shelves were thinned or removed by a warming climate. The accompanying editorial essay by Dessai et al. (2004) argues ‘internal definitions of dangerous climate change –“danger as experienced” – warrants at least as much attention as external definitions – “danger as defined” ’. We agree that the interpretation of Article 2 ought to expand beyond traditional approaches grounded in climatology, biology, economics and engineering. The editorial further states ‘it is not possible to make progress on defining dangerous climate change, or in developing sustainable responses to this global problem, without recognising the central role played by social or individual perceptions of danger.’ There is a substantial risk in adopting the latter view. Addressing the psychological and much of the social dimension of dangerous climate change is in its infancy in comparison to the decades-old process of physical assessment. An equally prolonged discussion of the social and psychological dimension is in the offing. The continuing increase in greenhouse gas concentrations could make certain dangers unavoidable unless a preliminary interpretation of Article 2, based largely on the ‘external’ framework, is implemented (O’Neill and Oppenheimer, 2002). In practice, such an approach already may be feasible for a handful of climate changes, such as the ‘large-scale discontinuities’ (e.g. disintegration of WAIS, shutdown of the thermohaline circulation) noted in the Third Assessment Report of the Intergovernmental Panel on Climate Change (Smith et al., 2001). The recent glaciological findings provide an opportunity to consider how a long-term objective consistent with Article 2 might be selected, because they shed new light on the range of climate change that may trigger disintegration of WAIS. Here we explore the key scientific issues and consider a long-term approach to limiting greenhouse gas concentrations based upon these observations, tied to the viability of the major West Antarctic ice shelves.We believe the consequences of a WAIS collapse would be so large that despite uncertainties, external considerations supplemented by a precautionary interpretation of the recent observations may be sufficient to define dangerous levels of climate change, and the corresponding greenhouse gas (ghg) concentrations.

132. Oppenheimer, Michael, 2004: Book Review: The Discovery of Global Warming. Journal of Environmental History, 9, 327-328
     [ Abstract ]

     As a scientific problem, global warming has a history dating back at least to Fourier in 1827. Its origins as a political issue are much more recent, with serious discussions of limiting greenhouse gas emissions beginning among scientists and economists only in the middle of the 1970s when the prospect of warming vied on an equal footing with the possibility of future cooling of the planet. Policy makers came to the table a decade later. The evolution of the climate question from science to politics and back and forth has been the subject of surprisingly few in-depth treatments. This void leads to a damaging lack of perspective in the public debate. Without the context of history, assertions like "not long ago, the same scientists who now warn us of warming were alarmists over global cooling" or "global warming is a left wing plot hatched by anti-capitalist environmentalists" too often go unchallenged. Spencer Weart's The Discovery of Global Warming goes a long way toward rectifying this situation. Weart, director of the Center for the History of Physics at the American Institute of Physics, is most effective at laying out the early scientific developments, and discussing how scientists moved the issue onto governmental research agendas. He is somewhat less effective in describing political developments once the issue veered squarely into the policy arena. Weart highlights the importance of the actions of networks of scientists in constructing a bridge from science to policy on an arcane issue of no apparent urgency to the general public. He correctly points to the key leadership role of Swedish climatologist Bert Bolin in shepherding his colleagues toward consensus, beginning in the late 1960s. Weart's exploration of the science-policy interaction in the 1970s, which focused largely on increasing support for research, is thorough. His discussion of scientists' activity after the mid-1980s, which helped build the road to the U.N. Framework Convention on Climate Change and the Kyoto Protocol, is more superficial. One of the most useful features of this book is the timeline of events following the last chapter. Oddly, it ends at 1988 because "the period since 1988 is too recent to identify historical milestones." Perhaps this is a valid assertion from a historian's professional viewpoint. But the importance of some events, like the signing of the Framework Convention in 1992, is likely to endure. In contrast, the author is quite willing to highlight scientific questions, like the potential importance of warming-induced shifts in the major ocean circulation, whose significance also may not become clear for decades. But never mind these shortcomings. The clear value of this book to scholars, reporters, and the interested public will hopefully spawn additional efforts that will fill these gaps, and lead to a greater understanding of scientists as political actors. The Discovery of Global Warming has done us all a great favor by pointing the way.

133. Oppenheimer, Michael, September 2004: Reinvigorating the Kyoto System and Beyond: Maintaining the Fundamental Architecture, Meeting Long-Term Goals. Leaders’ Summit on Post-Kyoto Architecture: Toward an L20, http://www.princeton.edu/step/people/faculty/michael-oppenheimer/recent-publications/,
     [ Abstract ]

     While it is increasingly clear that anthropogenic emissions of greenhouse gases (GHGs) are causing potentially irreversible shifts in Earth's climate, efforts to craft a durable and effective architecture for addressing the problem remain stymied by deep divisions between north and south, between major emitting nations and those that will be most affected by global warming, between some nations that are heavily export-dependent on fossil fuels and the rest of the world. Even within governments, disagreements among different ministries with different mandates have stalled action. This delay is not without cost: every year that nations postpone action to reverse GHG emissions growth and bring forward a robust response, the time window for averting dangerous levels of climate change narrows. The L20 provides a potentially important forum that could offer much needed global leadership on innovative approaches for overcoming international divisions on this crucial challenge. In particular, L20 leaders' experience in strengthening the world's international financial architecture provides an important lens through which to view new approaches for the international market-based architecture to reduce GHG emissions. The following paper proposes, for L20 consideration, three approaches to rejuvenating the United Nations Framework Convention on Climate Change (UNFCCC) and its Kyoto process. We ground our argument in these integrated assumptions: The incentive-based architecture that was incorporated, if imperfectly, in the Kyoto Protocol provides an optimal basis to broaden participation and develop a viable long term approach to address climate change. Further, we assert that the Kyoto formulation of successive near-term (decade-scale) targets for limiting total emissions of greenhouse gases (GHGs) provides a necessary element for achieving the long-term goal of the UNFCCC (stated in its Article 2). Our analysis is motivated by three main objectives: 1) US participation, 2) developing country/non-Annex I participation,1 and 3) coupling near-term obligations of the Parties to an effective long-term strategy for limiting climate change.

134. Pacala, Stephen W., and Robert H. Socolow, 2004: Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies. Science, 305, doi:10.1126/science.1100103 968-972
     [ Abstract ]

     Humanity already possesses the fundamental scientific, technical, and industrial know-how to solve the carbon and climate problem for the next half-century. A portfolio of technologies now exists to meet the world’s energy needs over the next 50years and limit atmospheric CO₂ to a trajectory that avoids a doubling of the preindustrial concentration. Every element in this portfolio has passed beyond the laboratory bench and demonstration project; many are already implemented somewhere at full industrial scale. Although no element is a credible candidate for doing the entire job (or even half the job) by itself, the portfolio as a whole is large enough that not every element has to be used. The debate in the current literature about stabilizing atmospheric CO₂ at less than a doubling of the preindustrial concentration has led to needless confusion about current options for mitigation. On one side, the Intergovernmental Panel on Climate Change (IPCC) has claimed that “technologies that exist in operation or pilot stage today” are sufficient to follow a less-thandoubling trajectory “over the next hundred years or more” [(1), p. 8]. On the other side, a recent review in Science asserts that the IPCC claim demonstrates “misperceptions of technological readiness” and calls for “revolutionary changes” in mitigation technology, such as fusion, space-based solar electricity, and artificial photosynthesis (2). We agree that fundamental research is vital to develop the revolutionary mitigation strategies needed in the second half of this century and beyond. But it is important not to become beguiled by the possibility of revolutionary technology. Humanity can solve the carbon and climate problem in the first half of this century simply by scaling up what we already know how to do. 13

135. Socolow, Robert H., R. Hotinski, J. B. Greenblatt, and Stephen W. Pacala, December 2004: Solving the Climate Problem: Technologies Available to Curb CO₂ Emissions. Environment, http://www.princeton.edu/~cmi/resources/CMI_Resources_new_files/Environ_08-21a.pdf, 46(10), 8-19
     [ Abstract ]

     The atmosphere’s concentration of carbon dioxide (CO₂) has increased by more than 30 percent over the last 250 years, largely due to human activity. Two-thirds of that rise has occurred in the past 50 years.1 Unless there is a change, the world will see much higher CO₂ levels in the future—levels that are predicted to lead to damaging climate change. Fortunately, many carbon mitigation strategies are available to set the world on a new path, one that leads to a lower rate of CO₂ emissions than is currently expected. The environmental community is currently playing a prominent role in the development of the CO₂ policies that will elicit these strategies. Until a few years ago, the environmental community was almost exclusively interested in policies that promote renewable energy, conservation, and natural sinks. More recently, it has begun to explore alliances with traditional energy supply industries on the grounds that to establish the pace required to achieve environmental goals, parallel action on many fronts is required.

136. Socolow, Robert H., 2004: co-author, The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs. Board of Energy and Environmental Systems, Washington, DC, National Academy Press, (ISBN - 10:0-309-0916),
     [ Abstract ]

     The announcement of a hydrogen fuel initiative in the President’s 2003 State of the Union speech substantially increased interest in the potential for hydrogen to play a major role in the nation’s long-term energy future. Prior to that event, DOE asked the National Research Council to examine key technical issues about the hydrogen economy to assist in the development of its hydrogen R&D program. Included in the assessment were the current state of technology; future cost estimates; CO₂ emissions; distribution, storage, and end use considerations; and the DOE RD&D program. The report provides an assessment of hydrogen as a fuel in the nation’s future energy economy and describes a number of important challenges that must be overcome if it is to make a major energy contribution. Topics covered include the hydrogen end-use technologies, transportation, hydrogen production technologies, and transition issues for hydrogen in vehicles.

137. Socolow, Robert H., Stephen W. Pacala, and J. B. Greenblatt, September 2004: Wedges: Early Mitigation with Familiar Technology. Proceedings of the 7th International Conference on Greenhouse Gas Control Technologies, (GHGT-7), http://www.princeton.edu/~cmi/research/Vancouver04/socolow%20poster.pdf,
     [ Abstract ]

     If the world is willing to accept a tripling of the pre-industrial atmospheric CO₂ concentration, significant carbon mitigation can be delayed for most of the next half century. If the world is to be put on a path to avoid a doubling, however, a monumental mitigation effort needs to start now. To convey the magnitude of the effort, we introduce the “wedge” as the unit of mitigation: a wedge is an activity that creates 1 GtC/y of carbon emission reductions in 2054, relative to a world unconcerned about global carbon emissions. To pursue 500 ppm stabilization, the task for the next 50 years is to achieve about seven wedges by avoiding about 175 billion tons of carbon emissions.

138. Williams, Robert H., December 2004: IGCC: Next Steps on the Path to Gasification-Based Energy from Coal. Expanding Energy Supply, in The National Commission on Energy Policy, http://www.bipartisanpolicy.org/sites/default/files/TA_C4.pdf, (Chapter 2), 351-381
     [ Abstract ]

     The integrated gasifier combined cycle (IGCC) makes it feasible to provide coal electricity as cleanly as natural gas combined cycle (NGCC) plants and to deal with the climate challenge via CO₂ capture and storage (CCS) with much lower energy and cost penalties than with coal steam-electric technologies. Moreover, IGCC is a stepping stone to provision of clean, secure, and climate-friendly supplies of synthetic fuels manufactured via gasification of coal and biomass with capture and storage underground of CO₂—synthetic fuels that will often be provided in polygeneration plants that also make electricity, as well as chemicals and process steam. Although IGCC technology has evolved to the point where electricity generation costs based on use of bituminous coals are about the same as for steam-electric plants, there are three major institutional challenges that must be overcome. The first is that coal IGCC technology is not likely to be launched in the market without appropriate promotion by the public sector, because much of what the technology offers are public (rather than private) benefits not yet reflected in energy market prices. The second is that, although all components of current IGCC CO₂ capture (CC) systems are fully proven and commercially available, no IGCC systems with CC have been built. Early field experience with CC technologies is needed even before a climate mitigation policy is put into place. The third is that the concept of a major future for coal in a climate-constrained world hinges on the viability of CO₂ storage at “gigascale”—the determination of which requires, along with more R&D on CO₂ storage, the conduct of many “megacale” CO₂ storage demonstration projects during the next 10-15 years.

139. Williams, Robert H., December 2004: Toward Polygeneration of Fluid Fuels and Electricity via Gasification of Coal and Biomass. Expanding Energy Supply, in The National Commission on Energy Policy, http://www.bipartisanpolicy.org/sites/default/files/TA_C4.pdf, (Chapter 4), 497-520
     [ Abstract ]

     The major challenges posed by transportation fuels are oil supply insecurity, the prospect of sustained high oil prices, health effects of air pollution, and the climate change risks posed by the buildup in the atmosphere of CO₂ from fossil fuel burning. The oil issues are the most pressing, and the climate challenge is the most daunting. The problems cannot be solved without radical changes in our transportation energy system—and getting started as soon as possible. A strategy for dealing effectively with these challenges in this quarter century is described. The elements of the strategy are: (i) bringing about a shift to energy-efficient hybrid-electric vehicles, (ii) the production of ultra-clean “designer” synthetic fuel from coal and biomass via gasification, and (iii) capture and underground storage of the CO₂ byproduct of synthetic fuel manufacture. This strategy makes it feasible to provide substantial quantities of clean liquid fuels for transportation without using oil, with ultra-low greenhouse gas emissions, without having to shift to a hydrogen economy, and with far less land than is required with fluid fuels produced from biomass only.

140. Williams, Robert H., 2004: $1 a Gallon Synthetic Liquid Fuel with the GHG Emission Rate of Hydrogen. , Unpublished
141. Keller, Klaus, D.-H. Min, and R. M. Key, 2003: Detecting decadal-scale oxygen trends in the Southern Ocean. EOS Trans. AGU, 84(52),
     [ Abstract ]

     Several modeling studies suggest a significant oxygen loss of the Southern Ocean over the last few decades. The main cause is a decrease in Southern Ocean ventilation due to climate change. The model predictions of generally decreasing Southern Ocean oxygen concentrations are consistent with the few available observational studies in a small fraction of the Southern Ocean. The observational studies suggest, however, different mechanisms to explain the decreased oxygen concentrations (e.g. changes in water mass fractions or changes in the water density structure). A mechanistic understanding of the Southern Ocean oxygen inventory is critical to predictions of the oceanic response to global climate change. For example, a decreased Southern Ocean ventilation in response to anthropogenic carbon dioxide emissions would cause a decreased oceanic heat and carbon dioxide uptake - a positive climate feedback. Further, an oceanic oxygen loss would bias estimates of the oceanic carbon dioxide sink derived from atmospheric oxygen observations. Here, we estimate decadal-scale dissolved oxygen trends in the Southern Ocean and their statistical relevance using the WOD 2001 hydrographic database. We explore several hypotheses regarding the driving mechanisms for the observed concentration trends and estimate the changes in the total oxygen inventory of the Southern Ocean.

142. Kraepiel, A. M., Klaus Keller, H. B. Chin, E. G. Malcolm, and Francois Morel, 2003: Sources and Variations of Mercury in Tuna. Environmental Science and Technology, 37, doi:10.1021/es0340679 5551-5558
     [ Abstract ]

     While the bulk of human exposure to mercury is through the consumption of marine fish, most of what we know about mercury methylation and bioaccumulation is from studies of freshwaters. We know little of where and how mercury is methylated in the open oceans, and there is currently a debate whether methylmercury concentrations in marine fish have increased along with global anthropogenic mercury emissions. Measurements of mercury concentrations in Yellowfin tuna caught off Hawaii in 1998 show no increase compared to measurements of the same species caught in the same area in 1971. On the basis of the known increase in the global emissions of mercury over the past century and of a simple model of mercury biogeochemistry in the Equatorial and Subtropical Pacific ocean, we calculate that the methylmercury concentration in these surface waters should have increased between 9 and 26% over this 27 years span if methylation occurred in the mixed layer or in the thermocline. Such an increase is statistically inconsistent with the constant mercury concentrations measured in tuna. We conclude tentatively that mercury methylation in the oceans occurs in deep waters or in sediments.

143. Mann, M. E., C. M. Ammann, R. S. Bradley, K. R. Briffa, T. J. Crowley, M. K. Hughes, P. D. Jones, Michael Oppenheimer, T. J. Osborn, J. T. Overpeck, S. Rutherford, K. E. Trenberth, and T.M.L. Wigley, 2003: On past temperatures and anomalous late-20th century warmth. EOS Trans. AGU, 84, doi:10.1029/2003EO270003 256
     [ Abstract ]

     Evidence from paleoclimatic sources and modeling studies support AGU's official position statement on "Climate Change and Greenhouse Gases," that there is a compelling basis for concern over future climate changes, including increases in global-mean surface temperatures, due to increased concentrations of greenhouse gases, primarily from fossil-fuel burning. More specifically, a number of reconstructions of large-scale temperature changes over the past millennium support the conclusion that late-20th century warmth was unprecedented over at least the past millennium. Modeling and statistical studies indicate that such anomalous warmth cannot be fully explained by natural factors but, instead, require a significant anthropogenic forcing of climate that emerged during the 19th and 20th centuries.
     Two (nearly identical) recent papers [Soon and Baliunas, 2003 and Soon et al., 2003--henceforth both referred to as 'SB03'] challenge this view, and have been used to support the claim that recent hemispheric-scale warmth is not unprecedented in the context of the past millennium (see e.g. "20th Century Climate Not So Hot", press-release, Harvard-Smithsonian Center for Astrophysics, March 31, 2003: http://cfa-www.harvard.edu/press/pr0310.html). Such claims are inconsistent with the preponderance of scientific evidence. We therefore review these claims in the light of the fact that they have found their way into the media and have been read into the U.S. Senate record.

144. Moles, C. G., A. S. Lieber, J. R. Banga, and Klaus Keller, 2003: Global optimization of climate control problems using evolutionary and stochastic algorithms. Advances in Soft Computing: Engineering Design and Manufacturing, Springer-Verlag, Heidelberg, http://www.geosc.psu.edu/~kkeller/Moles_asc_02.pdf, 331-342
     [ Abstract ]

     Global optimization can be used as the main component for reliable decision support systems. In this contribution, we explore numerical solution techniques for nonconvex and nondifferentiable economic optimal growth models. As an illustrative example, we consider the optimal control problem of choosing the optimal greenhouse gas emissions abatement to avoid or delay abrupt and irreversible climate damages. We analyze a number of selected global optimization methods, including adaptive stochastic methods, evolutionary computation methods and deterministic/ hybrid techniques. Differential evolution (DE) and one type of evolution strategy (SRES) arrived to the best results in terms of objective function, with SRES showing the best convergence speed. Other simple adaptive stochastic techniques were faster than those methods in obtaining a local optimum close to the global solution, but misconverged ultimately.

145. Nævdal, E., 2003: Optimal Regulation Of Natural Resources In The Presence Of Irreversible Threshold Effects. Natural Resource Modeling, http://www3.interscience.wiley.com/journal/119823168/abstract, 16(3), 305-333
     [ Abstract ]

     Thresholds are an important physical consideration in the regulation of natural resources. This paper is the first to present a complete analytical framework in which to evaluate optimal regulation of a natural resource in the presence of irreversible threshold effects. Necessary conditions are presented for optimal regulation of these problems both for when the threshold has a known location in state-space and for when the location of the threshold is unknown. In the case where the location is known, the literature is corrected on a seemingly minor technical point regarding the behavior of the co-state variables that turns out to be of considerable importance. For the case when the location of the threshold is not known, it is shown that thresholds in state-space implies a nonstandard risk structure.

146. Oppenheimer, Michael, 2003: Atmospheric Pollution: History, Science, and Regulation. Physics Today, http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=p, 56, 65-66
     [ Abstract ]

     Scientific and political interest in atmospheric pollution, as well as attempts to regulate it, have expanded from local to regional to global scales over the three decades since the passage of the US Clean Air Act of 1970. Acid deposition, ozone depletion, regional-scale smog, and global warming – unknown or little understood before 1970 – are at the center of atmospheric research, domestic regulation, and international affairs. With regard to international affairs, witness the broad effect on US-European relations of the Bush administration’s rejection of the Kyoto Protocol on climate change.

147. Oppenheimer, Michael, and A. Petsonk, 2003: Global Warming: Formulating Long Term Goals. Climate Policy Beyond Kyoto: Meeting the Long Term Challenge of Global Warming, http://www.princeton.edu/~cmi/research/Policy/Papers/oppenheimer.pdf,
     [ Abstract ]

     In this paper we explore the origins and potential implementation of long term climate objectives and the particular concept of “dangerous anthropogenic interference with the climate system,” outlined in Article 2 of the Framework Convention. We show that the need for a long term perspective and also its specific framing in the form of Article 2 reflects views held on both sides of the Atlantic from the earliest days of the climate issue. We review the evolution of the concept of “dangerous” and the various proposals for implementing Article 2 as a regulatory regime. It is here that we find the greatest potential for transatlantic differences, arising from differing governmental views on risk and uncertainty. We argue that these potential differences need to be addressed quickly so that current conceptions of what constitutes “dangerous” can play a significant role in determining near term, as well as long-term, climate policy. That is, policy approaches that address “stabilization of concentrations” and those that address near term emissions limitations should be considered together.

148. Socolow, Robert H., 2003: Review of DOE’s Vision 21 Research and Development Program, Phase I (contributor) In , Washington, DC, National Academy Press, (ISBN-10: 0-309-08717),
     [ Abstract ]

     The Vision 21 Program is a relatively new research and development (R&D) program. It is funded through the U.S. Department of Energy’s (DOE’s) Office of Fossil Energy and its National Energy Technology Laboratory (NETL). The Vision 21 Program Plan anticipates that Vision 21 facilities will be able to convert fossil fuels (e.g., coal, natural gas, and petroleum coke) into electricity, process heat, fuels, and/or chemicals cost effectively, with very high efficiency and very low emissions, including of the greenhouse gas carbon dioxide (CO2) (DOE, 1999a). Planning for the program began to take shape in 1998 and 1999. Since then, workshops have been held, proposals for projects have been funded, and roadmaps have been developed for each of the key technologies considered to be part of the Vision 21 effort. Vision 21 is focused on the development of advanced technologies that would be ready for deployment in 2015.
     Vision 21 as it currently stands is not per se a line item in the Office of Fossil Energy budget but, rather, a collection of projects that contribute to the technologies required for Vision 21 energy plants. Vision 21 management estimates that about $50 million was expended in fiscal year (FY) 2002 on Vision 21 projects and activities. These projects have come about not only as a result of a Vision 21 solicitation by DOE/NETL but also as an outgrowth of ongoing R&D activities in the traditional Office of Fossil Energy coal and power systems program. Ongoing activities that are oriented to achieving revolutionary rather than evolutionary improvements in performance and cost and that share common objectives with Vision 21 are considered to be part of the Vision 21 Program and activities. Thus, Vision 21 activities must be coordinated across a suite of activities in DOE and NETL programs contained in the Office of Fossil Energy’s R&D programs on coal and power systems. This coordination is partially achieved through a matrix management structure at NETL, and the responsibility for managing Vision 21 is vested in a small steering committee.
     The goals of Vision 21 are extremely challenging and ambitious. As noted in the Vision 21 Technology Roadmap, if the program meets its goals, Vision 21 plants would essentially eliminate many of the environmental concerns traditionally associated with the conversion of fossil fuels into electricity and transportation fuels or chemicals (NETL, 2001). Given the importance of fossil fuels, and especially coal, to the economies of the United States and other countries and the need to utilize fossil fuels in an efficient and environmentally acceptable manner, the development of the technologies in the Vision 21 Program is a high priority.
     This report contains the results of the second National Research Council (NRC) review of the Vision 21 R&D Program. The first review of the program was conducted by the NRC Committee on R&D Opportunities for Advanced Fossil-fueled Energy Complexes. It resulted in the report Vision 21, Fossil Fuel Options for the Future, which was published in the spring of 2000 (NRC, 2000). At that time, the Vision 21 Program was in an embryonic stage, having been initiated by DOE in 1998-1999. The NRC report contained a number of recommendations for DOE to consider as it moved forward with its program; DOE’s responses to many of these recommendations are considered in Chapter 3. Now, 2 years after the first review, DOE’s Deputy Assistant Secretary for Coal and Power Systems requested that the NRC again review progress and activities in the Vision 21 Program. In response, the NRC formed the Committee to Review DOE’s Vision 21 R&D Program—Phase I. Most of the members of this committee also served on the committee that wrote the earlier report (see Appendix A for committee biographical information).
     The present report is organized into three chapters. Chapter 1 introduces the Vision 21 Program and presents background information. Chapter 2 presents strategic recommendations for the program as a whole. Chapter 3 focuses on the individual technologies. This Executive Summary brings forward from Chapter 2 three major issues that the committee believes are of the highest priority from a programwide strategic standpoint—namely, what the focus of the program should be, how it should be empowered to accomplish its goals, and what analytic capabilities it should have to evaluate technological approaches for reaching its goals. At the same time, it reiterates the five most important of the nine recommendations in that chapter. Also, based on the premise that some of the technologies in Chapter 3 are more essential than others to realizing Vision 21 goals, the committee selected five high-priority recommendations from that chapter and reiterates them here in the Executive Summary.

149. Socolow, Robert H., 2003: The Century-Scale Problem of Carbon Management. The Carbon Dioxide Dilemma: Promising Technologies and Policies. Proceedings of a Symposium, Washington, DC, The National Academies Press, (ISBN-10: 0-309-08921), 11-14
     [ Abstract ]

     There are six important things to remember about the greenhouse problem and carbon management. 1. The greenhouse problem is a century-scale problem. 2. From a one-century perspective, the characteristics of fossil fuel production look complex and unfamiliar. 3. Hydrogen is intimately connected with carbon management. 4. Early action on the permitting of CO₂ storage sites will reveal many difficult, largely unresolved issues. 5. Carbon management is not a winner-take-all strategy. 6. Carbon management confronts us with ethical issues.

150. Socolow, Robert H., et al., June 2003: Responses to the invitation to a discussion on the Sao Paulo Declaration. Energy for Sustainable Development, 7(2), doi:10.1016/S0973-0826(08)60351-8 23-24
     [ Abstract ]

     The invitation in Volume VI No. 2 (June 2002) of Energy for Sustainable Development to readers to discuss the 1984 São Paulo Declaration (SPD) on Self-reliant Analysis and Planning was based on two hunches: (1) that in the intervening almost two decades, a large number of energy specialists would have entered the scene with new and interesting points of view on the topic; (2) that a number of new socio-economic and technical factors had emerged to influence the discourse. The extremely encouraging response to the invitation has proved both these hunches right. Even without a comprehensive campaign, 20 comments have been received before going to press and at least another 5 would have made it given another week or so. Without any deliberate planning, ESD has acted as a forum for energy professionals to discuss a topic of widespread concern. At the same time, the responses have identified a number of new developments that necessitate an amendment and/or extension of the original declaration. What follows below is a synthesis based on the responses and almost wholly consisting of excerpts[1] from them. The full text of the individual comments follows in Part II. In addition, the original text of ‘‘Invitation to join a discussion on self-reliance’’ with the appended ‘‘Declaration on Self-reliant Energy Analysis and Planning’’, published in Volume VI No. 2 of ESD, is reprinted here in full to enable readers to appreciate better the responses contained here.

151. Williams, Robert H., 2003: Toward Zero Emissions for Transportation Using Fossil Fuels. Proceedings of the VIII Biennial Asilomar Conference on Transportation, Energy, and Env Policy, Washington, DC, Tranportation Research Board, (ISBN: 0309085713), 61-103
     [ Abstract ]

     The hydrogen (H²) fuel cell is receiving considerable attention as the fuel and engine option of choice for the automobile in the long term. The world's major automakers are racing to develop the technology - a quest bolstered in early 2002 by the Bush Administration's announcement of Freedom CAR (Cooperative Automotive Research), a collaboration between U.S. automakers and the U.S. government aimed at developing fuel cell cars and the associated H² fuel infrastructure. A transition to H² as a major energy carrier alternative to gasoline and diesel fuel and the fuel cell as an alternative to the internal combustion engine would be very costly and would require many decades. So these technologies must offer benefits that exceed the huge costs involved. Yet the societal costs of a business-as-usual future in which the automobile continues to be dominated by hydrocarbon-fueled internal combustion engine vehicles (ICEVs) are also arguably huge. Concerns about oil supply insecurity, air pollution damages, and climate change motivate serious consideration of introducing H² as a transport fuel.

152. Williams, Robert H., 2003: Decarbonized Fossil Energy Carriers and Their Energy Technological Competitors. Proceedings of the Workshop on Carbon Capture and Storage of the IPCC, Saskatchewan, Canada, Energy Research Center of the Netherlands, http://www.princeton.edu/pei/energy/publications/texts/Williams_02_Decarbonized_Fossil.PDF, 119-135
     [ Abstract ]

     Stabilizing atmospheric CO₂ in the range 450 - 550 ppmv requires deep reductions in CO₂ emissions for both electricity generation and markets that use fuels directly. Fossil fuel decarbonization/ CO₂ storage is an important option for reducing emissions from the power sector, but there are alternative non-carbon-based electricity options that will be strong competitors in terms of cost. Because of land-use constraints, use of carbon-neutral biofuels alone will be inadequate to solve the climate problem in markets that use fuels directly, so that it will probably also be necessary to introduce H₂ as an energy carrier. Costs for H₂ from fossil fuels with storage of the separated CO₂ are likely to be far less than costs of making H₂ from water using carbon-free (renewable or nuclear) electricity or heat sources. Although CO₂ capture and storage associated with making H₂ via gasification of coal and other carbonaceous feedstocks offers one of the least-costly approaches to a climate-friendly energy future, H₂ will not be widely used as an energy carrier for at least two decades. Nevertheless, thus making H₂ to serve industrial markets can provide low-cost CO₂ for CO₂ storage demonstration projects, thereby playing an important near-term role in understanding better the prospects for coping with climate change via decarbonizing fossil fuels and CO₂ storage.

153. Williams, Robert H., and Eric Larson, 2003: A Comparison of Direct and Indirect Liquefaction Technologies for Making Fluid Fuels from Coal. Energy for Sustainable Development, VII(4), doi:10.1016/S0973-0826(08)60382-8 103-129
     [ Abstract ]

     Direct and indirect liquefaction technologies for making synthetic liquid fuels from coal are compared. It is shown that although direct liquefaction conversion processes might be more energy efficient, overall system efficiencies for direct and indirect liquefaction are typically comparable if end-use as well as production efficiencies are taken into account. It is shown that some synfuels derived via indirect liquefaction can outperform fuels derived from crude oil with regard to both air-pollutant and greenhouse-gas emissions, but direct liquefaction-derived synfuels cannot. Deployment now of some indirect liquefaction technologies could put coal on a track consistent with later addressing severe climate and other environmental constraints without having to abandon coal for energy, but deploying direct liquefaction technologies cannot. And finally, there are much stronger supporting technological infrastructures for indirect than for direct liquefaction technologies. Prospective costs in China for some indirect liquefaction-derived fuels are developed but not costs for direct liquefaction-based synfuels, because experience with the latter is inadequate for making meaningful cost projections. Especially promising is the outlook for the indirect liquefaction product dimethyl ether, a versatile and clean fuel that could probably be produced in China at costs competitive with crude oil-derived liquid fuels. An important finding is the potential for realizing, in the case of dimethyl ether, significant reductions in greenhouse gas emissions relative to crude oil-derived hydrocarbon fuels, even in the absence of an explicit climate change mitigation policy, when this fuel is co-produced with electricity. But this finding depends on the viability of underground storage of H₂S and CO₂ as an acid gas management strategy for synfuel production. Many ‘‘megascale’’ demonstration projects for underground CO₂ storage and H₂S/CO₂ co-storage, along with appropriate monitoring, modeling, and scientific experiments, in alternative geological contexts, are needed to verify this prospect. It is very likely that China has some of the least-costly CO₂ sources in the world for possible use in such demonstrations. It would be worthwhile to explore whether there are interesting prospective demonstration sites near one or more of these sources and to see if other countries might work with China in exploiting demonstration opportunities at such sites.

154. Galloway, J. N., E. B. Cowling, S. P. Seitzinger, and Robert H. Socolow, March 2002: Reactive Nitrogen: Too Much of a Good Thing? Special Issue of Ambio:Optimizing Nitrogen Management in Food & Energy Productions, & Env Change, http://ambio.allenpress.com/archive/0044-7447/31/2/pdf/i0044-7447-31-2-60.pdf, 31(2), 60-63
     [ Abstract ]

     The 14^th element of the periodic table was named ‘nitrogene’ by Jean Claude Chaptal in 1790 (1). Two centuries later, the role of nitrogen (N) in biogeochemical processes and its critical function as a necessary nutrient are well understood. We know that humans (and plants and animals) require N to survive. We know that the abundant supply of gaseous dinitrogen (N₂) in the atmosphere is in a chemical form that plants and animals cannot use directly. We know that only a few special microorganisms can transform (“fix”) atmospheric nitrogen into reactive nitrogen (Nr) (2) that plants and animals can use. We know that another small group of microorganisms can transform (denitrify) Nr back to N₂. Based on the constancy of the N₂O record, we know that N fixation and denitrification in pre-industrial times were approximately equal (3).
     We also know that since the early 20th century, the amount of N fixed by unmanaged ecosystems has not been sufficient to meet human dietary needs. Fortunately, early in this period F. Haber and C. Bosch developed a process to tap the almost unlimited supply of nonreactive-N that exists in the atmosphere (1). This Haber-Bosch process made it possible to manufacture the Nr needed to meet the growing world food and fiber demand. Just as nitrogen is critical in human nutrition, it is also critical for all other plants and animals, from phytoplankton to elephants. The structure of whole ecosystems also is determined by Nr availability (4). As a result, Nr releases from food and energy production have the potential for significant unintended detrimental impacts on human health and both natural and managed ecosystems.
     Globally, humans currently ingest ~ 20 Tg N yr^–1 in their food. All of this Nr enters the environment. The resulting environmental consequences are magnified substantially, however, because an additional ~ 100 Tg N yr^–1 that was involved in food production, but never entered human mouths, also was released to the environment. In addition to this total of ~ 120 Tg N yr^–1, another ~ 25 Tg N yr^–1 of Nr was created by fossil fuel combustion, and still another ~ 20 Tg N yr^–1 was created for other uses by the Haber-Bosch process, for a total of ~ 165 Tg N yr^–1. This amount is about twice the amount of reactive N created by biological nitrogen fixation (BNF) in natural terrestrial ecosystems (~ 90 Tg N y^–1) (5).
     There is substantial regional variability in creation of Nr, its distribution, and its effects. Nr creation in Europe (6) and the United States (7) is dominated by both food and energy production; per-capita Nr creation rates are ~ 100 kg N capita^–1 yr^–1 and ~ 40 kg N capita–1 yr^–1, in North America and Europe, respectively. In Asia (8),
     although total Nr creation is larger than in Europe and North America combined, the per capita Nr creation rate is much less: ~ 17 kg N capita^–1 yr^–1 (5). In the future, while Nr creation in Europe and North America might decrease, it most certainly will increase in Asia due to demands for food and energy by a growing human population with an increasing per capita use of nitrogen (8). Both the contrast between Nr production by humans and nature, and the potential environmental consequences of Nr production, have been recognized for more than 30 years (9). During the last 4 years especially, increased international attention has been focused on the complexities of human alteration of the N cycle and on how to optimize the production of food and energy while minimizing environmental consequences.
     The First International Nitrogen Conference was held in March 1998 in The Netherlands. It documented the extent to which many of the world’s natural resources and environmental systems have been responding to Nr enrichment in recent decades (10). The Second International Nitrogen Conference was held in October 2001 in the USA and was attended by more than 400 participants from 30 countries on 6 continents. It provided a much-needed update on nitrogen science and policy 3 years after the First Conference. The Second Conference was designed to highlight policy relevant science. In addition, it provided an opportunity to focus on North America and to set the stage for a focus on Asia—the site of the Third International Nitrogen Conference in 2004.
     The primary objectives of the Second Conference were to: – Increase scientific knowledge about Nr sources and effects on people and the environment;
     – Stimulate communication among leaders involved in nitrogen production and consumption;
     – Explore balanced strategies to increase food and energy production while decreasing impacts on people and the environment, thereby making progress toward the general theme of the Conference: “Optimizing Nitrogen Management in Food and Energy Production and Environmental Protection”.
     The Second Conference produced 3 major products: i) A brief Conference Summary Statement (11); ii) the contributed papers of the Conference—130 peer-reviewed papers prepared by Conference participants and published in the The Scientific World in both electronic (12) and printed-book form (13); and iii) this AMBIO Special Issue on Reactive Nitrogen. This Issue is composed of 17 papers derived from the plenary presentations at the Conference. Most of the authors met for 2.5 days at the Erik Jonsson Center of the National Academy of Sciences in Woods Hole, Massachusetts in April 2001 to plan the integration of their diverse topics. Most papers were then distributed among the plenary authors prior to the Conference in October 2001. After the Conference, the papers were still further revised and improved in response to comments from other plenary authors, anonymous reviewers, and from us as editors.
     The remainder of this introductory paper summarizes scientific highlights and recommendations for decision-makers derived from the Second Conference. As outlined in the Table of Contents for this AMBIO Special Issue on Reactive Nitrogen, these 17 plenary papers provide outstanding summaries of Nr science and policy.

155. Kim, S.-R., 2002: Optimal Environmental Regulation in the Presence of Other Taxes: The Role of Non-Separable Preferences and Technology. The B.E. Journals in Economic Analysis & Policy, Berkeley Electronic Press, 1(1, Article 4),
     [ Abstract ]

     Recent studies find that environmental taxes typically exacerbate pre-existing tax distortions and, therefore, the optimal pollution tax should lie below the Pigouvian level (social marginal damages). This paper analyzes a general equilibrium model with non-separable preferences and technology, relatively rare assumptions in this literature, and finds that the second-best optimal pollution tax can be above or below the first-best Pigouvian level. Surprisingly, the ordering of the two does not depend on the degree of pre-existing tax distortion. Moreover, it depends not just on the difference between the two goods’ cross-price elasticities with leisure, but on that difference compared to the elasticity of demand for the polluting intermediate input. Finally, the paper shows that under plausible parameter conditions, a greater pre-existing tax distortion can increase the optimal level of environmental regulation.

156. Kreutz, Thomas, Robert H. Williams, Robert H. Socolow, P. Chiesa, and G. G. Lozza, September 2002: Production of Hydrogen and Electricity from Coal with CO₂ Capture. Proceedings of the 6th International Conference on Greenhouse Gas Control Technologies (GHGT-6), http://www.princeton.edu/pei/energy/publications/texts/Kreutz_Kyoto_02.pdf,
     [ Abstract ]

     This paper summarizes a series of studies examining the prospective performance and cost of facilities that convert coal to H₂, co-product electricity and a stream of concentrated CO₂ (for sequestration). Synthe-sis gas is produced via oxygen-blown, entrained flow coal gasification, quench cooled and shifted to (pri-marily) H₂ and CO₂ via sulfur-tolerant water-gas shift (WGS) reactors. Our focus is on separating H₂ from the syngas and processing the carbon-bearing raffinate/purge gas to produce electricity and CO₂. We explore the use of novel inorganic membrane reactors for H₂ separation and compare their performance and cost with conventional gas separation technologies: CO₂ capture via solvent absorption followed by H₂ purification using pressure swing adsorption (PSA). This work highlights potential economic benefits of high system pressure, low H₂ purity, and co-sequestering CO₂ with sulfur-bearing waste gases, H₂S and SO₂.

157. O'Neill, B., and Michael Oppenheimer, 2002: Climate change - Dangerous climate impacts and the Kyoto protocol. Science, 296, doi:10.1126/science.1071238 1971-1972
     [ Abstract ]

     Defining a long-term goal for climate change policy remains a critical international challenge. Article 2 of the UN Framework Convention on Climate Change defines the long-term objective of that agreement as stabilization of greenhouse gas concentrations at a level that avoids “dangerous anthropogenic interference” with the climate system. “Dangerous interference” can be viewed from a variety of perspectives, and the choice will ultimately involve a mixture of scientific, economic, political, ethical, and cultural considerations, among others (1). In addition, the links among emissions, greenhouse gas concentrations, climate change, and impacts are uncertain. Furthermore, what might be considered dangerous could change over time. However, both proponents and detractors of the Kyoto Protocol, which was designed as an initial step to implement the Framework Convention, have begun to demand a definition of long-term objectives. For example, on 11 June 2001, U.S. President George W. Bush stated that the emissions targets embodied in the Kyoto Protocol “were arbitrary and not based upon science” and “no one can say with any certainty what constitutes a dangerous level of warming, and therefore what level must be avoided.” Here, we propose several plausible interpretations of dangerous interference in terms of particular environmental outcomes (2) and examine the consistency between the Kyoto Protocol and emissions changes over time that would avoid these outcomes. Although the emissions limits required by the Kyoto Protocol would reduce warming only marginally (3), we show that the accord provides a first step that may be necessary for avoiding dangerous interference.

158. Oppenheimer, Michael, 2002: Book Review - Jeremy Leffett, The Carbon War: Global Warming and the End of the Oil Era. Climatic Change, 54(4), doi:10.1023/A:1016135402292 497-505
     [ Abstract ]

     Jeremy Leggett: 2000, The Carbon War: Global Warming and the End of the Oil Era, Penguin Books, 342 pp., ISBN 0-14-028494-X
     With the U.S. government rejecting further consideration of the Kyoto Protocol and the EU and other countries moving toward its ratification, it is far too early to write the definitive political history of the global warming problem. The public policy issue named Global Warming or Climate Change has many moving parts, with each at a different stage of development. Much is known about the geophysical and technological aspects of the issue and rather less about its biological and economic implications. Tomes have been written on each aspect, most notably the reports of the Intergovernmental Panel on Climate Change (IPCC).
     However, on the political and diplomatic aspects of the issue, the literature, as voluminous as it is, leaves much to be desired. There are lots of questions and not enough credible answers. Is the UN Framework Convention on Climate Change a noble but ultimately toothless statement of purpose or a set of visionary principles? Is the Kyoto Protocol the first step on a long road or a time-consuming detour? Are the European countries heroes or hypocrites for savaging the U.S.’s demurral on Kyoto? What about the myriad technologies, policies, and mechanisms for abating greenhouse gases and their consequences, including emission taxes, emission trading, solar energy, nuclear energy, energy efficiency, sinks, geo-engineering, natural gas, and so on? What will work outside the think tanks in the real world of politics and people? Most important of all, when, if ever, will the developing countries agree to emissions limitation?
     Have you been hammering your head against the wall on one side of this issue or another for longer than you care to remember? Have you had enough of the details? Do you want to relax with a good book? Allow me to recommend The Carbon War by Jeremy Leggett. Dr. Leggett, former oil geologist and former Greenpeace campaigner, is currently a solar energy entrepreneur. Leggett had a bright idea. By proselytizing insurance companies and other firms in the financial sector about the damage to insured property in a progressively less-predictable and potentially more-violent climate, he would try to convince them to lobby in favor of greenhouse gas reductions while altering their investment portfolios to favor solar energy. The Carbon War is a diary of those efforts. As in most interesting stories, there

159. Socolow, Robert H., 2002: The Century-Long Challenge of Fossil-Carbon Sequestration. U.S. Policy on Climate Change: What Next?, The Aspen Institute, Washington, D.C., http://www.princeton.edu/mae/people/faculty/socolow/century-long.pdf, 97-107
     [ Abstract ]

     The time scale of the Greenhouse problem is a century. This is an unfamiliar time scale for political action.
     The Greenhouse problem arises if the global energy system is dominated by fossil fuels throughout this century. Such dominance is likely. But there is a fossil-fuel-based solution. It is conceivable that most of the carbon in the next hundred years of fossil fuels can be prevented from reaching (can be "sequestered" from) the atmosphere.
     Fossil-carbon sequestration is conceptually entirely different from biological-carbon sequestration, yet, unfortunately, both kinds of sequestration are usually called, simply, "sequestration." Biological carbon sequestration removes carbon from the atmosphere.
     The politics of fossil-carbon sequestration are unlike the politics of carbon management strategies designed to bring the fossil fuel era to a rapid close. The fossil fuel industries are willing participants, and they are showing leadership. So are many countries and portions of countries rich in fossil fuel resources The result should be new coalitions supportive of policies intended to mitigate climate change.

160. Williams, Robert H., 2002: Facilitating Widespread Deployment of Wind and Photovoltaic Technologies. 2001 Annual Report of the Energy Foundation, www.ef.org, http://www.ef.org/documents/WilliamsEssayFinal.pdf, 19-30
     [ Abstract ]

     At the global level, installed wind capacity has grown an average of 25 percent per year since 1990; by the end of 2000 it had reached 17.0 gigawatts of electrical capacity (GWe) and was generating about 0.24 percent of electricity worldwide. In the United States, average wind power prices (in 2000 dollars) fell from 47 cents per kilowatt-hour (kWh) in 1981 to 5.1 cents/kWh in 1995, as installed wind-power capacity expanded to about 1.5 GWe. For many large new wind farms in the United States, unsubsidized 30-year levelized life-cycle costs are currently about 5 cents/kWh-and less than 4 cents/kWh in areas of high average wind speeds. Wind-power costs are expected to decline further as the industry gains experience, learns to exploit economies of scale both by using turbines with larger unit capacities and by building larger wind farms (more turbines per farm), sees reductions in project financing costs as developers and financial institutions gain confidence in the technology and its market prospects, and makes technological improvements (e.g., higher hubs to exploit the stronger winds aloft, materials that lower maintenance costs).

161. Goldenberg, J., T. B. Johansson, A.K.N. Reddy, and Robert H. Williams, 2001: Energy for the New Millenium. Ambio, 30(6), doi:10.1579/0044-7447-30.6.330 330-337
     [ Abstract ]

     The evolution of thinking about energy is discussed. When the authors began collaborating 20 years ago, energy was typically considered from a growth oriented, supply-side perspective, with a focus on consumption trends and how to expand supplies to meet rising demand. They were deeply troubled by the environmental, security and equity implications of that approach. For instance, about two billion people lack access to affordable modern energy, seriously limiting their opportunities for a better life. And energy is a significant contributor to environmental problems, including indoor air pollution, urban air pollution, acidification, and global warming. The authors saw the need to evolve a different perspective in which energy is provided in ways that help solve such serious problems. They argued that energy must become an instrument for advancing sustainable development—economically viable, need-oriented, self reliant and environmentally sound development—and that the focus should be on the end uses of energy and the services that energy provides. Energy technological options that can help meet sustainable development goals are discussed. The necessity of developing and employing innovative technological solutions is stressed. The possibilities of technological leapfrogging that could enable developing countries to avoid repeating the mistakes of the industrialized countries is illustrated with a discussion of ethanol in Brazil. The role foreign direct investment might play in bringing advanced technologies to developing countries is highlighted. Near-and long-term strategies for rural energy are discussed. Finally, policy issues are considered for evolving the energy system so that it will be consistent with and supportive of sustainable development.

162. Keller, Klaus, R. D. Slater, Michael Bender, and R. M. Key, 2001: Possible biological or physical explanations for decadal scale trends in North Pacific nutrient concentrations and oxygen utilization. Deep Sea Research II, 49(103), doi:10.1016/S0967-0645(01)00106-0 345-362
     [ Abstract ]

     We analyze North Pacific GEOSECS (1970s) and WOCE (1990s) observations to examine potential decadal trends of the marine biological carbon pump. Nitrate concentrations {[NO₃]} and apparent oxygen utilization (AOU) decreased significantly in intermediate waters (by - 0.6 and - 2.9 μmol kg^-1; respectively, at σ_θ = 27.4 kg m^-3; corresponding to ≈ 1050 m). In shallow waters (above roughly 750 m) [NO₃] and AOU increased, though the changes were not statistically significant. A sensitivity study with an ocean general circulation model indicates that reasonable perturbations of the biological carbon pump due to changes in export production or remineralization efficiency are insufficient to account for the intermediate water tracer trends. However, changes in water ventilation rates could explain the intermediate water tracer trends and would be consistent with trends of water age derived from radiocarbon. Trends in AOU and [NO₃] provide relatively poor constraints on decadal scale trends in the marine biological carbon pump for two reasons. First, most of the expected changes due to decadal scale perturbations of the marine biota occur in shallow waters, where the available data are typically too sparse to account for the strong spatial and temporal variability. Second, alternative explanations for the observed tracer trends (e.g., changes in the water ventilation rates) cannot be firmly rejected. Our data analysis does not disprove the null hypothesis of an unchanged biological carbon pump in the North Pacific.

163. Larson, Eric, Robert H. Williams, M. Regis, and L. V. Leal, 2001: A Review of Biomass Integrated-Gasifier/Gas Turbine Combined Cycle Technology and its Application in Sugarcane Industries, with an Analysis for Cuba. Energy for Sustainable Development, V(1), doi:10.1016/S0973-0826(09)60021-1 54-76
     [ Abstract ]

     Biomass integrated-gasifier/gas turbine combined cycle (BIG/GTCC) systems will be capable of producing up to twice as much electricity per unit of biomass consumed and are expected to have lower capital investment requirements per kW of capacity than condensing-extraction steam turbine (CEST) systems, the present-day commercial technology for electricity production from biomass. The significant levels of biomass available as by-products of sugarcane-processing offer a potentially attractive application for BIG/GTCC systems. We review BIG/GTCC designs and ongoing demonstration and commercial projects and present estimates of the performance of two different BIG/GTCC plant configurations integrated into sugar or sugar-and-ethanol factories. Because of the importance of operating a cogeneration facility the year round in order to achieve attractive economics, we present estimates of the availability of and collection cost for sugarcane trash (tops and leaves) as a fuel supplementary to bagasse. We present estimated costs for electricity generated by commercially mature BIG/GTCC systems using sugarcane-biomass for fuel in a Southeast Brazilian context. The electricity costs are prospectively competitive with CEST-generated electricity, which motivates our analysis of how many BIG/GTCC units might need building (and at what cost) in order to reduce capital costs to competitive levels. We conclude with an assessment of the potential impacts on the Cuban energy sector of the introduction of BIG/GTCC cogeneration systems in that country’s sugarcane industry. Cuba’s high per-capita production of sugarcane and its heavy dependence on oil for energy provide attractive conditions for a large-scale energy-from-sugarcane program.

164. Oppenheimer, Michael, et al., 2001: Technical Summary and Summary for Policy Makers. Climate Change 2001: The Science of Climate Change. 3rd Assessment Report of the IPCC, Cambridge University Press,
     [ Abstract ]

     Climate Change 2001: The Scientific Basis is the most comprehensive and up-to-date scientific assessment of past, present and future climate change. The report:
     • Analyses an enormous body of observations of all parts of the climate system. • Catalogues increasing concentrations of atmospheric greenhouse gases. • Assesses our understanding of the processes and feedbacks which govern the climate system. • Projects scenarios of future climate change using a wide range of models of future emissions of greenhouse gases and aerosols. • Makes a detailed study of whether a human influence on climate can be identified. • Suggests gaps in information and understanding that remain in our knowledge of climate change and how these might be addressed. Simply put, this latest assessment of the IPCC will again form the standard scientific reference for all those concerned with climate change and its consequences, including students and researchers in environmental science, meteorology, climatology, biology, ecology and atmospheric chemistry, and policymakers in governments and industry worldwide. J.T.

165. Socolow, Robert H., 2001: Scale, Awareness, and Conscience: The Moral Terrain of Ecological Vulnerability. New Dimensions in Bioethics, Norwell, MA, A. W. Galston and E. G. Schurr, eds., Kluwer Academic Publishers, (ISBN: 0792372492), 65-78
     [ Abstract ]

     Prosperity is stressing the environment. This interaction can be illuminated by separating out aggregate size (scale) available science (awareness), and the obligation to respond (conscience). Solutions require an evolving vision of the good life, a sustained commitment to open science, and both an active and reverent management of the Earth.

166. Socolow, Robert H., et al., 2001: An Assessment of the Department of Energy’s Office of Fusion Energy Sciences Program (contributor). Fusion Science Assessment Committee, Washington, D.C., National Academy Press, (ISBN: 10:0-309-07345),
     [ Abstract ]

     The purpose of this assessment of the fusion energy sciences program of the Department of Energy's (DOE's) Office of Science is to evaluate the quality of the research program and to provide guidance for the future program strategy aimed at strengthening the research component of the program. The committee focused its review of the fusion program on magnetic confinement, or magnetic fusion energy (MFE), and touched only briefly on intertial fusion energy (IFE), because MFE_relevant research accounts for roughly 95 percent of the funding in the Office of Science's fusion program. Unless otherwise noted, all references to fusion in this report should be assumed to refer to magnetic fusion.

167. Williams, Robert H., 2001: Addressing Challenges to Sustainable Development with Innovative Energy Technologies in a Competitive Electric Industry. Energy for Sustainable Development, V(2), doi:10.1016/S0973-0826(08)60269-0 48-73
     [ Abstract ]

     Radical change in the energy system is essential in the decades immediately ahead in order to address effectively the multiple economic, social, environmental, and insecurity challenges posed by conventional energy. This can come about only through a concerted international effort to speed up the rate of technological innovation worldwide for technologies that offer promise in addressing sustainable development objectives – with particular attention given to developing countries, which account for much of the world’s energy demand growth and where problems posed by conventional energy are severe. The effort should be aimed at channeling some of the enormous private-sector financial and technological resources to the development and widespread deployment of such new energy technologies. In the industrialized countries, public policies supportive of innovation directed to the needs of the developing world as well as domestic needs are called for. Developing country governments should strive to make their countries favorable theaters for energy technological innovation that is supportive of their development needs. There is a need to complement such national policy measures with establishment at the multilateral level of a framework for channeling vast private-sector financial resources to this process, with emphasis on developing countries. Either new multilateral institutions should be created to carry out the needed activities or some existing institutions might be transformed to take on these new responsibilities. It is suggested that if the latter approach is taken, the Global Environment Facility might be given this responsibility. The ongoing process of reform to improve the economic efficiency of electricity markets can assist the needed transition to the needed new energy technologies – if reforms include measures to promote energy technological innovation in ways that would serve sustainable development objectives. The combination of rapid energy demand growth plus environmental and energy market reforms could potentially transform developing country energy markets into favorable theaters for energy technological innovation. Under these conditions, developing country governments would have considerable market power to direct the course of this innovation – including the power to induce the private sector to provide those new energy technologies that they believe are well-suited to their development needs. With large internal markets, large rapidly industrializing countries in particular have an opportunity to become market leaders for selected sustainable energy technologies, with eventual export capability. It is desirable to put the needed innovation policies in place soon. Fundamental policy changes such as those proposed are typically easier to introduce when institutions are in ferment, as is the case with ongoing power sector reforms. Once power sector reforms have been put into place the policy arena will become quiescent, and it will be more difficult to bring about fundamental change.

168. Williams, Robert H., 2001: Toward Zero Emissions from Coal in China. Energy for Sustainable Development, V(4), doi:10.1016/S0973-0826(08)60285-9 39-65
     [ Abstract ]

     China depends for most of its energy on coal – a situation that is likely to persist in the light of the abundance of its coal resources, the paucity of its oil and gas resources, and the reluctance of the government to allow China to become overly dependent on energy imports. The challenge is to find ways to use coal without the enormous air pollution damage caused by current conversion technologies and with greatly reduced carbon dioxide (CO₂) emissions. A coal energy system for China is proposed that could ultimately be characterized by near-zero emissions of both air pollutants and greenhouse gases. The key enabling technology is oxygen-blown (O₂–blown) gasification to generate synthesis gas from coal. This technology is used in commercially ready integrated gasification combined-cycle power plants that can provide electricity with air pollutant emissions as low as emission levels for natural gas combined-cycle plants. O₂-blown gasification is not yet used in China’s energy sector, although the technology is well-established in China’s chemical process industry. The key enabling strategy, which would often lead to attractive energy costs without further technological advances, is “polygeneration” – the co-production from synthesis gas of at least electricity and one or more clean synthetic fuels (e.g., dimethyl ether (DME), Fischer-Tropsch (F-T) liquids, hydrogen (H₂) and often also chemicals, town gas, and/or industrial process heat. The products of polygeneration could be used in the near term to serve a wide range of energy needs with extremely low levels of air pollutant emissions. In such polygeneration configurations CO₂ can often be produced in relatively pure streams as a co-product as a result of processing to increase the synthetic fuel’s hydrogen-to-carbon ratio. In the near term this CO₂ might be used profitably for enhanced oil recovery or enhanced recovery of methane from deep beds of unminable coal where resource recovery opportunities exist. For the longer term the potential exists for evolving the coal energy system to the co-production primarily of electricity and H₂ for serving urban areas, with most of the carbon in the coal ending up as CO₂ that is sequestered in geological reservoirs such as in depleted oil and natural gas fields and deep saline aquifers at low incremental cost – even where there are no opportunities for using the CO₂ for enhanced resource recovery. The H₂ so produced would be used for fueling zero-polluting fuel-cell vehicles, for distributed cogeneration (combined heat and power) applications in stationary fuel cells, and for cooking and heating applications as well. A third clean carbon-based synthetic fuel might also be needed for serving rural markets that would be difficult to serve with H₂, unless there are breakthroughs in H₂ storage technology. DME is a strong candidate for becoming the “third” clean energy carrier for China. Evolving a coal-based energy system that would be characterized ultimately by near-zero emissions of air pollutants and greenhouse gases would probably involve shifting the center of gravity for central-station power generation to the chemical process industries that would ultimately be co-producing as their major products electricity, H₂, and (perhaps) DME. Ongoing structural reforms in the electric power sector that encourage greater competition in power generation would facilitate the realization of this vision for coal.

169. Williams, Robert H., 2001: Nuclear and Alternative Energy Supply Options for an Environmentally Constrained World: a Long-Term Perspective. Nuclear Power and the Spread of Nuclear Weapons: Can We Have One Without the Other?, Brassey's, Washington, DC, http://www.princeton.edu/~cmi/research/Capture/Papers/nuclear.pdf, 85-122
     [ Abstract ]

     Nuclear power is commercial technology that offers the potential for providing electricity with zero emissions of air pollutants and greenhouse gases. Despite this promise, the nuclear power industry is stagnating. Most energy projections show that, although some new capacity will be added (primarily in Asia) there will be little or no net growth or even a decline in nuclear generating capacity worldwide over the next two decades (Williams, 2000). Nuclear power faces four serious challenges: costs that are typically higher than for alternatives; concerns about reactor safety; the lack of significant progress in dealing with radioactive waste disposal; and the the nuclear weapons connection to nuclear power. The recent World Energy Assessment (WEA, 2000) reached judgments that there are good prospects for addressing the reactor safety challenge satisfactorily, and that the waste disposal problem can probably be solved technically—though it will be difficult to convince publics that the problem is soluble. No judgment was reached on the cost challenge ("the proof is in the pudding"). And the WEA expressed skepticism regarding the prospects for coping effectively with the nuclear weapons connection to nuclear power. This skepticism is rooted in the formidable extent of the challenge of separating the peaceful atom from the military atom—especially at the high levels of nuclear power development needed to "make a dent" in climate change mitigation, as an alternative to continued reliance on fossil fuels over the longer term.

170. Ogden, J. M., Thomas Kreutz, and M. M. Steinbugler, 2000: Fuels For Fuel Cell Vehicles. Fuel Cells Bulletin, 3(16), doi:10.1016/S1464-2859(00)86613-4 5-13
     [ Abstract ]

     The issue of fuel choice impacts both fuel cell vehicle design and infrastructure development. In general, there is a trade-off between simpler vehicle design (hydrogen vehicles are inherently simpler than those with onboard fuel processors) and simpler infrastructure issues (liquid fuels such as gasoline or methanol are easier to store and handle, and are more compatible with the existing refueling infrastructure). In this article we compare fuel cell vehicle characteristics and infrastructure requirements for four possible fuel options: compressed hydrogen gas, methanol, gasoline and synthetic liquids derived from natural gas. The advantages and disadvantages of various fuels are discussed, and possible fuel strategies leading towards the commercialisation of fuel cell vehicles are explored.

171. Socolow, Robert H., May 1999: Nitrogen management and the future of food: Lessons from the management of energy and carbon. Proceedings of the National Academy of Sciences of the United States of America, http://www.pnas.org/content/96/11/6001.full.pdf, 6001-6008
     [ Abstract ]

     The food system dominates anthropogenic disruption of the nitrogen cycle by generating excess fixed nitrogen. Excess fixed nitrogen, in various guises, augments the greenhouse effect, diminishes stratospheric ozone, promotes smog, contaminates drinking water, acidifies rain, eutrophies bays and estuaries, and stresses ecosystems. Yet, to date, regulatory efforts to limit these disruptions largely ignore the food system. There are many parallels between food and energy. Food is to nitrogen as energy is to carbon. Nitrogen fertilizer is analogous to fossil fuel. Organic agriculture and agricultural biotechnology play roles analogous to renewable energy and nuclear power in political discourse. Nutrition research resembles energy end-use analysis. Meat is the electricity of food. As the agriculture and food system evolves to contain its impacts on the nitrogen cycle, several lessons can be extracted from energy and carbon: (i) set the goal of ecosystem stabilization; (ii) search the entire production and consumption system (grain, livestock, food distribution, and diet) for opportunities to improve efficiency; (iii) implement cap-and-trade systems for fixed nitrogen; (iv) expand research at the intersection of agriculture and ecology, and (v) focus on the food choices of the prosperous. There are important nitrogen-carbon links. The global increase in fixed nitrogen may be fertilizing the Earth, transferring significant amounts of carbon from the atmosphere to the biosphere, and mitigating global warming. A modern biofuels industry someday may produce biofuels from crop residues or dedicated energy crops, reducing the rate of fossil fuel use, while losses of nitrogen and other nutrients are minimized.

172. Socolow, Robert H., and V. Thomas, 1997: The Industrial Ecology of Lead and Electric Vehicles. Journal of Industrial Ecology, Cambridge, MA, MIT Press, 1(1), doi:10.1162/jiec.1997.1.1.13 13-36
     [ Abstract ]

     The lead battery has the potential to become one of the first examples of a hazardous product managed in an environmentally acceptable fashion. The tools of industrial ecology are helpful in identifying the key criteria that an ideal lead-battery recycling system must meet maximal recovery of batteries after use, minimal export of used batteries to countries where environmental controls are weak, minimal impact on the health of communities near lead processing facilities, and maximal worker protection from lead exposure in these facilities. A well-known risk analysis of electric vehicles is misguided, because it treats lead batteries and lead additives in gasoline on the same footing and implies that the lead battery should be abandoned. The use of lead additives in gasoline is a dissipative use where emissions cannot be confined: the goal of management should be and has been to phase out this use. The use of lead in batteries is a recyclable use, because the lead remains confined during cycles of discharge and recharge. Here, the goal should be clean recycling. The likelihood that the lead battery will provide peaking power for several kinds of hybrid vehicles-a role only recently identified increases the importance of understanding the levels of performance achieved and achievable in battery recycling. A management system closely approaching clean recycling should be achievable.

173. Baehr, J., Klaus Keller, and J. Marotzke, 0000: Detecting potential changes in the meridional overturning circulation at 26°N in the Atlantic. Climatic Change, doi:10.1007/s10584-006-9153-z
     [ Abstract ]

     We analyze the ability of an oceanic monitoring array to detect potential changes in the North Atlantic meridional overturning circulation (MOC). The observing array is ‘deployed’ into a numerical model (ECHAM5/MPI-OM), and simulates the measurements of density and wind stress at 26°N in the Atlantic. The simulated array mimics the continuous monitoring system deployed in the framework of the UK Rapid Climate Change program. We analyze a set of three realizations of a climate change scenario (IPCC A1B), in which – within the considered time-horizon of 200 years – the MOC weakens, but does not collapse. For the detection analysis, we assume that the natural variability of the MOC is known from an independent source, the control run. Our detection approach accounts for the effects of observation errors, infrequent observations, autocorrelated internal variability, and uncertainty in the initial conditions. Continuous observation with the simulated array for approximately 60 years yields a statistically significant (p < 0.05) detection with 95 percent reliability assuming a random observation error of 1 Sv (1 Sv = 10⁶ m³s⁻¹). Observing continuously with an observation error of 3 Sv yields a detection time of about 90 years (with 95 percent reliability). Repeated hydrographic transects every 5 years/ 20 years result in a detection time of about 90 years/120 years, with 95 percent reliability and an assumed observation error of 3 Sv. An observation error of 3 Sv (one standard deviation) is a plausible estimate of the observation error associated with the RAPID UK 26°N array.

174. Liu, Guangjian, Eric Larson, Robert H. Williams, and J. R. Katzer, in press: Gasoline from Coal and Biomass with CSS Performance and Cost Analysis. Proceedings of the 8th Annual Carbon Capture and Sequestration Conference, Pittsburgh, PA. 0/00.

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