CMI Integration introduces new conceptual frameworks that are useful for climate change policy, including efforts to make emerging statistical analyses of extreme events more accessible; improve the risk-assessment framework for the current scientific understanding of sea level rise; and expand discussions of climate change mitigation and adaptation from global-scale intervention to small-scale urban planning and engineering. In addition, there is new work on the limited potential for carbon dioxide (CO2) reuse after capture and chemical activation.
Research Highlights – At a Glance
Michael Oppenheimer: Cities are engineered landscapes, and planning and development choices can significantly exacerbate or mitigate the impacts of climate and environmental change. The height of buildings and their spatial configuration influence the urban form and surface texture, which further affect the surface aerodynamic processes, energy use efficiency and emissions. A “smart” engineered urban landscape can reduce heat stress, and improve energy efficiency and air quality.
Robert Williams, Eric Larson, and Thomas Kreutz: Collaborating with analysts at NRG Energy, the largest competitive power producer in the US, the Energy Systems Analysis Group (ESAG) launched a new initiative in 2016 to model the prospective evolution of high penetrations of intermittent renewable electricity supplies (iRES – mainly wind and solar photovoltaic) on US grids. Major challenges must be addressed to reach high iRES penetrations cost-effectively. The research seeks to understand and articulate the cost and carbon implications to mid-century of deployment of various grid technologies interacting with alternative electricity and carbon market redesigns.
Robert Socolow: The widely discussed carbon mitigation strategy, CO2 capture and use, is often touted as a way to improve the use of fossil fuel carbon. The idea is to make vehicle fuel by chemically reducing the CO2 in the exhaust stream of a fossil fuel power plant, thereby using the carbon extracted with a fossil fuel twice—once for power and once for transport. This reasoning is flawed, because the same carbon benefit can almost always be achieved more straightforwardly and at lower cost by an alternate use of the large amount of low-carbon energy required to make fuel from CO2. Only a high oil price and a high price for electric vehicles can create a domain of competitiveness for CO2 capture and use.
Designing Urban Land Form for Climate and Environmental Co-
Principal Investigators: Michael Oppenheimer
At a Glance
Cities are engineered landscapes, and planning and development choices can significantly exacerbate or mitigate the impacts of climate and environmental change. The height of buildings and their spatial configuration influence the urban form and surface texture, which further affect the surface aerodynamic processes, energy use efficiency and emissions. A “smart” engineered urban landscape can reduce heat stress, and improve energy efficiency and air quality.
Heat stress associated with climate change is one of the most serious climate threats to human society. The impact is further amplified for urban populations because of the urban heat island effect—a common phenomenon in which surface temperatures are higher in urban areas than in surrounding rural areas. Cities are also hotspots for carbon dioxide emissions and strong sources of anthropogenic aerosols. Because more than 50% of the world’s population currently lives in cities, and that percentage is projected to increase to 70% by year 2050, there is a pressing need to find effective solutions to cope with the heat and environmental stress.
It is now recognized that in addition to the traditional emphasis on building up the city’s preparedness or resilience, urban planning and adaptation agendas should also include active modification to the urban landscape in the face of climate change1.
Figure 3.1.1. Schematic of air turbulence over urban surface.
In 2016, STEP postdoctoral fellow Lei Zhao, with his advisor, Michael Oppenheimer, developed a novel methodology that combined government building footprint dataset, ultra-high resolution imagery from LiDAR, and satellite observations to investigate the impact of surface morphology and texture on urban climate and environment2. The results point to robust relationships between urban morphological properties and the efficiency of heat convection from the city’s surface to the lower atmosphere. Specifically, the height of buildings and their spatial configuration are strong determinants of surface aerodynamic roughness, which represents the urban convection efficiency (Figure 3.1.1.). Intensified convection helps not only to reduce temperatures but also to disperse air pollutants.
The study has three important implications. First, this work for the first time demonstrates that surface morphology can affect the urban local climate and environment. Further, it advances the scientific understanding of the impacts of complex surfaces on surface aerodynamic processes. In climate models, land surface is usually modeled as a grid of “tiles” that represent surfaces such as vegetated land, glacier, wetland, lake, and urban areas (Figure 3.1.2.). For urban tiles, however, surface geometry, representation, and parameterization are still highly simplified. Insights generated from this study will help improve the ability of climate models to accurately quantify the surface energy, momentum and mass transfer between land and the atmosphere over these urban tiles.
Figure 3.1.2. Schematic of land surface tiles used in climate models.
Second, the study provides actionable guidance to policy makers on future urban planning and development concerning urban heat mitigation, climate change adaptation and air pollution abatement. Cities are engineered landscapes, and planning and development choices can significantly exacerbate or mitigate the impacts of climate and environmental change. Results from this study point to the possibility of “smart” engineering urban landscapes to reduce heat stress, and improve energy efficiency and air quality.
Third, it bridges a disconnect in the global climate research agenda between large-scale carbon mitigation and local-scale urban engineering. Unlike planetary-scale mitigation strategies, urban engineering has impacts on a much smaller area of land. Cities are functional units of climate mitigation agendas. A reorientation of some of the discussion of climate change mitigation and adaptation from global-scale climate intervention to small-scale urban planning and engineering can motivate local actions by delivering environmental benefits directly and immediately.
1 Zhao, L., X. Lee, and N.M. Schultz, 2017. A wedge strategy for mitigation of urban warming in future climate scenarios. Atmos. Chem. Phys. Discuss., in review. doi:10.5194/acp-2016-1046.
2 Zhao, L., M. Oppenheimer, Q. Li, Q. Zhu, and N.M. Schultz, 2017. Designing built-up morphology for urban climate and environmental co-benefits, in preparation.
Understanding Challenges with Intermittent Renewable Electricity Expansion
Principal Investigator: Tom Kreutz, Eric Larson, and Bob Williams
At a Glance
Collaborating with analysts at NRG Energy, the largest competitive power producer in the US, the Energy Systems Analysis Group (ESAG) launched a new initiative in 2016 to model the prospective evolution of high penetrations of intermittent renewable electricity supplies (iRES – mainly wind and solar photovoltaic) on US grids. Major challenges must be addressed to reach high iRES penetrations cost-effectively. The research seeks to understand and articulate the cost and carbon implications to mid-century of deployment of various grid technologies interacting with alternative electricity and carbon market redesigns.
Incentives from governments around the world have led to rapid growth in iRES while R&D and experience have led to dramatic reductions in their capital costs—trends that are expected to continue. There are at least three major challenges to be understood and addressed to realize high iRES penetrations.
One major challenge is providing electric balancing capacity in the form of backup or storage. This challenge is well-addressed today by natural gas-fired combustion turbine (CT) and combined cycle (GTCC) backup units, together with iRES curtailment whenever iRES exceed demand. However, as iRES grid penetration increases, iRES generation costs will rise despite falling capital costs, because such curtailments will increase rapidly. California might be considered a window to the future of iRES. Under the state’s new 50% Renewable Portfolio Standard (RPS) mandate, iRES is expected to reach 35% of total generation by 20301. Figure 3.2.1. illustrates the iRES over-generation problem for California, where future iRES is expected to be dominated by utility-scale solar photovoltaic electricity.
Figure 3.2.1. Modeled base-case electricity generation for a day in April 2030 for the California independent system operator (CAISO) grid with different RPS requirements and absent new bulk electricity storage1. To satisfy the 50% RPS, about 20 GW of PV generation (the over-generation rate, in red) would need to be curtailed at mid-day.
High iRES grids dominated by either wind or solar are likely to require high iRES curtailment rates, although for wind, the iRES supply pattern will be less predictable, over-generation will take place at different times of day, and required ramping rates for balancing capacity will typically be faster. Figure 3.2.2. illustrates these features for Texas, which currently has by far the largest wind generating capacity of any US state (18.5 GW): wind power output (a) is typically strongest at night, (b) drops sharply in the morning as load is rising, (c) picks up again in the evening as load begins to drop, and (d) varies significantly day by day (also season by season).
Figure 3.2.2. Seven days of wind power output and electric load for the grid operated by the Electric Reliability Council of Texas (ERCOT)2. Net system load is calculated as gross load minus wind generation.
In both solar-dominated and wind-dominated iRES cases, the mismatch between iRES and load means that the system operator needs to curtail over-generated iRES at times and to rapidly adjust backup supplies at other times in order to reliably satisfy electricity demand. Grids with high iRES made up of a more balanced mix of solar and wind are likely to have lower curtailment rates, partly because wind and sun may be available at different times.
Curtailments of iRES can also be mitigated by storing over-generated electricity. Bulk electricity storage via batteries over periods longer than a couple of hours is expensive3, and pumped hydro storage (PHS) is geographically constrained. However, natural gas-fired compressed air energy storage (CAES) is likely to be less costly than PHS and potentially deployable throughout most of the US4. CAES is commercially ready for storage in salt caverns (deployable in wind-rich regions such as Texas and possibly also the Rocky Mountain and northern Great Plains regions5) and might be cost-competitive with new CT backup capacity6. CAES could be much more widely available via storage in porous media (expected to be less costly than salt caverns4) and mined hard rock—options that have not yet been demonstrated.
A second major challenge to high iRES penetrations is the reduction in carbon dioxide (CO2) emissions from balancing capacity that likely will be required to meet long-term carbon-mitigation goals. This can be accomplished via some mix of electricity storage (including natural gas CAES) and Carbon Capture and Storage (CCS). The latter is challenging because of high costs for CCS-integrated balancing capacity units that have to operate at low capacity factors, as will be the case with high iRES grid penetrations. Plausible strategies for addressing this challenge effectively have been proposed7.
A third major challenge is that increasing penetrations of iRES threaten the effective functioning of wholesale electricity markets, in which the price paid to all generators is set by the operating cost of the marginal unit. Because the operating cost of iRES is close to zero, large iRES penetrations significantly depress the prices paid to all generators, even those that play critical balancing roles and others with desirable features such as low carbon emissions. Continuing traditional short-run marginal cost-based pricing of wholesale electricity in the face of continuing iRES penetrations threatens new investments of any kind needed to maintain a reliable grid, including investments needed to realize deep decarbonization goals. Brouwer, et al. 8 demonstrate how traditional marginal-cost electricity pricing is increasingly untenable as iRES penetrations grow (Figure 3.2.3). New policies that adequately reward generators for critical attributes like low-carbon emissions and balancing capabilities are needed to resolve this dilemma.
Figure 3.2.3. Alternative low-carbon electricity scenarios for Western Europe in 20508 illustrating the problem with short-run marginal cost pricing of wholesale electricity as penetrations of iRES increase. The cost of electricity supply (black line, right axis) is higher than the market price paid for electricity based on marginal-cost pricing (red line), and the gap grows with level of iRES penetration. Each bar shows the lowest annual system cost in 2050 (left axis) for the assumed iRES penetration and short-run marginal-cost-based dispatching. Each scenario meets exogenous system reliability and CO2 emissions constraints (96% lower than in 1990). The CO2 emission price in the scenario with 0% iRES is 165 €/t, the price needed to induce the needed investments in non-iRES low-carbon options. In the other scenarios, a 70 €/t price is applied, the value that induces investment in a natural gas combined cycle with CCS.
ESAG continues to build a relationship with analysts at NRG Energy and is working with them to conceptualize a modeling framework for analyzing the impacts that different grid technologies and electricity-market redesigns would have on achieving iRES penetration and carbon-mitigation goals. Models used by others can be loosely classified as capacity expansion, which typically examine impacts of alternative policies on mid-to-long term generation mixes, but without considering economic dispatch competition and associated wholesale-electricity market structures9; or unit commitment-dispatch which are typically designed to simulate day-by-day, hour-by-hour economic dispatching for a geographically-specified power grid10. Both types of models require large numbers of inputs and considerable computation times, making them unwieldy for exploring multiple scenarios. ESAG seeks to develop a modeling framework that combines essential features of both model types, but maintains sufficient simplicity and nimbleness that alternative technology and policy scenarios can be studied with manageable computation times.
1 Energy + Environmental Economics, 2014. Investigating a Higher Renewables Portfolio Standard in California, final report of a study sponsored by the Los Angeles Department of Water and Power, Pacific Gas and Electricity Company, Sacramento Municipal Utilities District, San Diego Gas and Electric Company, and Southern California Edison Company.
2 Electric Reliability Council of Texas, 2017. Hourly Aggregated Wind Output, downloaded from ERCOT website, January 23, 2017.
3 Lazard, 2015. Lazard’s Levelized Cost of Storage Analysis – Version 1.0.
4 Electric Power Research Institute, 2008. Compressed Energy Storage Scoping Study for California, prepared for the California Energy Commission’s Public Interest Energy Program, CEC-500-2008- 069.
5 The only commercial CAES technology involves caverns solution-mined in salt domes, which are available in the Gulf Coast region of Texas. Such caverns could also be created in the bedded salt formations that are available in the Rocky Mountain and Northern Great Plains regions, although creating salt caverns in bedded salt is more challenging. (S. Succar and R.H. Williams, 2008. Compressed Air Energy Storage: Theory, Operation and Applications, a report of the Energy Systems Analysis Group prepared for BP, Princeton Environmental Institute, Princeton University.)
6 The specific capital cost ($/kWe) for a natural gas-fired salt-cavern CAES unit with 10 hours of storage is likely to be no higher than for a new CT, and the natural gas required per kWh is ~2/5 of that required for the CT unit4. The latter benefit will be offset to some degree by the cost paid for the IRE that will be stored.
7 Energy Technologies Institute, 2015. The Role of Hydrogen Storage in a Clean Responsive Power System.
8 Brouwer, A.S., M. van den Broek, W. Zappa, W.C. Turkenburg, and A. Faaij, 2016. Least-cost options for integrating renewables in low-carbon power systems. Appl. Energ., 161: 48-74. doi:10.1016/j. apenergy.2015.09.090.
9 Mai, T., R. Wiser, D. Sandor, G. Brinkman, G. Heath, P. Denholm, D.J. Hostick, N. Darghouth, A. Schlosser, and K. Strzepek, 2012. Exploration of High-Penetration Renewable Electricity Futures. In Renewable Electricity Futures, Vol. 1. NREL/TP-6A20-52409-1. National Renewable Energy Laboratory.
10 Simão, H.P., W.B. Powell, C.L. Archer, and W. Kempton, 2017. The challenge of integrating offshore wind power in the US electric grid. Part II: Simulation of electricity market operations. Renew. Energ., 103: 418-431.
11 Meerman, J.D., and E.D. Larson, 2017. Negative-carbon drop-in transport fuels produced via catalytic hydropyrolysis of woody biomass with CO2 capture and storage. Sustainable Energy Fuels, in review.
12 Larson, E.D., D. Tilman, C. Lehman, and R.H. Williams, 2016. Sustainable Transportation Energy with Net Negative Greenhouse Gas Emissions: an integrated ecological and engineering systems analysis. Progress report to Stanford University Global Climate and Energy Project, from the Energy Systems Analysis Group (Princeton) and Department of Ecology, Evolution, and Behavior (U. Minnesota).
13 Williams, R.H., 2016. Toward a “Marriage of CCS and IRE Technologies” in the Quest to Firm Up Intermittent Renewable Electricity with Bulk Balancing Capacity. White paper in review.
14 Williams, R.H., 2016. The Strategic Importance and Development Status of Porous Media CAES Technology. Addendum to the “Bulk Storage Capacity Is Key to Enabling High IRE Grid Penetration” section of Williams, R.H., 2016. In review.
The Limited Domain of Carbon Capture and Use
Principal Investigator: Robert Socolow
At a Glance
The widely discussed carbon mitigation strategy, carbon dioxide (CO2) capture and use, is often touted as a way to improve the use of fossil fuel carbon. The idea is to make vehicle fuel by chemically reducing the CO2in the exhaust stream of a fossil fuel power plant, thereby using the carbon extracted with a fossil fuel twice—once for power and once for transport. This reasoning is flawed, because the same carbon benefit can almost always be achieved more straightforwardly and at lower cost by an alternate use of the large amount of low-carbon energy required to make fuel from CO2. Only a high oil price and a high price for electric vehicles can create a domain of competitiveness for CO2capture and use.
A leading strategy for combatting climate change is CO2 capture and storage, or CCS. It is already deployed at a few coal power plants. The CO2 that results from combustion is captured with chemicals and sent into geological formations deep below ground for long-term storage. Upon hearing about CCS for the first time, laypeople and experts alike ask: If you go to the trouble of capturing CO2 at power plants, surely there is something better to do with it than to put it underground?
This is such a reasonable question! The strategy that is being sought even has a name: “Carbon Dioxide Capture and Use,” or CCU. Worldwide, chemists are seeking new ways to “activate” CO2 to make CCU more competitive. This Highlight explores the CCU economy. In the second half of 2016, I served on a task force that wrote a report for the US Department of Energy. Entitled “Task Force Report on CO2 Utilization and Negative Emissions Technologies,” it was submitted to Secretary of Energy, Ernest J. Moniz, on December 13, 2016. It is online at https://energy.gov/seab/downloads/final-reporttask-force-co2-utilization, where the task force participants and a DOE “Assessment” of the report are also found. This Highlight explores an issue that was left unresolved in our report. It is a work in progress.
Today’s economy and the CCU economy Figure 3.3. (top panel) shows a simplified representation of today’s fossil-fuel-based energy economy, as well as the CCU economy and two alternatives. In all panels, chemically reduced carbon is removed from the subsurface as fossil fuel (red arrow), oxidized to release the energy that powers the economy (rounded rectangle), and sent to the atmosphere as CO2 for disposal (blue arrow). The sketch separates today’s economy into two sub-economies, one where energy is used centrally and the other where energy is widely distributed before use.
In the CCU economy (upper-middle panel), the blue and red arrows in the top panel are unchanged, but the passage of carbon through the economy is more complex. CO2 is captured at a centralized facility after fossil fuel is burned, then chemically reduced to a synthetic fuel in a conversion facility with the help of low-carbon energy (green dashed arrow), and the synthetic fuel is burned at a decentralized energy conversion device (e.g., in a vehicle engine). Thus, there are two power plants: one provides the CO2 (the “source plant”) and the other enables the conversion of the CO2 into synthetic fuels (the “CCU-enabling plant”). In a transaction internal to CCU, the source plant pays a “tipping fee” to the conversion facility instead of paying the government a CO2 emissions tax or paying for CO2 storage. For specificity, imagine that in the CCU system wind power transforms coal-power-plant exhaust into gasoline. The circle represents the conversion process.
Figure 3.3. Carbon flows in today’s energy system (top) and three future low-carbon energy systems, all of which augment the role of low-carbon energy (dashed green arrow). These alternatives feature Carbon Capture and Use (CCU, upper middle), low-carbon centralized energy (lower middle), and low-carbon distributed energy use (bottom). Chemically reduced carbon is shown with red arrows and CO2 with blue arrows. In the CCU energy system, CO2 is captured at a centralized fossil-fuel-burning facility and transformed back to a hydrocarbon for a second, decentralized use. Not shown is the part of the CCU economy where uses of CO2 do not require its chemical transformation.
In the CCU economy (upper-middle panel), the blue and red arrows in the top panel are unchanged, but the passage of carbon through the economy is more complex. CO2 is captured at a centralized facility after fossil fuel is burned, then chemically reduced to a synthetic fuel in a conversion facility with the help of low-carbon energy (green dashed arrow), and the synthetic fuel is burned at a decentralized energy conversion device (e.g., in a vehicle engine). Thus, there are two power plants: one provides the CO2 (the “source plant”) and the other enables the conversion of the CO2 into synthetic fuels (the “CCU-enabling plant”). If the source of CO2 for CCU is a cement or steel plant, rather than a power plant, some of the arguments here are less strong, because substitution of a low-carbon alternative is less straightforward, given that carbon flows are associated not only with energy production but also with the industrial process. In a transaction internal to CCU, the source plant pays a “tipping fee” to the conversion facility instead of paying the government a CO2 emissions tax or paying for CO2 storage. For specificity, imagine that in the CCU system wind power transforms coal-power-plant exhaust into gasoline. The circle represents the conversion process.
Alas, CCU is a deeply flawed concept, primarily because there are nearly always better ways of using the low-carbon enabling energy.
Low-carbon enabling energy for CCU Somewhat more than one unit of enabling energy must be used to convert CO2 (and water) into one unit of high-value energy embedded in carbon-based liquid or gaseous fuel. How else could the enabling energy be used? Two limiting cases are presented in the lower-middle and bottom panels of Figure 3.3., respectively, where low-carbon energy substitutes exclusively for either centralized or distributed uses of fossil energy. Imagine that in the “Low- Carbon Power” system wind power enables the closing down of traditional coal plants, while the gasoline system remains unchanged. And imagine that the “Low-Carbon Vehicle” system is one where wind power enables electric vehicles, while coal power plants keep running.
All three options can become less costly than doing nothing when the CO2 price is high; the case for CCU rests on there being situations where CCU competes favorably with the other options. Comparing the CCU option and the Low-Carbon Vehicle option (bottom panel), there is a breakeven price for electric vehicles above which CCU synthetic fuels are competitive. CCU can prosper only when little progress has been made toward the electrification of vehicles and the use of biomass-derived fuel. Such a world rarely emerges in the low-carbon narratives embedded in today’s scenarios. Rather, the common view is that the electrification of decentralized energy, especially in transport, will flourish when a strong CO2 emissions constraint is imposed; sometimes, only air travel is not electrified by mid-century.
Comparing the CCU option and the Low-Carbon Power option (lower-middle panel), there is another breakeven price, the price of crude oil (and therefore crude-oil-derived vehicle fuels), above which CCU synthetic fuels are competitive. Thus, CCU requires both a high oil price and a high price for electric vehicles. Either constraint can be the one that limits the competitiveness of CCU. In a highly idealized schematic model, CCU must be less expensive than both (crude-oil fuel minus coal power) and (electric vehicles minus wind power).
CO2 capture cost We cannot neglect the substantial investment required to capture the CO2 at the source plant. In a circumstance particularly favorable to CCU, but surely a niche market, the source power plant has been a CCS plant, and thus has already paid the capture costs, but for some reason its access to storage has ended.
Delay time CCU is sometimes presented as a CO2 storage strategy. It is not. An important variable is the delay time: the length of time between the capture event at the source plant and the moment of CO2 emission when the CCU fuel is used. A delay time of several decades or longer can occur in principle, but only if the captured carbon becomes embedded in a long-lived product like a plastic bench or a steel pipe.
Enhanced oil recovery The CCU panel of Figure 3.3. represents only uses of CO2 where it is transformed chemically. CO2 chemically unchanged is used in the food system and for cleaning, but by far its largest use is in the oil industry for “enhanced oil recovery (EOR),” where CO2 is injected into old oil fields to promote the extraction of additional oil. Nearly all of the CO2 brought to the oil field for EOR remains there when oil production ceases, trapped in geological formations. EOR today leaves about one carbon atom behind in the oil field for each carbon atom in the produced oil.
EOR could be modified so that much more carbon is left behind. To the disappointment of the many champions of CO2 reuse as a pathway to hydrocarbons, EOR may be the only climate-significant version of CCU.
I particularly wish to thank Nate Lewis for his insistence that CCU was being overvalued and his patience while I struggled to make the argument my own. Along the way, exchanges especially with Arun Majumdar, but also with Sally Benson, Emily Carter, Mike Ramage, and Eric Toone, were essential.
Hailey, A.K., J.C. Meerman, E.D. Larson, and Y.-L. Loo, 2016. Low-carbon “drop-in replacement” transportation fuels from non-food biomass and natural gas. Appl. Energ., 183: 1722-1730. doi:10.1016/j. apenergy.2016.09.068.
Larson, E.D, C. Greig, Andlinger Center Energy Systems Analysis Group, and University of Queensland Energy Initiative, 2016. Design/Cost Study and Commercialization Analysis for Synthetic Jet Fuel Production at a Mississippi Site from Lignite and Woody Biomass with CO2 Capture and Storage via EOR, Milestone 3 Report: Summary of the Final Process Design. Under US DOE grant DE-FE0023697.
Larson, E.D., T. Kreutz, R. Williams, H. Meerman, and C. Greig. 2016. Design/Cost Study and Commercialization Analysis for Synthetic Jet Fuel Production at a Mississippi Site from Lignite and Woody Biomass with CO2 Capture and Storage via EOR, Milestone 4 Report: Summary of Financial Analysis for FOAK LBJ Plant and Prospective NOAK Commercial Plants. Under US DOE grant DE-FE0023697.
Meerman, J.D., and E.D. Larson, 2017. Negative-carbon drop-in transport fuels produced via catalytic hydropyrolysis of woody biomass with CO2 capture and storage. Sustainable Energy Fuels, in review.
Scovronick, N, M. Budolfson, F. Dennig, M. Fleurbaey, A. Siebert, R. Socolow, D. Spears, and F. Wagner, 2017. Impact of population growth and population ethics on climate change mitigation policy. Proc. Natl. Acad. Sci., in review.
Socolow, R.H., J.W. Baldwin, C.B. Chou, P.M. Hannam, J. Jhaveri, K. Keller, W. Peng, S. Rabin, A.P. Ravikumar, A.M. Trierweiler, and X.T. Wang, 2016. Fusion Energy Via Magnetic Confinement: An Energy Technology Distillate from the Andlinger Center for Energy and the Environment. http://acee.princeton.edu/distillates/ fusion-energy-via-magnetic-confinement/.
Socolow, R.H, Secretary of Energy Advisory Board Task Force Member, 2016. Task Force Report on CO2 Utilization and Negative Emissions Technologies, submitted to the US Department of Energy, December 13, 2016. https://energy.gov/seab/downloads/ final-report-task-force-CO2-utilization.
Socolow, R.H., 2016. A Dangerous Moment for Climate Change and for Science. B. Atom. Sci., November 22, 2016. http:// thebulletin.org/commentary/dangerous-moment-climate-change-and-science10202.
Socolow, R.H., 2016. Fitting on the Earth: Challenges of Carbon and Nitrogen Cycle to Preserve the Habitability of the Planet. Engineering, 2(1): 21-22. doi:10.1016/J. ENG.2016.01.012.
Zhao, L., X. Lee, and N.M. Schultz, 2017. A wedge strategy for mitigation of urban warming in future climate scenarios. Atmos. Chem. Phys. Discuss., in review. doi:10.5194/acp-2016-1046.
Zhao, L., M. Oppenheimer, Q. Li, Q. Zhu, and N.M. Schultz, 2017. Designing built-up morphology for urban climate and environmental co-benefits, in preparation.
Principal funding support for the Carbon Mitigation Initiative has been provided by BP International Limited.
Carbon Mitigation Initiative Leadership and Administration
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Robert H. Socolow, co-director
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Katharine B. Hackett, executive director, Princeton Environmental Institute
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Holly P. Welles