Hot Topics

Kevin Lewis

June 10, 2020

Supply Chain Linkages and the Extended Carbon Coalition
Jared Cory, Michael Lerner & Iain Osgood
American Journal of Political Science, forthcoming


Which firms oppose action to fight climate change? Networks of input sourcing and sales to downstream customers ought to propagate and reinforce opposition to decarbonization beyond direct emitters of CO2. To test this claim, we build the largest data set of public political activity for and against climate action in the United States, revealing that the majority of corporate opposition to climate action comes from outside the highest‐emitting industries. We construct new measures of the carbon intensity of firms and show that policy exposure via carbon‐intensive inputs and sales to downstream emitters explains this large volume of opposition from non‐emitting industries. Sixty‐six percent of U.S. lobbying on climate policy has been conducted by an extended coalition of firms, associations, and other groups that have publicly opposed reducing carbon emissions. Public opposition to climate action by carbon‐connected industries is therefore broad‐based, highly organized, and matched with extensive lobbying.

Does Climate Protest Work? Partisanship, Protest, and Sentiment Pools
Dylan Bugden
Socius: Sociological Research for a Dynamic World, May 2020


This study demonstrates whether and how climate protest increases or decreases the “sentiment pools” available to the climate movement. Using an experimental vignette survey design (n = 1,421), the author finds that compared with a control condition, peaceful marches are effective for both independents and Democrats, while civil disobedience has a positive effect among Democrats. These effects are isolated to those who are most certain of anthropogenic climate change. No effect is observed among Republicans. Despite evidence from other studies suggesting the possibility, no “backfire” effects are observed for any group or protest type. This study (1) lends supports to the use of tactical diversity within the climate movement and (2) demonstrates how the broader forces of partisanship interact with protest to shift the pool of supporters available to movements, extending our nascent collective knowledge of how partisanship shapes the outcomes of social movements and protest.

The emergence of heat and humidity too severe for human tolerance
Colin Raymond, Tom Matthews & Radley Horton
Science Advances, May 2020


Humans’ ability to efficiently shed heat has enabled us to range over every continent, but a wet-bulb temperature (TW) of 35°C marks our upper physiological limit, and much lower values have serious health and productivity impacts. Climate models project the first 35°C TW occurrences by the mid-21st century. However, a comprehensive evaluation of weather station data shows that some coastal subtropical locations have already reported a TW of 35°C and that extreme humid heat overall has more than doubled in frequency since 1979. Recent exceedances of 35°C in global maximum sea surface temperature provide further support for the validity of these dangerously high TW values. We find the most extreme humid heat is highly localized in both space and time and is correspondingly substantially underestimated in reanalysis products. Our findings thus underscore the serious challenge posed by humid heat that is more intense than previously reported and increasingly severe.

The Food Problem and the Aggregate Productivity Consequences of Climate Change
Ishan Nath
NBER Working Paper, June 2020


This paper integrates local temperature treatment effects and a quantitative macroeconomic model to evaluate the impact of climate change on sectoral reallocation and aggregate productivity. First, I use firm-level data from a wide range of countries to estimate the effect of temperature on productivity in manufacturing and services. Estimates suggest that extreme heat reduces non-agricultural productivity, but less so than in agriculture, implying that hot countries could adapt to climate change by importing food and shifting labor toward manufacturing. Second, I embed my estimates in an open-economy model of structural transformation covering 158 countries to investigate this possibility. Simulations suggest that subsistence food requirements drive agricultural specialization more than comparative advantage, however, such that climate change perversely pulls labor into agriculture where its productivity suffers most and reallocation exacerbates the global decline in GDP. The productivity effects of climate change reduce welfare by 1.5-2.7% overall and 6-10% for the poorest quartile. Trade reduces the welfare costs of climate change by only 7.4% under existing policy, but by 31% overall and 68% for the global poor in a counterfactual scenario that assigns all countries the 90th percentile level of trade openness.

Climate and health damages from global concrete production
Sabbie Miller & Frances Moore
Nature Climate Change, May 2020, Pages 439–443


Growing infrastructure needs worldwide have created an unprecedented demand for concrete. Its production results in high GHG emissions, the primary focus of research and mitigation strategies in the sector. However, emissions of air pollutants and the economic burden of resultant health consequences are not yet known. Here, we show worldwide concrete production contributes approximately 7.8% of nitrogen oxide emissions, 4.8% of sulfur oxide emissions, 5.2% of particulate matter emissions smaller than 10 microns and 6.4% of particulate emissions smaller than 2.5 microns. Economic valuation of the damages from these and GHG emissions total ~75% of the cement and concrete industry current value. Commonly discussed GHG emissions mitigation strategies can halve these costs but, under certain scenarios, may increase local air pollution and associated health damages. These findings highlight potential synergies and trade-offs between GHG mitigation and improvements in local air quality, with implications for the political feasibility of different mitigation options.

The economic costs of Hurricane Harvey attributable to climate change
David Frame et al.
Climatic Change, May 2020, Pages 271–281


Hurricane Harvey is one of the costliest tropical cyclones in history. In this paper, we use a probabilistic event attribution framework to estimate the costs associated with Hurricane Harvey that are attributable to anthropogenic influence on the climate system. Results indicate that the “fraction of attributable risk” for the rainfall from Harvey was likely about at least a third with a preferable/best estimate of three quarters. With an average estimate of damages from Harvey assessed at about US$90bn, applying this fraction gives a best estimate of US$67bn, with a likely lower bound of at least US$30bn, of these damages that are attributable to the human influence on climate. This “bottom-up” event-based estimate of climate change damages contrasts sharply with the more “top-down” approach using integrated assessment models (IAMs) or global macroeconometric estimates: one IAM estimates annual climate change damages in the USA to be in the region of US$21.3bn. While the two approaches are not easily comparable, it is noteworthy that our “bottom-up” results estimate that one single extreme weather event contributes more to climate change damages in the USA than an entire year by the “top-down” method. Given that the “top-down” approach, at best, parameterizes but does not resolve the effects of extreme weather events, our findings suggest that the “bottom-up” approach is a useful avenue to pursue in future attempts to refine estimates of climate change damages.

Reduced frequency and size of late-twenty-first-century snowstorms over North America
Walker Ashley, Alex Haberlie & Vittorio Gensini
Nature Climate Change, June 2020, Pages 539–544


Understanding how snowstorms may change in the future is critical for estimating impacts on water resources and the Earth and socioeconomic systems that depend on them. Here we use snowstorms as a marker to assess the mesoscale fingerprint of climate change, providing a description of potential changes in winter weather event occurrence, character and variability in central and eastern North America under a high anthropogenic emissions pathway. Snowstorms are segmented and tracked using high-resolution, snow water equivalent output from dynamically downscaled simulations which, unlike global climate models, can resolve important mesoscale features such as banded snow. Significant decreases are found in the frequency and size of snowstorms in a pseudo-global warming simulation, including those events that produce the most extreme snowfall accumulations. Early and late boreal winter months show particularly robust proportional decreases in snowstorms and snow water equivalent accumulations.

Estimating US fossil fuel CO2 emissions from measurements of 14C in atmospheric CO2
Sourish Basu et al.
Proceedings of the National Academy of Sciences, forthcoming


We report national scale estimates of CO2 emissions from fossil-fuel combustion and cement production in the United States based directly on atmospheric observations, using a dual-tracer inverse modeling framework and CO2 and Δ14CO2 measurements obtained primarily from the North American portion of the National Oceanic and Atmospheric Administration’s Global Greenhouse Gas Reference Network. The derived US national total for 2010 is 1,653 ± 30 TgC yr−1 with an uncertainty (1σ) that takes into account random errors associated with atmospheric transport, atmospheric measurements, and specified prior CO2 and 14C fluxes. The atmosphere-derived estimate is significantly larger (>3σ) than US national emissions for 2010 from three global inventories widely used for CO2 accounting, even after adjustments for emissions that might be sensed by the atmospheric network, but which are not included in inventory totals. It is also larger (>2σ) than a similarly adjusted total from the US Environmental Protection Agency (EPA), but overlaps EPA’s reported upper 95% confidence limit. In contrast, the atmosphere-derived estimate is within 1σ of the adjusted 2010 annual total and nine of 12 adjusted monthly totals aggregated from the latest version of the high-resolution, US-specific “Vulcan” emission data product. Derived emissions appear to be robust to a range of assumed prior emissions and other parameters of the inversion framework. While we cannot rule out a possible bias from assumed prior Net Ecosystem Exchange over North America, we show that this can be overcome with additional Δ14CO2 measurements. These results indicate the strong potential for quantification of US emissions and their multiyear trends from atmospheric observations.

A Spatially Variable Time Series of Sea Level Change Due to Artificial Water Impoundment
William Hawley et al.
Earth's Future, forthcoming


The artificial impoundment of water behind dams causes global mean sea level (GMSL) to fall as reservoirs fill, but also generates a local rise in sea level due to the increased mass in the reservoir and the crustal deformation this mass induces. To estimate spatiotemporal fluctuations in sea level due to water impoundment, we use a historical data set that includes 6,329 reservoirs completed between 1900 and 2011, as well as projections of 3,565 reservoirs that are expected to be completed by 2040. The GMSL change associated with the historical data (–0.2 mm yr‐1 from 1900 – 2011) is consistent with previous studies, but the temporal and spatial resolution allows for local studies that were not previously possible, revealing that some locations experience a sea level rise of as much as 40 mm over less than a decade. Future construction of reservoirs through ~2040 is projected to cause a GMSL fall whose rate is comparable to that of the last century (–0.3 mm yr‐1), but with a geographic distribution that will be distinct from the last century, including a rise in sea level in more coastal areas. The analysis of expected construction shows that significant impoundment near coastal communities in the coming decades could enhance the flooding risk already heightened by global sea level rise.

Precipitation Modification by Ionization
Giles Harrison et al.
Physical Review Letters, May 2020


Rainfall is hypothesized to be influenced by droplet charge, which is related to the global circuit current flowing through clouds. This is tested through examining a major global circuit current increase following the release of artificial radioactivity. Significant changes occurred in daily rainfall distribution in the Shetland Islands, away from pollution. Daily rainfall changed by 24%, and local clouds optically thickened, within the nuclear weapons test period. This supports expectations of electrically induced microphysical changes in liquid water clouds from additional ionization.

Cenozoic sea-level and cryospheric evolution from deep-sea geochemical and continental margin records
Kenneth Miller et al.
Science Advances, May 2020


Using Pacific benthic foraminiferal δ18O and Mg/Ca records, we derive a Cenozoic (66 Ma) global mean sea level (GMSL) estimate that records evolution from an ice-free Early Eocene to Quaternary bipolar ice sheets. These GMSL estimates are statistically similar to “backstripped” estimates from continental margins accounting for compaction, loading, and thermal subsidence. Peak warmth, elevated GMSL, high CO2, and ice-free “Hothouse” conditions (56 to 48 Ma) were followed by “Cool Greenhouse” (48 to 34 Ma) ice sheets (10 to 30 m changes). Continental-scale ice sheets (“Icehouse”) began ~34 Ma (>50 m changes), permanent East Antarctic ice sheets at 12.8 Ma, and bipolar glaciation at 2.5 Ma. The largest GMSL fall (27 to 20 ka; ~130 m) was followed by a >40 mm/yr rise (19 to 10 ka), a slowing (10 to 2 ka), and a stillstand until ~1900 CE, when rates began to rise. High long-term CO2 caused warm climates and high sea levels, with sea-level variability dominated by periodic Milankovitch cycles.

Human influence has intensified extreme precipitation in North America
Megan Kirchmeier-Young & Xuebin Zhang
Proceedings of the National Academy of Sciences, forthcoming


Precipitation extremes have implications for many facets of both the human and natural systems, predominantly through flooding events. Observations have demonstrated increasing trends in extreme precipitation in North America, and models and theory consistently suggest continued increases with future warming. Here, we address the question of whether observed changes in annual maximum 1- and 5-d precipitation can be attributed to human influence on the climate. Although attribution has been demonstrated for global and hemispheric scales, there are few results for continental and subcontinental scales. We utilize three large ensembles, including simulations from both a fully coupled Earth system model and a regional climate model. We use two different attribution approaches and find many qualitatively consistent results across different methods, different models, and different regional scales. We conclude that external forcing, dominated by human influence, has contributed to the increase in frequency and intensity of regional precipitation extremes in North America. If human emissions continue to increase, North America will see further increases in these extremes.

External Forcing Explains Recent Decadal Variability of the Ocean Carbon Sink
Galen McKinley et al.
AGU Advances, June 2020


The ocean has absorbed the equivalent of 39% of industrial‐age fossil carbon emissions, significantly modulating the growth rate of atmospheric CO2 and its associated impacts on climate. Despite the importance of the ocean carbon sink to climate, our understanding of the causes of its interannual‐to‐decadal variability remains limited. This hinders our ability to attribute its past behavior and project its future. A key period of interest is the 1990s, when the ocean carbon sink did not grow as expected. Previous explanations of this behavior have focused on variability internal to the ocean or associated with coupled atmosphere/ocean modes. Here, we use an idealized upper ocean box model to illustrate that two external forcings are sufficient to explain the pattern and magnitude of sink variability since the mid‐1980s. First, the global‐scale reduction in the decadal‐average ocean carbon sink in the 1990s is attributable to the slowed growth rate of atmospheric pCO2. The acceleration of atmospheric pCO2 growth after 2001 drove recovery of the sink. Second, the global sea surface temperature response to the 1991 eruption of Mt Pinatubo explains the timing of the global sink within the 1990s. These results are consistent with previous experiments using ocean hindcast models with variable atmospheric pCO2 and with and without climate variability. The fact that variability in the growth rate of atmospheric pCO2 directly imprints on the ocean sink implies that there will be an immediate reduction in ocean carbon uptake as atmospheric pCO2 responds to cuts in anthropogenic emissions.

Arctic freshwater fish productivity and colonization increase with climate warming
Steven Campana et al.
Nature Climate Change, May 2020, Pages 428–433


Climate warming at high latitudes has long been expected to exceed that predicted for tropical and temperate climes, but recent warming in the Arctic has exceeded even those expectations1. The geophysical consequences of this warming are reasonably well established2, but the impacts on freshwater fauna are poorly understood. Here we use a large-scale geospatial analysis of the population dynamics of one of the most abundant north temperate freshwater fish species to forecast increased demographic rates, productivity and colonization range in response to IPCC climate warming scenarios. Geospatial lake morphometry data were used to characterize 481,784 lakes in the Canadian Arctic capable of supporting lake trout (Salvelinus namaycush) populations. Lake trout productivity in existing habitat is projected to increase by 20% by 2050 due to climate change, but an expanded habitable zone may result in a 29% increase in harvestable biomass. Although many ecosystems are likely to be negatively impacted by climate warming, the phenotypic plasticity of fish will allow a rapid relaxation of the current environmental constraints on growth in the far north, as well as enhanced colonization of bodies of water in which there are few potential competitors.


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