Publications

Advanced Filters

2016

Hallegatte, Stéphane et al. “Make Climate-Change Assessments More Relevant.” Nature Vol. 534.Issue 7609 (2016): n. pag. Print.
Hallegatte, Stephane et al. “Mapping the Climate Change Challenge.” Nature Climate Change Vol. 6 (2016): pp.663–668. Print.
Discussions on a long-term global goal to limit climate change, in the form of an upper limit to warming, were only partially resolved at the United Nations Framework Convention on Climate Change negotiations in Paris, 2015. Such a political agreement must be informed by scientific knowledge. One way to communicate the costs and benefits of policies is through a mapping that systematically explores the consequences of different choices. Such a multi-disciplinary effort based on the analysis of a set of scenarios helped structure the IPCC AR5 Synthesis Report. This Perspective summarizes this approach, reviews its strengths and limitations, and discusses how decision-makers can use its results in practice. It also identifies research needs that can facilitate integrated analysis of climate change and help better inform policy-makers and the public.
Mastrorillo, Marina et al. “The Influence of Climate Variability on Internal Migration Flows in South Africa.” Global Environmental Change Vol. 39 (2016): pp. 155–169. Print.
This work investigates the impact of climate variability on internal migration flows in post-apartheid South Africa. We combine information from South African censuses and climatic data to build a panel database covering the waves 1997–2001 and 2007–2011. The database enables the examination of the effect of spatiotemporal variability in temperature and precipitation on inter-district migration flows defined by five-year intervals. We employ a gravity approach where bilateral migration flows are explained by climate variability at the origin, along with a number of geographic, socio-economic and demographic factors traditionally identified as potential drivers of migration. Overall, we find that an increase in positive temperature extremes as well as positive and negative excess rainfall at the origin act as a push effect and enhance out-migration. However, the significance of the effect of climate on migration greatly varies by migrant characteristics. Particularly, flows of black and low-income South African migrants are strongly influenced by climatic variables whereas those of white and high-income migrants exhibit a weak impact. We also argue that agriculture may function as a transmission channel through which adverse climatic conditions affect migration.
Buchanan, Maya K. et al. “Allowances for Evolving Coastal Flood Risk under Uncertain Local Sea-Level Rise.” Climatic Change Vol.137 (2016): pp.347–362. Print.
Estimates of future flood hazards made under the assumption of stationary mean sea level are biased low due to sea-level rise (SLR). However, adjustments to flood return levels made assuming fixed increases of sea level are also inadequate when applied to sea level that is rising over time at an uncertain rate. SLR allowances—the height adjustment from historic flood levels that maintain under uncertainty the annual expected probability of flooding—are typically estimated independently of individual decision-makers’ preferences, such as time horizon, risk tolerance, and confidence in SLR projections. We provide a framework of SLR allowances that employs complete probability distributions of local SLR and a range of user-defined flood risk management preferences. Given non-stationary and uncertain sea-level rise, these metrics provide estimates of flood protection heights and offsets for different planning horizons in coastal areas. We illustrate the calculation of various allowance types for a set of long-duration tide gauges along U.S. coastlines.
Keohane, Robert, and Michael Oppenheimer. “Paris: Beyond the Climate Dead End Through Pledge and Review?.” Politics and Governance Vol. 4 (2016): n. pag. Print.
 The Paris Climate Agreement of December 2015 marks a decisive break from the unsuccessful Kyoto regime. Instead of targets and timetables, it established a Pledge and Review system, under which states will offer Nationally Determined Contributions (INDCs) to reducing emissions that cause climate change. But this successful negotiation outcome was achieved at the price of vagueness of obligations and substantial discretion for governments. Many governments will be tempted to use the vagueness of the Paris Agreement, and the discretion that it permits, to limit the scope or intensity of their proposed actions. Whether Pledge and Review under the Paris Agreement will lead to effective action against climate change will therefore depend on the inclination both of OECD countries and newly industrializing countries to take costly actions, which for the OECD countries will include financial transfers to their poorer partners. Domestic politics will be crucial in determining the attitudes of both sets of countries to pay such costs. The actual impact of the Paris Agreement will depend on whether it can be used by domestic groups favoring climate action as a point of leverage in domestic politics—that is, in a “two-level game” simultaneously involving both international and domestic politics.
Alley, Richard, and Michael Oppenheimer. “How High Will the Seas Rise?.” Science Vol. 354.Issue 6318 (2016): pp. 1375–1377. Print.
Recent estimates suggest that global mean sea level rise could exceed 2 m by 2100. These projections are higher than previous ones and are based on the latest understanding of how the Antarctic Ice Sheet has behaved in the past and how sensitive it is to future climate change. They pose a challenge for scientists and policy-makers alike, requiring far-reaching decisions about coastal policies to be made based on rapidly evolving projections with large, persistent uncertainties. An effective approach to managing coastal risk should couple research priorities to policy needs, enabling judicious decision-making while focusing research on key questions.
Bohra-Mishra, Pratikshya et al. “Climate Variability and Migration in the Philippines.” Popul Environ vol 38 (2016): pp. 286–308. Print.
This study investigates the effects of climatic variations and extremes captured by variability in temperature, precipitation, and incidents of typhoons on aggregate inter-provincial migration within the Philippines using panel data. Our results indicate that a rise in temperature and to some extent increased typhoonactivity increase outmigration, while precipitation does not have a consistent, significant effect. We also find that temperature and typhoons have significant negative effects on rice yields, a proxy for agricultural productivity, and generate more outmigration from provinces that are more agriculturally dependent and have a larger share of rural population. Finally, migration decisions of males, younger individuals, and those with higher levels of education are more sensitive to rising temperature and typhoons. We conclude that temperature increase and to some extent typhoon activities promote migration, potentially through their negative effect on crop yields. The migration responses of males, more educated, and younger individuals are more sensitive to these climatic impacts

2015

Little, Christopher et al. “Uncertainty in Twenty-First-Century CMIP5 Sea Level Projections.” Journal of Climate vol. 28 (2015): pp. 838–852. Print.
 

The representative concentration pathway (RCP) simulations included in phase 5 of the Coupled Model Intercomparison Project (CMIP5) quantify the response of the climate system to different natural and anthropogenic forcing scenarios. These simulations differ because of 1) forcing, 2) the representation of the climate system in atmosphere–ocean general circulation models (AOGCMs), and 3) the presence of unforced (internal) variability. Global and local sea level rise projections derived from these simulations, and the emergence of distinct responses to the four RCPs depend on the relative magnitude of these sources of uncertainty at different lead times. Here, the uncertainty in CMIP5 projections of sea level is partitioned at global and local scales, using a 164-member ensemble of twenty-first-century simulations. Local projections at New York City (NYSL) are highlighted. The partition between model uncertainty, scenario uncertainty, and internal variability in global mean sea level (GMSL) is qualitatively consistent with that of surface air temperature, with model uncertainty dominant for most of the twenty-first century. Locally, model uncertainty is dominant through 2100, with maxima in the North Atlantic and the Arctic Ocean. The model spread is driven largely by 4 of the 16 AOGCMs in the ensemble; these models exhibit outlying behavior in all RCPs and in both GMSL and NYSL. The magnitude of internal variability varies widely by location and across models, leading to differences of several decades in the local emergence of RCPs. The AOGCM spread, and its sensitivity to model exclusion and/or weighting, has important implications for sea level assessments, especially if a local risk management approach is utilized.

 

Little, Christopher et al. “Joint Projections of US East Coast Sea Level and Storm Surge.” Nature Climate Change vol 5 (2015): n. pag. Print.
 

Future coastal flood risk will be strongly influenced by sea-level rise (SLR) and changes in the frequency and intensity of tropical cyclones. These two factors are generally considered independently. Here, we assess twenty-first century changes in the coastal hazard for the US East Coast using a flood index (FI) that accounts for changes in flood duration and magnitude driven by SLR and changes in power dissipation index (PDI, an integrated measure of tropical cyclone intensity, frequency and duration). Sea-level rise and PDI are derived from representative concentration pathway (RCP) simulations of 15 atmosphere–ocean general circulation models (AOGCMs). By 2080–2099, projected changes in the FI relative to 1986–2005 are substantial and positively skewed: a 10th–90th percentile range 4–75 times higher for RCP 2.6 and 35–350 times higher for RCP 8.5. High-end FI projections are driven by three AOGCMs that project the largest increases in SLR, PDI and upper ocean temperatures. Changes in PDI are particularly influential if their intra-model correlation with SLR is included, increasing the RCP 8.5 90th percentile FI by a further 25%. Sea-level rise from other, possibly correlated, climate processes (for example, ice sheet and glacier mass changes) will further increase coastal flood risk and should be accounted for in comprehensive assessme

Horton, Radley et al. “New York City Panel on Climate Change 2015 Report Chapter 2: Sea Level Rise and Coastal Storms.” Annals of the New York Academy of Sciences (2015): n. pag. Print.
Oppenheimer, Michael. “Adapting to Climate Change: Rising Sea Levels, Limiting Risks.” Social Research: An International Quarterly vol.82 (2015): pp. 673–680. Print.
Climate change and resulting sea level rise will cause risk from coastal storms to increase throughout this century. Aggressive implementation of emissions reduction policies would significantly limit the risk but in any event, planning for comprehensive adaptation is necessary. Past experience with long term planning to reduce vulnerability and exposure along the coast shows a significant shortfall between the need to reduce risk and the implementation of appropriate policies. A new approach to public policy in this arena should be a priority for policy makers.
Wagner, Gernot et al. “Energy Policy: Push Renewables to Spur Carbon Pricing.” Nature vol 525.issue 7567 (2015): n. pag. Print.
Hannam, Phillip M. et al. “Developing Country Finance in a Post-2020 Global Climate Agreement.” Nature Climate Change Vol. 5 (2015): pp. 983–987. Print.
A central task for negotiators of the post-2020 global climate agreement is to construct a finance regime that supports low-carbon development in developing economies. As power sector investments between developing countries grow, the climate finance regime should incentivize the decarbonization of these major sources of finance by integrating them as a complement to the commitments of developed nations. The emergence of the Asian Infrastructure Investment Bank, South–South Cooperation Fund and other nascent institutions reveal the fissures that exist in rules and norms surrounding international finance in the power sector. Structuring the climate agreement in Paris to credit qualified finance from the developing world could have several advantages, including: (1) encouraging low-carbon cooperation between developing countries; (2) incentivizing emerging investors to prefer low-carbon investments; and (3) enabling more cost-effective attainment of national and global climate objectives. Failure to coordinate on standards now could hinder low-carbon development in the decades to come.

2014

Lloyd, Ian, and Michael Oppenheimer. “On the Design of an International Governance Framework for Geoengineering.” Global Environmental Politics vol. 14 (2014): pp.45–63. Print.
This paper explores the governance options surrounding geoengineering—the deliberate, large-scale manipulation of the Earth’s climate system to counteract climate change. The authors focus solely on methods that affect the incoming solar radiation to the atmosphere, referred to as solar radiation management (SRM). They examine whether an international governance framework for SRM is needed, how it should be designed, and whether it is feasible. The authors propose a governance regime that initially has small membership and weak legalization, and is flexible in that future institutional reforms allow for broader membership and deeper commitments. The article provides supporting evidence for key aspects of the regime through past international treaties in arms control and environmental protection, including the Antarctica, Outer Space, and Montreal Protocol treaty regimes. For these cases, acting early and treating the respective problems as part of the “regulation of unexplored territory” produced more effective outcomes than the “national appropriation” approach that characterizes arms control.
Cai, Ruohong, Danlin Yu, and Michael Oppenheimer. “Estimating the Spatially Varying Responses of Corn Yields to Weather Variations Using Geographically Weighted Panel Regression.” Journal of Agricultural and Resource Economics vol 39 (2014): pp. 230–252. Print.
Researchers have extensively studied crop yield response to weather variations, while only a limited number of studies have attempted to identify spatial heterogeneity in this relationship. We explore spatial heterogeneity in corn yield response to weather by combining geographically weighted regression and panel regression. We find that temperature tends to have negative effects on U.S. corn yields in warmer regions and positive effects in cooler regions, with spatial heterogeneity at a fine scale. The spatial pattern of precipitation effects is more complicated. A further analysis shows that precipitation effects are sensitive to the existence of irrigation systems.
Bohra-Mishra, Pratikshya, Michael Oppenheimer, and Solomon Hsiang. “Nonlinear Permanent Migration Response to Climatic Variations But Minimal Response to Disasters.” PNAS vol 111 (2014): pp.9780–9785. Print.
 

We present a microlevel study to simultaneously investigate the effects of variations in temperature and precipitation along with sudden natural disasters to infer their relative influence on migration that is likely permanent. The study is made possible by the availability of household panel data from Indonesia with an exceptional tracking rate combined with frequent occurrence of natural disasters and significant climatic variations, thus providing a quasi-experiment to examine the influence of environment on migration. Using data on 7,185 households followed over 15 y, we analyze whole-household, province-to-province migration, which allows us to understand the effects of environmental factors on permanent moves that may differ from temporary migration. The results suggest that permanent migration is influenced by climatic variations, whereas episodic disasters tend to have much smaller or no impact on such migration. In particular, temperature has a nonlinear effect on migration such that above 25 °C, a rise in temperature is related to an increase in outmigration, potentially through its impact on economic conditions. We use these results to estimate the impact of projected temperature increases on future permanent migration. Though precipitation also has a similar nonlinear effect on migration, the effect is smaller than that of temperature, underscoring the importance of using an expanded set of climatic factors as predictors of migration. These findings on the minimal influence of natural disasters and precipitation on permanent moves supplement previous findings on the significant role of these variables in promoting temporary migration.

Keohane, Robert O., Melissa Lane, and Michael Oppenheimer. “The Ethics of Scientific Communication under Uncertainty.” Politics, Philosophy & Economics vol. 13.issue 4 (2014): pp. 343– 368. Print.
 

Communication by scientists with policy makers and attentive publics raises ethical issues. Scientists need to decide how to communicate knowledge effectively in a way that nonscientists can understand and use, while remaining honest scientists and presenting estimates of the uncertainty of their inferences. They need to understand their own ethical choices in using scientific information to communicate to audiences. These issues were salient in the Fourth Assessment of the Intergovernmental Panel on Climate Change with respect to possible sea level rise from disintegration of the Greenland and West Antarctic ice sheets. Due to uncertainty, the reported values of projected sea level rise were incomplete, potentially leading some relevant audiences to underestimate future risk. Such judgments should be made in a principled rather than an ad hoc manner. Five principles for scientific communication under such conditions are important: honesty, precision, audience relevance, process transparency, and specification of uncertainty about conclusions. Some of these principles are of intrinsic importance while others are merely instrumental and subject to trade-offs among them. Scientists engaged in assessments under uncertainty should understand these principles and which trade-offs are acceptable.

Kopp, Robert E. et al. “Probabilistic 21st and 22nd Century sea‐level Projections at a Global Network of tide‐gauge Sites.” Earth’s Future vol.2.issue 8 (2014): n. pag. Print.

Sea‐level rise due to both climate change and non‐climatic factors threatens coastal settlements, infrastructure, and ecosystems. Projections of mean global sea‐level (GSL) rise provide insufficient information to plan adaptive responses; local decisions require local projections that accommodate different risk tolerances and time frames and that can be linked to storm surge projections. Here we present a global set of local sea‐level (LSL) projections to inform decisions on timescales ranging from the coming decades through the 22nd century. We provide complete probability distributions, informed by a combination of expert community assessment, expert elicitation, and process modeling. Between the years 2000 and 2100, we project a very likely (90% probability) GSL rise of 0.5–1.2 m under representative concentration pathway (RCP) 8.5, 0.4–0.9 m under RCP 4.5, and 0.3–0.8 m under RCP 2.6. Site‐to‐site differences in LSL projections are due to varying non‐climatic background uplift or subsidence, oceanographic effects, and spatially variable responses of the geoid and the lithosphere to shrinking land ice. The Antarctic ice sheet (AIS) constitutes a growing share of variance in GSL and LSL projections. In the global average and at many locations, it is the dominant source of variance in late 21st century projections, though at some sites oceanographic processes contribute the largest share throughout the century. LSL rise dramatically reshapes flood risk, greatly increasing the expected number of “1‐in‐10” and “1‐in‐100” year events.

Cai, Ruohong et al. “International Migration Desires Related to Subjective Well-Being.” IZA Journal of Development and Migration vol. 3 (2014): n. pag. Print.
Previous research on the determinants of international migration has largely focused on objective factors, such as income. We instead use subjective well-being (SWB) to explain international migration desires, an expressed willingness to migrate. We find that individuals with higher SWB have lower international migration desires. At the individual level, the SWB-migration relationship appears to be more robust than the income-migration relationship. At the country level, national average SWB better indicates international migration desires for rich countries, while income performs better for poor countries. We thus demonstrate the feasibility of employing subjective measures to study at least one aspect of an important social outcome, migration.
Oppenheimer, Michael. “Warming Goal: Still the Best Indicator.” Nature vol 514 (2014): pp.434. Print.
Li, Dan, Elie Bou-Zeid, and Michael Oppenheimer. “The Effectiveness of Cool and Green Roofs As Urban Heat Island Mitigation Strategies.” Environmental Research Letters Vol 9 (2014): n. pag. Print.
Mitigation of the urban heat island (UHI) effect at the city-scale is investigated using the Weather Research and Forecasting (WRF) model in conjunction with the Princeton Urban Canopy Model (PUCM). Specifically, the cooling impacts of green roof and cool (white/high-albedo) roof strategies over the Baltimore-Washington metropolitan area during a heat wave period (7 June–10 June 2008) are assessed using the optimal set-up of WRF-PUCM described in the companion paper by Li and Bou-Zeid (2014). Results indicate that the surface UHI effect (defined based on the urban–rural surface temperature difference) is reduced significantly more than the near-surface UHI effect (defined based on urban–rural 2 m air temperature difference) when these mitigation strategies are adopted. In addition, as the green and cool roof fractions increase, the surface and near-surface UHIs are reduced almost linearly. Green roofs with relatively abundant soil moisture have comparable effect in reducing the surface and near-surface UHIs to cool roofs with an albedo value of 0.7. Significant indirect effects are also observed for both green and cool roof strategies; mainly, the low-level advection of atmospheric moisture from rural areas into urban terrain is enhanced when the fraction of these roofs increases, thus increasing the humidity in urban areas. The additional benefits or penalties associated with modifications of the main physical determinants of green or cool roof performance are also investigated. For green roofs, when the soil moisture is increased by irrigation, additional cooling effect is obtained, especially when the 'unmanaged' soil moisture is low. The effects of changing the albedo of cool roofs are also substantial. These results also underline the capabilities of the WRF-PUCM framework to support detailed analysis and diagnosis of the UHI phenomenon, and of its different mitigation strategies.
Richard L. Revesz et al. “ Improve Economic Models of Climate Change.” Nature Vol 508.Issue 7495 (2014): pp.173–175. Print.

2013

Estes, Lyndon D. et al. “Projected Climate Impacts to South African Maize and Wheat Production in 2055: A Comparison of Empirical and Mechanistic Modeling Approaches.” Global Change Biology vol. 19 .issue 12 (2013): n. pag. Print.
Crop model‐specific biases are a key uncertainty affecting our understanding of climate change impacts to agriculture. There is increasing research focus on intermodel variation, but comparisons between mechanistic (MM s) and empirical models (EM s) are rare despite both being used widely in this field. We combined MM s and EM s to project future (2055) changes in the potential distribution (suitability) and productivity of maize and spring wheat in S outh A frica under 18 downscaled climate scenarios (9 models run under 2 emissions scenarios). EM s projected larger yield losses or smaller gains than MM s. The EM s’ median‐projected maize and wheat yield changes were −3.6% and 6.2%, respectively, compared to 6.5% and 15.2% for the MM . The EM projected a 10% reduction in the potential maize growing area, where the MM projected a 9% gain. Both models showed increases in the potential spring wheat production region (EM  = 48%, MM  = 20%), but these results were more equivocal because both models (particularly the EM ) substantially overestimated the extent of current suitability. The substantial water‐use efficiency gains simulated by the MM s under elevated CO 2 accounted for much of the EM −MM difference, but EM s may have more accurately represented crop temperature sensitivities. Our results align with earlier studies showing that EM s may show larger climate change losses than MM s. Crop forecasting efforts should expand to include EM −MM comparisons to provide a fuller picture of crop–climate response uncertainties.
Oppenheimer, Michael, Bryce Rudyk, and R.B. Stewart. “Building a More Effective Global Climate Regime Through a Bottom-Up Approach.” Theoretical Inquiries in Law vol. 14 .issue 1 (2013): pp.273–306. Print.
This Article presents an innovative institutional strategy for global climate protection, quite distinct from, but ultimately complementary to and supportive of the currently stalled UNFCCC climate treaty negotiations. The bottom-up strategy relies on a variety of smallerscale transnational cooperative arrangements, involving not only states but sub-national jurisdictions, firms, and CSOs, to undertake activities whose primary goal is not climate mitigation but which will achieve greenhouse gas reductions as an inherent byproduct. This strategy avoids the inherent problems in securing an enforceable treaty to secure the global public good of climate protection by mobilizing other incentives - including economic self-interest, energy security, cleaner air, and furtherance of international development - to motivate such actors to cooperate on actions that will also benefit the climate. These bottom-up regimes will contribute to global climate action not only by achieving emissions reductions in the short-term, but also by linking the bottom-up regimes to the UNFCCC system through greenhouse gas monitoring and reporting systems. In these ways, the bottom-up strategy will help secure eventual agreement on a global climate treaty.
Escarra, M.D. et al. “Quantum Cascade Laser-Based Sensing for Carbon Sequestration Leakage Monitoring.” IEEE Sensors Journal vol. 13.no.6 (2013): pp. 2348–2356. Print.
Carbon capture and sequestration (CCS) may play a key role in our energy future. However, the widespread sequestration of CO2 into storage reservoirs is inhibited by safety and leakage concerns. Effective leakage monitoring at the surface is recently made possible by the development of quantum cascade (QC) laser-based sensors, which are capable of tracking fluxes in CO2 isotope concentrations. In this paper, we initially discuss the status of this technology, including recent results from distributed feedback QC lasers for use in sensing CO2 isotopic ratios. These lasers show single-mode emission at 4.32 μm, overlapping strong absorption resonances of 12CO2, 13CO2, and 18OCO. We then consider the value of such devices for quantifying CO2 leakage using a climate-economy integrated-assessment model that is modified to include CCS. The sensitivity of model outcomes to reservoir leakage is studied, showing that an average reservoir storage half-life on the order of 1000 years or longer can limit atmospheric temperature increases to 2°C or less over the next 150 years for economically optimal emissions scenarios. The present day economic value of CCS is established versus reservoir half-life, showing a significant return on investment ( ~ 2 trillion U.S.$, or ~ 4% of gross world product) when the average reservoir half-life is 250 years, with a sharp drop in the value of CCS technology for half-life values below 250 years. Quantifying CO2 leakage rates via QC laser-based sensing will contribute greatly toward accurately assessing CCS technology and its efficacy as part of CO2 limitation strategies.
Estes, Lyndon D. et al. “Using Changes in Agricultural Utility to Quantify Future Climate‐Induced Risk to Conservation.” Conservation Biology vol. 28.issue 2 (2013): n. pag. Print.
Much of the biodiversity‐related climate change impacts research has focused on the direct effects to species and ecosystems. Far less attention has been paid to the potential ecological consequences of human efforts to address the effects of climate change, which may equal or exceed the direct effects of climate change on biodiversity. One of the most significant human responses is likely to be mediated through changes in the agricultural utility of land. As farmers adapt their practices to changing climates, they may increase pressure on some areas that are important to conserve (conservation lands) whereas lessening it on others. We quantified how the agricultural utility of South African conservation lands may be altered by climate change. We assumed that the probability of an area being farmed is linked to the economic benefits of doing so, using land productivity values to represent production benefit and topographic ruggedness as a proxy for costs associated with mechanical workability. We computed current and future values of maize and wheat production in key conservation lands using the DSSAT4.5 model and 36 crop‐climate response scenarios. Most conservation lands had, and were predicted to continue to have, low agricultural utility because of their location in rugged terrain. However, several areas were predicted to maintain or gain high agricultural utility and may therefore be at risk of near‐term or future conversion to cropland. Conversely, some areas were predicted to decrease in agricultural utility and may therefore prove easier to protect from conversion. Our study provides an approximate but readily transferable method for incorporating potential human responses to climate change into conservation planning.
Stewart, Richard B., Michael Oppenheimer, and Bryce Rudyk. “A New Strategy for Global Climate Protection.” Climatic Change vol.120 (2013): pp.1–12. Print.
 

This essay proposes an innovative institutional strategy for global climate protection, quite distinct from but ultimately complementary to the UNFCCC climate treaty negotiations. Our “building block” strategy relies on a variety of smaller-scale transnational cooperative arrangements, involving not only states, but also subnational jurisdictions, firms, and civil society organizations, to undertake activities whose primary goal is not climate mitigation but which will achieve greenhouse gas reductions as a byproduct. This strategy avoids the problems inherent in developing an enforceable, comprehensive treaty regime by mobilizing other incentives—including economic self-interest, energy security, cleaner air, and furtherance of international development— to motivate a range of actors to cooperate on actions that will also produce climate benefits. The strategy uses three specific models of regime formation (club, linkage, and dominant actor models) which emerge from economics, international relations, and organizational behavior, to develop a variety of transnational regimes that are generally self-enforcing and sustainable, avoiding the free rider and compliance problems endemic in collective action to provide public goods. These regimes will contribute to global climate action not only by achieving emissions reductions in the short term, but also by creating global webs of cooperation and trust, and by linking the building block regimes to the UNFCCC system through greenhouse gas monitoring and reporting systems. We argue that the building blocks regimes would thereby help secure eventual agreement on a comprehensive climate treaty.

Little, Christopher M., Michael Oppenheimer, and Nathan M. Urban. “Upper Bounds on Twenty-First-Century Antarctic Ice Loss Assessed Using a Probabilistic Framework.” Nature Climate Change Vol. 3 (2013): pp.654–659. Print.
Climate adaptation and flood risk assessments1,2 have incorporated sea-level rise (SLR) projections developed using semi-empirical methods3,4,5 (SEMs) and expert-informed mass-balance scenarios2,6. 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 estimates7. However, the physical basis underlying these projections, and their likelihood of occurrence, remain unclear8,9,10. Here, we develop mass-balance projections for the Antarctic ice sheet within a Bayesian probabilistic framework10, integrating numerical model output11 and updating projections with an observational synthesis12. 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.
Little, Chris M., Nathan M. Urban, and Michael Oppenheimer. “Probabilistic Framework for Assessing the Ice Sheet Contribution to Sea Level Change.” PNAS Vol. 110 (2013): pp. 3264–3269. Print.
Previous sea level rise (SLR) assessments have excluded the potential for dynamic ice loss over much of Greenland and Antarctica, and recently proposed “upper bounds” on Antarctica’s 21st-century SLR contribution are derived principally from regions where present-day mass loss is concentrated (basin 15, or B15, drained largely by Pine Island, Thwaites, and Smith glaciers). Here, we present a probabilistic framework for assessing the ice sheet contribution to sea level change that explicitly accounts for mass balance uncertainty over an entire ice sheet. Applying this framework to Antarctica, we find that ongoing mass imbalances in non-B15 basins give an SLR contribution by 2100 that: (i) is comparable to projected changes in B15 discharge and Antarctica’s surface mass balance, and (ii) varies widely depending on the subset of basins and observational dataset used in projections. Increases in discharge uncertainty, or decreases in the exceedance probability used to define an upper bound, increase the fractional contribution of non-B15 basins; even weak spatial correlations in future discharge growth rates markedly enhance this sensitivity. Although these projections rely on poorly constrained statistical parameters, they may be updated with observations and/or models at many spatial scales, facilitating a more comprehensive account of uncertainty that, if implemented, will improve future assessments.
Estes, Lyndon D. et al. “Comparing Mechanistic and Empirical Model Projections of Crop Suitability and Productivity: Implications for Ecological Forecasting.” Global Ecology and Biogeography Vol. 22.Issue 8 (2013): n. pag. Print.
Intercomparison of mechanistic and empirical models is an important step towards improving projections of potential species distribution and abundance. We aim to compare suitability and productivity estimates for a well‐understood crop species to evaluate the strengths and weaknesses of mechanistic versus empirical modelling.
Kopp, Robert et al. “A Probabilistic Assessment of Sea Level Variations Within the Last Interglacial Stage.” Geophysical Journal International Vol.193.Issue 2 (2013): pp.711–716. Print.
The last interglacial stage (LIG; ca. 130–115 ka) provides a relatively recent example of a world with both poles characterized by greater-than-Holocene temperatures similar to those expected later in this century under a range of greenhouse gas emission scenarios. Previous analyses inferred that LIG mean global sea level (GSL) peaked 6–9 m higher than today. Here, we extend our earlier work to perform a probabilistic assessment of sea level variability within the LIG highstand. Using the terminology for probability employed in the Intergovernmental Panel on Climate Change assessment reports, we find it extremely likely (95 per cent probability) that the palaeo-sea level record allows resolution of at least two intra-LIG sea level peaks and likely (67 per cent probability) that the magnitude of low-to-high swings exceeded 4 m. Moreover, it is likely that there was a period during the LIG in which GSL rose at a 1000-yr average rate exceeding 3 m kyr−1, but unlikely (33 per cent probability) that the rate exceeded 7 m kyr−1 and extremely unlikely (5 per cent probability) that it exceeded 11 m kyr−1. These rate estimates can provide insight into rates of Greenland and/or Antarctic melt under climate conditions partially analogous to those expected in the 21st century.

2012

Feng, Shuaizhang, Alan Krueger, and M. Oppenheimer. “Applying Statistical Models to the climate–migration Relationship (letter of Correction To: 2010 Linkages Among Climate Change Crop Yields and Mexico-US Cross-Border Migrations.” PNAS vol109 (2012): pp. e2915. Print.
D.N.Goldberg et al. “Investigation of Land ice‐ocean Interaction With a Fully Coupled ice‐ocean Model: 2. Sensitivity to External Forcings.” Journal of Geophysical Research: Earth Surface vol 117.Issue F2 (2012): n. pag. Print.
[1] A coupled ice stream‐ice shelf‐ocean cavity model is used to assess the sensitivity of the coupled system to far‐field ocean temperatures, varying from 0.0 to 1.8°C, as well as sensitivity to the parameters controlling grounded ice flow. A response to warming is seen in grounding line retreat and grounded ice loss that cannot be inferred from the response of integrated melt rates alone. This is due to concentrated thinning at the ice shelf lateral margin, and to processes that contribute to this thinning. Parameters controlling the flow of grounded ice have a strong influence on the response to sub‐ice shelf melting, but this influence is not seen until several years after an initial perturbation in temperatures. The simulated melt rates are on the order of that observed for Pine Island Glacier in the 1990s. However, retreat rates are much slower, possibly due to unrepresented bedrock features.
D.N.Goldberg et al. “Investigation of Land ice‐ocean Interaction With a Fully Coupled ice‐ocean Model: 1. Model Description and Behavior.” Journal of Geophysical Research: Earth Surface vol. 117.issue F2 (2012): n. pag. Print.
[1] Antarctic ice shelves interact closely with the ocean cavities beneath them, with ice shelf geometry influencing ocean cavity circulation, and heat from the ocean driving changes in the ice shelves, as well as the grounded ice streams that feed them. We present a new coupled model of an ice stream‐ice shelf‐ocean system that is used to study this interaction. The model is capable of representing a moving grounding line and dynamically responding ocean circulation within the ice shelf cavity. Idealized experiments designed to investigate the response of the coupled system to instantaneous increases in ocean temperature show ice‐ocean system responses on multiple timescales. Melt rates and ice shelf basal slopes near the grounding line adjust in 1–2 years, and downstream advection of the resulting ice shelf thinning takes place on decadal timescales. Retreat of the grounding line and adjustment of grounded ice takes place on a much longer timescale, and the system takes several centuries to reach a new steady state. During this slow retreat, and in the absence of either an upward‐or downward‐sloping bed or long‐term trends in ocean heat content, the ice shelf and melt rates maintain a characteristic pattern relative to the grounding line.
Little, Christopher M. “On the Coupled Response to Ice-Sheet Melting.” Journal of Glaciology vol.58.issue 208 (2012): pp.203–215. Print.
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 area- average 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)
Brysse, Keynyn et al. “Climate Change Prediction: Erring on the Side of Least Drama?.” Global Environmental Change vol. 23.issue 1 (2012): pp. 327–337. Print.
Over the past two decades, skeptics of the reality and significance of anthropogenic climate change have frequently accused climate scientists of ‘‘alarmism’’: of over-interpreting or overreacting to evidence of human impacts on the climate system. However, the available evidence suggests that scientists have in fact been conservative in their projections of the impacts of climate change. In particular, we discuss recent studies showing that at least some of the key attributes of global warming from increased atmospheric greenhouse gases have been under-predicted, particularly in IPCC assessments of the physical science, by Working Group I. We also note the less frequent manifestation of over-prediction of key characteristics of climate in such assessments. We suggest, therefore, that scientists are biased not toward alarmism but rather the reverse: toward cautious estimates, where we define caution as erring on the side of less rather than more alarming predictions. We call this tendency ‘‘erring on the side of least drama (ESLD).’’ We explore some cases of ESLD at work, including predictions of Arctic ozone depletion and the possible disintegration of the West Antarctic ice sheet, and suggest some possible causes of this directional bias, including adherence to the scientific norms of restraint, objectivity, skepticism, rationality, dispassion, and moderation. We conclude with suggestions for further work to identify and explore ESLD.
Bradley, Bethany et al. “Predicting How Adaptation to Climate Change Could Affect Ecological Conservation: Secondary Impacts of Shifting Agricultural Suitability.” Biodiversity Research vol.18 (2012): pp.425–437. Print.

Aim: Ecosystems face numerous well-documented threats from climate change. The well-being of people also is threatened by climate change, most prominently by reduced food security. Human adaptation to food scarcity, including shifting agricultural zones, will create new threats for natural ecosystems. We investigated how shifts in crop suitability because of climate change may overlap currently protected areas (PAs) and priority sites for PA expansion in South Africa. Predicting the locations of suitable climate conditions for crop growth will assist conservationists and decision-makers in planning for climate change.
Location: South Africa.
Methods: We modelled climatic suitability in 2055 for maize and wheat cultivation, two extensively planted, staple crops, and overlaid projected changes with PAs and PA expansion priorities.
Results: Changes in winter climate could make an additional 2 million ha of land suitable for wheat cultivation, while changes in summer climate could expand maize suitability by up to 3.5 million ha. Conversely, 3 million ha of lands currently suitable for wheat production are predicted to become climatically unsuitable, along with 13 million ha for maize. At least 328 of 834 (39%) PAs are projected to be affected by altered wheat or maize suitability in their buffer zones.
Main conclusions: Reduced crop suitability and food scarcity in subsistence areas may lead to the exploitation of PAs for food and fuel. However, if reduced crop suitability leads to agricultural abandonment, this may afford opportunities for ecological restoration. Expanded crop suitability in PA buffer zones could lead to additional isolation of PAs if portions of newly suitable land are converted to agriculture. These results suggest that altered crop suitability will be widespread throughout South Africa, including within and around lands identified as conservation priorities. Assessing how climate change will affect crop suitability near PAs is a first step towards proactively identifying potential conflicts between human adaptation and conservation planning.

 

Feng, Shuaizhang, Michael Oppenheimer, and Wolfram Schlenker. “Climate Change, Crop Yields, and Internal Migration in the United States.” NBER Working Paper (2012): n. pag. Print.

We investigate the link between agricultural productivity and net migration in the United States using a county-level panel for the most recent period of 1970-2009. In rural counties of the Corn Belt, we find a statistically significant relationship between changes in net outmigration and climate-driven changes in crop yields, with an estimated semi-elasticity of about -0.17, i.e., a 1% decrease in yields leads to a 0.17% net reduction of the population through migration.  This effect is primarily driven by young adults. We do not detect a response for senior citizens, nor for the general population in eastern counties outside the Corn Belt. Applying this semi-elasticity to predicted yield changes under the B2 scenario of the Hadley III model, we project that, holding other factors constant, climate change would on average induce 3.7% of the adult population (ages 15-59) to leave rural counties of the Corn Belt in the medium term (2020-2049) compared to the 1960-1989 baseline, with the possibility of a much larger migration response in the long term (2077-2099). Since there is uncertainty about future warming, we also present projections for a range of uniform climate change scenarios in temperature or precipitation.

 

 

 

Lin, Ning et al. “Physically Based Assessment of Hurricane Surge Threat under Climate Change.” Nature Climate Change vol.2 (2012): pp.462–467. Print.
Storm surges are responsible for much of the damage and loss of life associated with landfalling hurricanes. Understanding how global warming will affect hurricane surges thus holds great interest. As general circulation models (GCMs) cannot simulate hurricane surges directly, we couple a GCM-driven hurricane model with hydrodynamic models to simulate large numbers of synthetic surge events under projected climates and assess surge threat, as an example, for New York City (NYC). Struck by many intense hurricanes in recorded history and prehistory, NYC is highly vulnerable to storm surges. We show that the change of storm climatology will probably increase the surge risk for NYC; results based on two GCMs show the distribution of surge levels shifting to higher values by a magnitude comparable to the projected sea-level rise (SLR). The combined effects of storm climatology change and a 1 m SLR may cause the present NYC 100-yr surge flooding to occur every 3–20 yr and the present 500-yr flooding to occur every 25–240 yr by the end of the century.
O’Reilly, Jessica, Naomi Oreskes, and Michael Oppenheimer. “The Rapid Disintegration of Projections: The West Antarctic Ice Sheet and the Intergovernmental Panel on Climate Change.” Social Studies Of Science Vol.42.Issue 5 (2012): pp.709–731. Print.
How and why did the scientific consensus about sea level rise due to the disintegration of the West Antarctic Ice Sheet (WAIS), expressed in the third Intergovernmental Panel on Climate Change (IPCC) assessment, disintegrate on the road to the fourth? Using ethnographic interviews and analysis of IPCC documents, we trace the abrupt disintegration of the WAIS consensus. First, we provide a brief historical overview of scientific assessments of the WAIS. Second, we provide a detailed case study of the decision not to provide a WAIS prediction in the Fourth Assessment Report. Third, we discuss the implications of this outcome for the general issue of scientists and policymakers working in assessment organizations to make projections. IPCC authors were less certain about potential WAIS futures than in previous assessment reports in part because of new information, but also because of the outcome of cultural processes within the IPCC, including how people were selected for and worked together within their writing groups. It became too difficult for IPCC assessors to project the range of possible futures for WAIS due to shifts in scientific knowledge as well as in the institutions that facilitated the interpretations of this knowledge.
Feng, Shuaizhang, and Michael Oppenheimer. “Letter: Applying Statistical Models to the climate–migration Relationship.” PNAS Vol.109 (2012): E 2915. Print.
Oppenheimer, Michael. “Climate Change Impacts: Accounting for the Human Response.” Climatic Change Vol. 117 (2012): pp. 439–449. Print.
The assessment of potential impacts of climate change is progressing from taxonomies and enumeration of the magnitude of potential direct effects on individuals, societies, species, and ecosystems according to a limited number of metrics toward a more integrated approach that also encompasses the vast range of human response to experience and risk. Recent advances are both conceptual and methodological, and include analysis of some consequences of climate change that were heretofore intractable. In this article, I review a selection of these developments and represent them through a handful of illustrative cases. A key characteristic of the emerging areas of interest is a focus on understanding how human responses to direct impacts of climate change may cause important indirect and sometimes distant impacts. This realization underscores the need to develop integrated approaches for assessing and modeling impacts in an evolving socioeconomic and policy context.

2011

Katsman, Caroline A. et al. “Exploring High-End Scenarios for Local Sea Level Rise to Develop Flood Protection Strategies for a Low-Lying delta—the Netherlands As an Example.” Climatic Change Vol.109 (2011): pp. 617–645. Print.
Sea level rise, especially combined with possible changes in storm surges and increased river discharge resulting from climate change, poses a major threat in low-lying river deltas. In this study we focus on a specific example of such a delta: the Netherlands. To evaluate whether the country’s flood protection strategy is capable of coping with future climate conditions, an assessment of low-probability/high-impact scenarios is conducted, focusing mainly on sea level rise. We develop a plausible high-end scenario of 0.55 to 1.15 m global mean sea level rise, and 0.40 to 1.05 m rise on the coast of the Netherlands by 2100 (excluding land subsidence), and more than three times these local values by 2200. Together with projections for changes in storm surge height and peak river discharge, these scenarios depict a complex, enhanced flood risk for the Dutch delta.
Backstrand, Karin, James Meadowcroft, and Michael Oppenheimer. “The Politics and Policy of Carbon Capture and Storage : Framing an Emergent Technology.” Global Environmental Change vol.21.issue 2 (2011): pp. 275–281. Print.
O’Reilly, Jessica et al. “Characterizing Uncertainty in Expert Assessments: Ozone Depletion and the West Antarctic Ice Sheet.” WIREs Climate Change vol 2.issue 5 (2011): n. pag. Print.
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 a more complete evaluation of uncertainty. WIREs Clim Change 2011 2 728–743 DOI: 10.1002/wcc.135 This article is categorized under: Integrated Assessment of Climate Change > Integrated Assessment by Expert Panels
Yohe, Gary, and Michael Oppenheimer. “Evaluation, Characterization, and Communication of Uncertainty by the Intergovernmental Panel on Climate change—an Introductory Essay.” Climatic Change vol. 108 (2011): n. pag. Print.

2010

Turner, Will R. et al. “Climate Change: Helping Nature Survive the Human Response.” Conservation Letters vol 3 .issue 5 (2010): n. pag. Print.
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.
Gerber, Stefan et al. “Nitrogen Cycling and Feedbacks in a Global Dynamic Land Model.” Global Biogeochemical Cycles vol. 24.issue 1 (2010): n. pag. Print.
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–Geophysical Fluid Dynamic Laboratory (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 improve 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.
Ntelekos, Alexandros et al. “Urbanization, Climate Change and Flood Policy in the United States.” Climatic Change vol. 103 (2010): pp. 597–616. Print.
The average annual cost of floods in the United States has been estimated at about $2 billion (current US dollars). The federal government, through the creation of the National Flood Insurance Program (NFIP), has assumed responsibility for mitigating the societal and economic impacts of flooding by establishing a national policy that provides subsidized flood insurance. Increased flood costs during the past two decades have made the NFIP operate at a deficit. This paper argues that our current understanding of climate change and of the sensitivity of the urbanenvironmenttofloodscallforchangestothefloodpolicyscheme.Conclusions are drawn on specific examples from cities along the heavily urbanized corridor of northeastern United States. Mesoscale and global models along with urbanization and economic growth statistics are used to provide insights and recommendations for future flood costs under different emissions scenarios. Mesoscale modeling and future projections from global models suggest, for example, that under a high emissions scenario, New York City could experience almost twice as many days of extreme precipitation that cause flood damage and are disruptive to business as today. The results of the paper suggest that annual flood costs in the United States will increase sharply by the end of the 21st Century, ranging from about $7 to $19 billioncurrentUSdollars,dependingontheeconomicgrowthrateandtheemissions
Oppenheimer, Michael. “Climatic Change Letters: A Modest Effort to Address a Gigantic Problem.” Climatic Change vol 100 (2010): pp.7–10. Print.

For a full list of publications

Oppenheimer CV

Contact

Center for Policy Research on Energy and the Environment
Princeton School of Public and International Affairs
313 Robertson Hall
Princeton, NJ 08544
[email protected]

Assistant: Charles Crosby
[email protected]