Hot and Cold

Kevin Lewis

May 19, 2021

Temperature and outgroup discrimination
Donghyun Danny Choi, Mathias Poertner & Nicholas Sambanis
Political Science Research and Methods, forthcoming


High temperatures have been linked to aggression and different forms of conflict in humans. We consider whether exposure to heat waves increases discriminatory behavior toward outgroups. Using data from two large-scale field experiments in Germany, we find a direct causal effect of exposure to heat shocks on discrimination in helping behavior. As temperature rises, German natives faced with a choice to provide help to strangers in every-day interactions help Muslim immigrants less than they do other German natives, while help rates toward natives are unaffected by temperature. This finding suggests that there may be a physiological basis for discriminatory behavior toward outgroups.

The effect of information about climate risk on property values
Miyuki Hino & Marshall Burke
Proceedings of the National Academy of Sciences, 27 April 2021


Floods and other climate hazards pose a widespread and growing threat to housing and infrastructure around the world. By reflecting climate risk in prices, markets can discourage excessive development in hazardous areas. However, the extent to which markets price these risks remains poorly understood. Here we measure the effect of information about flood risk contained in regulatory floodplain maps on residential property values in the United States. Using multiple empirical approaches and two decades of sales data covering the universe of homes in the United States, we find little evidence that housing markets fully price information about flood risk in aggregate. However, the price penalty is larger for commercial buyers and in markets where buyers are more risk aware, suggesting that policies to improve risk communication could influence market outcomes. Our findings indicate that houses in flood zones in the United States are currently overvalued by a total of $43.8 billion (95% confidence interval: $32.6 to $55.6 billion) based on the information in publicly available flood hazard maps alone, raising concerns about the stability of real estate markets as climate risks become more salient and severe.

Thoughts on a Federal Government Stimulus Package for Buildings
Christoph Reinhart et al.
MIT Working Paper, April 2021


Residential buildings account for 22% of U.S. carbon emissions and there is widespread consensus that these carbon emissions can only be reduced if buildings become both more efficient and switch all of their fuel sources to electricity. We have developed an outline for an economic recovery package that would support energy retrofits for the 84 million detached single-family homes in the U.S. The goal of the program is to raise the nationwide retrofitting rate to 4% by 2030 so that all single-family homes will be retrofitted by 2050. It is assumed that market forces will self-sustain this 4% retrofitting rate after the program phases out. These retrofits, coupled with a decarbonizing power grid, would cut carbon emissions from U.S. residential homes up to 85% by 2050, leading to up to 11.5 billion tons of CO2 reductions and creating up to 265,000 long term clean tech jobs distributed across the nation. Estimated program costs would be up to $240 billion over ten years.

Assessing China’s efforts to pursue the 1.5°C warming limit
Hongbo Duan et al.
Science, 23 April 2021, Pages 378-385


Given the increasing interest in keeping global warming below 1.5°C, a key question is what this would mean for China’s emission pathway, energy restructuring, and decarbonization. By conducting a multimodel study, we find that the 1.5°C-consistent goal would require China to reduce its carbon emissions and energy consumption by more than 90 and 39%, respectively, compared with the “no policy” case. Negative emission technologies play an important role in achieving near-zero emissions, with captured carbon accounting on average for 20% of the total reductions in 2050. Our multimodel comparisons reveal large differences in necessary emission reductions across sectors, whereas what is consistent is that the power sector is required to achieve full decarbonization by 2050. The cross-model averages indicate that China’s accumulated policy costs may amount to 2.8 to 5.7% of its gross domestic product by 2050, given the 1.5°C warming limit.

The Paris Climate Agreement and future sea-level rise from Antarctica
Robert DeConto et al.
Nature, 6 May 2021, Pages 83–89


The Paris Agreement aims to limit global mean warming in the twenty-first century to less than 2 degrees Celsius above preindustrial levels, and to promote further efforts to limit warming to 1.5 degrees Celsius. The amount of greenhouse gas emissions in coming decades will be consequential for global mean sea level (GMSL) on century and longer timescales through a combination of ocean thermal expansion and loss of land ice. The Antarctic Ice Sheet (AIS) is Earth’s largest land ice reservoir (equivalent to 57.9 metres of GMSL), and its ice loss is accelerating. Extensive regions of the AIS are grounded below sea level and susceptible to dynamical instabilities that are capable of producing very rapid retreat. Yet the potential for the implementation of the Paris Agreement temperature targets to slow or stop the onset of these instabilities has not been directly tested with physics-based models. Here we use an observationally calibrated ice sheet–shelf model to show that with global warming limited to 2 degrees Celsius or less, Antarctic ice loss will continue at a pace similar to today’s throughout the twenty-first century. However, scenarios more consistent with current policies (allowing 3 degrees Celsius of warming) give an abrupt jump in the pace of Antarctic ice loss after around 2060, contributing about 0.5 centimetres GMSL rise per year by 2100 — an order of magnitude faster than today. More fossil-fuel-intensive scenarios9 result in even greater acceleration. Ice-sheet retreat initiated by the thinning and loss of buttressing ice shelves continues for centuries, regardless of bedrock and sea-level feedback mechanisms or geoengineered carbon dioxide reduction. These results demonstrate the possibility that rapid and unstoppable sea-level rise from Antarctica will be triggered if Paris Agreement targets are exceeded.

Time is of the Essence: Climate Adaptation Induced by Existing Institutions
Antonio Bento et al.
NBER Working Paper, May 2021


In the absence of first-best climate policy, we demonstrate that existing government institutions and policy established for reasons unrelated to climate change may induce climate adaptation. We examine the impact of temperature on ambient ozone concentration in the United States from 1980-2013, and the role of institution-induced adaptation. Ozone is formed under warm temperatures, and regulated by the Clean Air Act institution. Adaptation in counties out of attainment with air quality standards is 107 percent larger than under attainment, implying substantial institution-induced adaptation. Furthermore, local beliefs about climate change appear to reinforce adaptive behavior, suggesting a nontrivial role in second-best climate policy.

Expanding number of Western US urban centers face declining summertime air quality due to enhanced wildland fire activity
Kai Wilmot et al.
Environmental Research Letters, April 2021


Combining multiple sources of information on atmospheric composition, wildland fire emissions, and fire area burned, we link decadal air quality trends in Western US urban centers with wildland fire activity during the months of August and September for the years 2000–2019. We find spatially consistent trends in extreme levels (upper quantile) of fine particulate matter (PM2.5), organic carbon, and absorption aerosol optical depth centered on the US Pacific Northwest during the month of August. Emerging trends were also found across the Pacific Northwest, western Montana, and Wyoming in September. Furthermore, we identify potential wildfire emission 'hotspots' from trends in wildfire derived PM2.5 emissions and burned area. The spatial correspondence between wildfire emissions hotspots and extreme air quality trends, as well as their concomitant spatial shift from August to September supports the hypothesis that wildfires are driving extreme air quality trends across the Western US. We derive further evidence of the influence of wildland fires on air quality in Western US urban centers from smoke induced PM2.5 enhancements calculated through statistical modeling of the PM2.5-meteorology relationship at 18 Western US cities. Our results highlight the significant risk of increased human exposure to wildfire smoke in August at these Western US population centers, while also pointing to the potential danger of emerging trends in Western US population growth, wildfire emissions, and extreme air quality in September.

Accelerated global glacier mass loss in the early twenty-first century
Romain Hugonnet et al.
Nature, 29 April 2021, Pages 726–731


Glaciers distinct from the Greenland and Antarctic ice sheets are shrinking rapidly, altering regional hydrology, raising global sea level and elevating natural hazards. Yet, owing to the scarcity of constrained mass loss observations, glacier evolution during the satellite era is known only partially, as a geographic and temporal patchwork. Here we reveal the accelerated, albeit contrasting, patterns of glacier mass loss during the early twenty-first century. Using largely untapped satellite archives, we chart surface elevation changes at a high spatiotemporal resolution over all of Earth’s glaciers. We extensively validate our estimates against independent, high-precision measurements and present a globally complete and consistent estimate of glacier mass change. We show that during 2000–2019, glaciers lost a mass of 267 ± 16 gigatonnes per year, equivalent to 21 ± 3 per cent of the observed sea-level rise. We identify a mass loss acceleration of 48 ± 16 gigatonnes per year per decade, explaining 6 to 19 per cent of the observed acceleration of sea-level rise. Particularly, thinning rates of glaciers outside ice sheet peripheries doubled over the past two decades. Glaciers currently lose more mass, and at similar or larger acceleration rates, than the Greenland or Antarctic ice sheets taken separately. By uncovering the patterns of mass change in many regions, we find contrasting glacier fluctuations that agree with the decadal variability in precipitation and temperature. These include a North Atlantic anomaly of decelerated mass loss, a strongly accelerated loss from northwestern American glaciers, and the apparent end of the Karakoram anomaly of mass gain. We anticipate our highly resolved estimates to advance the understanding of drivers that govern the distribution of glacier change, and to extend our capabilities of predicting these changes at all scales. Predictions robustly benchmarked against observations are critically needed to design adaptive policies for the local- and regional-scale management of water resources and cryospheric risks, as well as for the global-scale mitigation of sea-level rise.

Policy Feedback and Interdependence in American Federalism: Evidence from Rooftop Solar Politics
Samuel Trachtman
Perspectives on Politics, forthcoming


Scholars have long understood the American states as “laboratories of democracy,” exploring how mechanisms of learning and competition lead to the diffusion of successful state policy experiments across the federal system. Drawing from policy feedback literature, I develop a new framework for studying policy interdependence in American federalism. I argue that state policies can, in addition to promoting learning and competition, also feed into the interest group politics in other states. Broadly speaking, the organized interests that benefit from, and are strengthened by, particular policy reforms might apply newfound strength to propagate them. Empirically, I study rooftop solar policy, an area in which state-level decisions have been fundamental to industry growth and the emergence of installers as political actors. Bringing together a variety of administrative, lobbying, and policy data, I demonstrate that solar installers used resources accumulated in early adopter of favorable rooftop solar policies to influence policy decisions elsewhere. For reformers, I suggest that subnational policy can be a crucial ingredient in building coalitions for (geographically) broader policy reform.

Carbon loss from forest degradation exceeds that from deforestation in the Brazilian Amazon
Yuanwei Qin et al.
Nature Climate Change, May 2021, Pages 442–448


Spatial–temporal dynamics of aboveground biomass (AGB) and forest area affect the carbon cycle, climate and biodiversity in the Brazilian Amazon. Here we investigate interannual changes in AGB and forest area by analysing satellite-based annual AGB and forest area datasets. We found that the gross forest area loss was larger in 2019 than in 2015, possibly due to recent loosening of forest protection policies. However, the net AGB loss was three times smaller in 2019 than in 2015. During 2010–2019, the Brazilian Amazon had a cumulative gross loss of 4.45 Pg C against a gross gain of 3.78 Pg C, resulting in a net AGB loss of 0.67 Pg C. Forest degradation (73%) contributed three times more to the gross AGB loss than deforestation (27%), given that the areal extent of degradation exceeds that of deforestation. This indicates that forest degradation has become the largest process driving carbon loss and should become a higher policy priority.

Polar Drift in the 1990s Explained by Terrestrial Water Storage Changes
Shanshan Deng et al.
Geophysical Research Letters, 16 April 2021


Secular polar drift underwent a directional change in the 1990s, but the underlying mechanism remains unclear. In this study, polar motion observations are compared with geophysical excitations from the atmosphere, oceans, solid Earth, and terrestrial water storage (TWS) during the period of 1981–2020 to determine major drivers. When contributions from the atmosphere, oceans, and solid Earth are removed, the residual dominates the change in the 1990s. The contribution of TWS to the residual is quantified by comparing the hydrological excitations from modeled TWS changes in two different scenarios. One scenario assumes that the TWS change is stationary over the entire study period, and another scenario corrects the stationary result with actual glacier mass change. The accelerated ice melting over major glacial areas drives the polar drift toward 26°E for 3.28 mas/yr after the 1990s. The findings offer a clue for studying past climate‐driven polar motion.


from the


A weekly newsletter with free essays from past issues of National Affairs and The Public Interest that shed light on the week's pressing issues.


to your National Affairs subscriber account.

Already a subscriber? Activate your account.


Unlimited access to intelligent essays on the nation’s affairs.

Subscribe to National Affairs.