Policy & Integration Group

Policy & Integration Group

The objective of the Policy & Integration Group is to provide policy-relevant climate risk assessments, to bring new thinking into policy formulation, and to communicate the policy relevance of CMI research. The faculty members involved are Co-Directors Stephen Pacala & Robert Socolow, Alex Glaser, Michael Oppenheimer, and M.V. Ramana.


A new focus on short-term climate variability

A new program on short-term climate variability may have found an important reason for the current hiatus in global warming and is laying the groundwork for predictions of extreme precipitation and heat waves.

Projections of sea-level rise

Risks of climate change-induced coastal flooding can now be assessed at the local level by using longterm sea level rise models linked with short-term storm surge predictions.

Expanded carbon accounting

Along with annual carbon emissions, nations should report the “committed” emissions represented by newly constructed and existing power plants as part of global carbon accounting, a new analysis suggests.

Challenges for nuclear energy

New research is examining risk-related barriers to the widespread deployment of nuclear energy, a key technology in model scenarios for meeting carbon emissions reduction targets.

Outreach efforts

CMI has continued to find that a wide audience is eager to learn about the risks of climate change and challenges of carbon mitigation. Collaboration with the Andlinger Center for Energy and the Environment is enhancing outreach efforts.

Climate risk assessment

The research on earth system science conducted within CMI facilitates its integration efforts. The Pacala and Oppenheimer groups use state-of-the art models to provide descriptions of climate risks that are relevant to policymakers.

Focus on short-term climate variability

To help anticipate the risks of near-term climate change, in 2012 BP agreed to sponsor a new research program at Princeton entitled “Climate Variability over the Next 25 Years.” Headed by Steve Pacala and Elena Shevliakova, the program involves collaborative research among BP, CMI, GFDL and the BP-sponsored team at Imperial College. The researchers are using high-resolution climate models to predict climate variability, changes in climate variability, and impacts of climate variability over the next quarter century.

Research highlights for 2013 include:

  • An investigation of the current temperature pause/hiatus. The team believes the hiatus could be related to the Atlantic Meridional Oscillation (AMO) and is working to develop a tool by this fall to estimate when this hiatus might end.
  • Completion of an analysis of Chinese drought/heat waves. Model results have not accurately reproduced historic patterns, which has led the group to hypothesize that aerosols were deficient in the model, particularly in China. They have built an aerosol and dust package into a high resolution model to solve the problem.
  • Development of a tool for analysis of extreme precipitation data. A new extreme precipitation data set has been created and the teams are working to produce an analysis documenting patterns of extreme precipitation worldwide at 25 km resolution.

Future plans include providing global predictions for extreme precipitation, predictions for city generated weather (e.g., heat waves) globally through 2050, and production of a refined drought analysis.

Assessing the risk of sea level rise

In recent years the Oppenheimer group’s focus has been on creating projections for sea-level rise that account for all relevant physical processes and are useful for risk management.

Quantifying the risk associated with future sea level rise requires the projection and aggregation of many physical processes – including ocean thermal expansion, ice sheet and glacier mass loss, and vertical land motion. Chris Little and Michael Oppenheimer remain focused on comprehensively and consistently including these processes in sea level projections, providing a more conducive basis for a risk management approach to climate change.

This year, projections derived using the researchers’ novel approach to quantifying future Antarctic ice loss were heavily cited in the IPCC’s Fifth Assessment report. The group continues to develop this framework, with ongoing efforts designed to include: 1) changes in the Greenland ice sheet mass balance; 2) the solid earth and gravitational responses that modulate sea level changes at the local level; and 3) new constraints from process-based ice sheet models, smaller-scale observations of ice loss, paleo-sea-level observations, and expert judgment.

Along with former Oppenheimer post-doc Robert Kopp, they are generating fully probabilistic projections of sea level rise at global tide gauge locations (Figure 1). These projections - which account for processes that result in sea level changes over annual to decadal timescales - are being combined with projections of short-term sea level variability (storm surge) developed by other Princeton researchers. The merged projections will be used to generate a risk assessment of coastal flooding at four coastal tide gauge locations on the East coast of the U.S. through the year 2100.

figure 1

Evaluating carbon mitigation strategies

Robert Socolow has led efforts to assess the challenges and benefits of mitigation strategies and to frame the carbon and climate problem in policy-relevant ways to spur action on carbon emissions.

“Committed” emissions

Work by Socolow with Steve Davis (UC Irvine) on “committed” emissions has led to a paper, “Commitment accounting of CO2 emissions,” that is currently under review. One argument of the paper is that the CO2 accounting reported by national governments should routinely include future emissions that are committed each year through capital investments that will run for many years. Databases on the world’s power plants reveal that annual increases in globally committed emissions in the power sector have exceeded actual annual emissions from that sector for many years (Figure 2).

figure 2

Removal of carbon from the atmosphere

Robert Socolow, with Massimo Tavoni, edited a ten-article special issue of Climatic Change on “negative emissions” which brings together technological considerations and integrated assessment models. Entitled “Carbon Dioxide Removal from the Atmosphere: Complementary Insights from Science and Modeling” the issue (Volume 113) is now publicly available online (see http://link. springer.com/journal/10584/118/1/page/1). Socolow and Tavoni wrote the overview article at the front of the issue, “Modeling meets science and technology: an introduction to a special issue on negative emissions.” Socolow co-authored another of the articles, “Direct air capture of CO2 with chemicals: optimization of a two-loop hydroxide-carbonate system using a countercurrent airliquid contactor,” with Michael Desmond (BP) as well as Marco Mazzotti (ETH, Zurich) and Renato Baciocchi (University of Rome). This special issue culminates a five-year effort to provide context for the option of removing CO2 from the atmosphere via biology or chemistry. The overall messages are sobering:

  • CO2 removal options can lower atmospheric concentrations only slowly, at a rate of 1-2 ppm per year.
  • Biomass-based strategies create large land demands that are treated too casually today in models.
  • Chemical-based removal presents formidable challenges related to cost reductions, but has much less land impact than biomass-based strategies. However, chemical options might better be applied to reduce costs for capture from concentrated sources.

Challenges for nuclear energy

Alexander Glaser and M.V. Ramana focus on how nuclear power potentially fits into a modern low-carbon energy system, with an emphasis on accident risks and new technologies. Their research project draws on expertise from the fields of computing, engineering, and policy to evaluate a range of possible alternative energy futures.

Impacts of accidents on nuclear energy’s future

Though prospects for a worldwide large-scale expansion of nuclear power have diminished following the March 2011 nuclear accident in Fukushima, Japan, some countries continue to construct nuclear reactors and a number of countries are proceeding with plans to acquire their first nuclear power plants. The International Atomic Energy Agency counts 29 countries as considering or planning for nuclear power. Proposals for including nuclear power in a nation’s energy supply mix often rely on climate change mitigation arguments.

An important focus during the past year of the Re-engineering the Nuclear Future project led by Alexander Glaser and M. V. Ramana has been to explore better ways of characterizing nuclear power in the integrated assessment models that combine detailed models of economy, energy and climate to project the climate implications of energy policies. Such models often project a need for a five to ten-fold increase in the deployment of nuclear power globally—in part because of the assumption that nuclear energy offers lower cost electricity than renewables. However, these models do not account for the potential costs and policy impacts of catastrophic nuclear accidents. The experience following the Chernobyl and Fukushima accidents suggests that reactions to severe accidents can be varied, widespread, and significant in magnitude. Further, resulting changes in safety regulations will usually translate into higher costs for nuclear power.

Glaser and Ramana worked with Shoibal Chakravarty, who developed a dynamic programming approach to include the impact of accidents on the likely deployment of nuclear power over the next few decades. Preliminary results indicate that if the probability of a Fukushima-scale accident is on the order of one in 100,000 reactor years, the role of nuclear power would be significantly smaller by the end of the century than projected with the same model when the possibility of accidents is ignored. The empirical record of accidents so far suggests an accident probability greater than one in ten thousand years, although the industry claims calculated probabilities for the latest generation of reactors lower than once in a million years. The researchers propose to explore other factors, such as the linkage with nuclear weapons proliferation, that might significantly affect the role that nuclear power could potentially play in climate mitigation.

Regulatory challenges for small modular reactors

Ramana and Glaser also continued to examine the challenges associated with a new generation of small modular reactors (SMRs) with power outputs of 100 to 300 MWe that have been proposed as a potential solution to many of the problems confronting the expansion of nuclear power. Because of their many novel features, it is critical that national nuclear regulators follow careful and thorough licensing procedures to ensure safety. The researchers find that in many cases SMR designers have argued that their reactor designs are already so safe that regulatory authorities should permit existing licensing requirements for nuclear reactors to be eased. One focus has been to allow reactors to be deployed without a sizeable zone where emergency plans for evacuating the population are put in place. This raises the concern that the safety enhancements promised in SMR designs could be offset by a simultaneous relaxation of licensing requirements leading to an overall higher risk or impacts of severe accidents to the populations living in the vicinity of reactors. Future plans include the analysis of potential accident scenarios and their radiological impact to see if such a relaxation of the emergency planning zone rules is justified.

Outreach Efforts

A key focus of the Policy & Integration Group has been communicating information about the challenges of carbon mitigation and climate change to the widest possible audience. In 2013, Robert Socolow extended our outreach efforts on multiple fronts.

Communicating uncertainty

With Melissa Lane (Professor of Politics), Socolow is co-leading a university-wide project, “Communicating uncertainty: science, institutions, and ethics in the politics of global climate change.” The project supports resident fellows, lectures, and workshops and is leading to increased commitment to the study of climate change on the part of faculty in the social sciences and the humanities, as well as enabling interdisciplinary ventures.

Distilling technical information

Socolow has embarked on a new activity, the “distillate project,” which develops summaries of new technologies for non-specialists. The project, led by Socolow and funded primarily by the Princeton’s Andlinger Center for Energy and the Environment, draws broadly on the expertise of the Princeton faculty. The first distillate, drafted in 2013, addresses electricity storage and its potential to provide cost-effective options for the electricity grid as it seeks to increase reliability and accepts an increasing share of intermittent renewable sources. Subsequent distillates will address geothermal energy and small modular nuclear reactors.

Grand Challenges for Engineering

From 2006 through 2009, Socolow was a member of the Grand Challenges for Engineering Committee of the National Academy of Engineering (NAE). In 2013, this committee was revived to provide advice to the authors of the NAE 50th Anniversary Book, which will have five chapters, positioned in 1964, 1989, 2014, 2039, and 2064. In NAE’s words: “the goal of the project is to tell compelling stories about engineering innovations and advances that communicate the essential role of engineering in our daily lives and in the security and prosperity of the nation and society.”

Stabilization Wedges

With a guest lecture, for the second consecutive year, Socolow introduced an adaptation of the Wedges Game that is now played annually in May by an honors group of engineering undergraduate students from the Politecnico di Milano and the Politecnico di Torino. The game is the capstone of their week-long retreat, the Alta Scuola Politecnica (ASP), Belgirate, Italy.

Policy & Integration Publications

Ahmad, A., E.B. McClamrock, and A. Glaser, 2014. Denatured-fuel molten salt reactors: Resource requirements and proliferation-risk attributes. Nuclear Technology, submitted.

Arnold, C., G. Davies, T. Kreutz, W. Powell, M. Schwartz, R. Socolow, and D. Steingart, 2014. Grid–Scale Electricity Storage for Burgeoning Renewable Energy: Challenges and Opportunities. An Energy Technology Distillate from the Andlinger Center for Energy and the Environment, February 9.

Davis, S.J. and R.H. Socolow, 2014. Commitment accounting of CO2 emissions. Nature Climate Change, under review.

Kopp, R.E., D. J. Rasmussen, C.M. Little, M. Oppenheimer, J.X. Mitrovic, 2014. Probabilistic 21st century sea-level rise projections at a global network of tide gauge sites, submitted.

Horton, R. et al., 2014. A Framework for Rapid Assessment of Climate Hazards in New York City Post-Hurricane Sandy: Part 1, Atmospheric Variables, submitted.

Horton, R., et al., 2014 A Framework for Rapid Assessment of Climate Hazards in New York City Post-Hurricane Sandy: Part 2, Sea Level Rise, submitted.

Little, C., 2013. Contributing Author, Chapter 13: Sea Level Change. IPCC Fifth Assessment Report.

Mazzotti, M., R. Baciocchi,, M.J. Desmond, and R.H. Socolow, 2013. Direct air capture of CO2 with chemicals: optimization of a two-loop hydroxide-carbonate system using a countercurrent air-liquid contactor. Climatic Change, Volume 118, Issue 1: pages 119-135.

Ramana, M.V., L.B. Hopkins, and A. Glaser, 2013. Licensing small modular reactors. Energy 61: 555–64. doi:10.1016/j. energy.2013.09.010.

Ramana, M.V., 2013. Nuclear policy responses to Fukushima: Exit, Voice, and Loyalty. Bulletin of the Atomic Scientists 69 (2): 66–76.

Ramana, M. V. and Z. Mian, 2014. One size doesn’t fit all: Social priorities and technical conflicts for small modular reactors. Energy Research and Social Science, submitted.

Tavoni, M., and R. H. Socolow. Modeling meets science and technology: An introduction to a special issue on negative emissions. Climatic Change, Volume 118, Issue 1: pages 1-14. 2013.


Principal funding support for the Carbon Mitigation Initiative has been provided by BP International Limited.

Carbon Mitigation Initiative Leadership and Administration

Stephen W. Pacala, co-director
Robert H. Socolow, co-director

Rajeshri D. Chokshi, technical support specialist
Stacey T. Christian, business administration
Caitlin Daley, administrative assistant
Katharine B. Hackett, associate director, Princeton Environmental Institute
Axel Haenssen, technical support specialist
Igor Heifetz, webmaster
Roberta M. Hotinski, science communication consultant
Shavonne L. Malone, administrative assistant
Pascale M. Poussart, former assistant director, energy initiatives
Holly P. Welles, manager, communications and outreach

Contributing Editors

Roberta M. Hotinski
Holly P. Welles

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