Kevin Lewis

June 07, 2017

Public opinion on climate change: Is there an economy–environment tradeoff?
Matto Mildenberger & Anthony Leiserowitz
Environmental Politics, forthcoming


Does the state of the economy condition public concern for the environment? Scholars have long argued that environmental preferences decline during economic downturns as individuals prioritize short-term economic needs over longer-term environmental concerns. Yet, this assumption has rarely been subjected to rigorous empirical scrutiny at the individual level. The presumed link between economic and environmental preferences is revisited, using the first individual-level opinion panel (n = 1043) of US climate attitudes, incorporating both self-reported and objective economic data. In contrast with prior studies that emphasize the role of economic downturns in driving environmental preference shifts, using a stronger identification strategy, there is little evidence that changes in either individual economic fortunes or local economic conditions are associated with decreased belief that climate change is happening or reduced prioritization of climate policy action. Instead, the evidence suggests that climate belief declines are associated with shifting political cues. These findings have important implications for understanding the dynamics of political conflict over environmental policy globally.

Nighttime temperature and human sleep loss in a changing climate
Nick Obradovich et al.
Science Advances, May 2017


Human sleep is highly regulated by temperature. Might climate change — through increases in nighttime heat — disrupt sleep in the future? We conduct the inaugural investigation of the relationship between climatic anomalies, reports of insufficient sleep, and projected climate change. Using data from 765,000 U.S. survey respondents from 2002 to 2011, coupled with nighttime temperature data, we show that increases in nighttime temperatures amplify self-reported nights of insufficient sleep. We observe the largest effects during the summer and among both lower-income and elderly respondents. We combine our historical estimates with climate model projections and detail the potential sleep impacts of future climatic changes. Our study represents the largest ever investigation of the relationship between sleep and ambient temperature and provides the first evidence that climate change may disrupt human sleep.

Bill McKibben's Effect on the US Climate Change Debate: Shifting the Institutional Environment Through Radical Flank Effects
Todd Schifeling & Andrew John Hoffman
University of Michigan Working Paper, April 2017


This paper investigates the presence and influence of radical flanks on field-level debates. We study the ability of radical flank actors to shift the focus of these debates by increasing the legitimacy of pre-existing but peripheral issues. We apply this conceptual model to the empirical context of the climate change debate in the United States and the efforts of Bill McKibben and to pressure major Universities and Colleges to divest their financial investments in fossil fuel assets. As these new actors and issue entered the debate, we find that, while divestment itself gained limited traction, liberal policy ideas, which had previously been marginalized in the U.S. debate, gained increased attention and legitimacy. Using network text analysis, this paper expands theories of how social movements affect organizational fields through a discursive radical flank mechanism while also illuminating key dynamics in climate change politics.

The Impact on Global Greenhouse Gas Emissions of Geographic Shifts in Global Supply Chains
Xuemei Jiang & Christopher Green
Ecological Economics, September 2017, Pages 102–114


During the past two decades there has been a shift in the geography of Global Supply Chains (GSCs) from developed countries to China, and more recently from China to successor developing countries in South Asia, Africa and Latin America. The shift in GSC geography influences global greenhouse gas (GHG) emissions because of an energy efficiency and low-carbon technology gap between developed and developing economies. Our simulations indicate that changing GSC geography toward China positively contributed, on average (2001–2008), 919 Mt CO2 equivalents to global GHG emissions annually. In addition, there are potentially even larger indirect effects, including import-related and transportation-related emissions that are attributable to GSC shift-related improvements in developing world consumption and infrastructure. We then investigate the emission impact of a further GSCs shift toward South Asia, Africa and Latin America. Although the direct impact of such a shift is likely negative due to a lower dependency on coal as well as lower carbon intensities in South Asia, Africa and Latin America relative to China, it is likely that the direct effects are more than offset by the indirect shift-related effects associated with improvements in consumption and infrastructure. Our results have policy implications for future climate change mitigation.

Economic Effectiveness of Implementing a Statewide Building Code: The Case of Florida
Kevin Simmons, Jeffrey Czajkowski & James Done
University of Pennsylvania Working Paper, May 2017


Hurricane Andrew revealed inadequate construction practices were utilized in Florida for decades. In response, Florida adopted a new statewide code – the 2001 Florida Building Code (FBC) which became one of the strictest in the nation. We use ten years of insured loss data to show that the FBC reduced windstorm losses by up to 72%, then use our results to conduct a benefit-cost analysis (BCA). The FBC passes the BCA by a margin of 5 dollars in reduced loss to 1 dollar of added cost, with a payback period of approximately 10 years.

Global temperature evolution: Recent trends and some pitfalls
Stefan Rahmstorf, Grant Foster & Niamh Cahill
Environmental Research Letters, May 2017


Global surface temperatures continue to rise. In most surface temperature data sets, the years 2014, 2015 and again 2016 set new global heat records since the start of regular measurements. Never before have three record years occurred in a row. We show that this recent streak of record heat does not in itself provide statistical evidence for an acceleration of global warming, nor was it preceded by a 'slowdown period' with a significantly reduced rate of warming. Rather, the data are fully consistent with a steady global warming trend since the 1970s, superimposed with random, stationary, short-term variability. All recent variations in short-term trends are well within what was to be expected, based on the observed warming trend and the observed variability from the 1970s up to the year 2000. We discuss some pitfalls of statistical analysis of global temperatures which have led to incorrect claims of an unexpected or significant warming slowdown.

Reassessment of 20th century global mean sea level rise
Sönke Dangendorf et al.
Proceedings of the National Academy of Sciences, 6 June 2017, Pages 5946–5951


The rate at which global mean sea level (GMSL) rose during the 20th century is uncertain, with little consensus between various reconstructions that indicate rates of rise ranging from 1.3 to 2 mm⋅y−1. Here we present a 20th-century GMSL reconstruction computed using an area-weighting technique for averaging tide gauge records that both incorporates up-to-date observations of vertical land motion (VLM) and corrections for local geoid changes resulting from ice melting and terrestrial freshwater storage and allows for the identification of possible differences compared with earlier attempts. Our reconstructed GMSL trend of 1.1 ± 0.3 mm⋅y−1 (1σ) before 1990 falls below previous estimates, whereas our estimate of 3.1 ± 1.4 mm⋅y−1 from 1993 to 2012 is consistent with independent estimates from satellite altimetry, leading to overall acceleration larger than previously suggested. This feature is geographically dominated by the Indian Ocean–Southern Pacific region, marking a transition from lower-than-average rates before 1990 toward unprecedented high rates in recent decades. We demonstrate that VLM corrections, area weighting, and our use of a common reference datum for tide gauges may explain the lower rates compared with earlier GMSL estimates in approximately equal proportion. The trends and multidecadal variability of our GMSL curve also compare well to the sum of individual contributions obtained from historical outputs of the Coupled Model Intercomparison Project Phase 5. This, in turn, increases our confidence in process-based projections presented in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.

Australian climate extremes at 1.5 °C and 2 °C of global warming
Andrew King, David Karoly & Benjamin Henley
Nature Climate Change, June 2017, Pages 412–416


To avoid more severe impacts from climate change, there is international agreement to strive to limit warming to below 1.5 °C. However, there is a lack of literature assessing climate change at 1.5 °C and the potential benefits in terms of reduced frequency of extreme events. Here, we demonstrate that existing model simulations provide a basis for rapid and rigorous analysis of the effects of different levels of warming on large-scale climate extremes, using Australia as a case study. We show that limiting warming to 1.5 °C, relative to 2 °C, would perceptibly reduce the frequency of extreme heat events in Australia. The Australian continent experiences a variety of high-impact climate extremes that result in loss of life, and economic and environmental damage. Events similar to the record-hot summer of 2012–2013 and warm seas associated with bleaching of the Great Barrier Reef in 2016 would be substantially less likely, by about 25% in both cases, if warming is kept to lower levels. The benefits of limiting warming on hydrometeorological extremes are less clear. This study provides a framework for analysing climate extremes at 1.5 °C global warming.

The limits to global-warming mitigation by terrestrial carbon removal
Lena Boysen et al.
Earth's Future, forthcoming


Massive near-term greenhouse gas emissions reduction is a precondition for staying “well below 2°C” global warming as envisaged by the Paris Agreement. Furthermore, extensive terrestrial carbon dioxide removal (tCDR) through managed biomass growth and subsequent carbon capture and storage is required to avoid temperature “overshoot” in most pertinent scenarios. Here, we address two major issues: First, we calculate the extent of tCDR required to “repair” delayed or insufficient emissions reduction policies unable to prevent global mean temperature rise of 2.5°C or even 4.5°C above pre-industrial level. Our results show that those tCDR measures are unable to counteract “business-as-usual” emissions without eliminating virtually all natural ecosystems. Even if considerable (Representative Concentration Pathway 4.5 [RCP4.5]) emissions reductions are assumed, tCDR with 50% storage efficiency requires >1.1 Gha of the most productive agricultural areas or the elimination of >50% of natural forests. In addition, >100 MtN/yr fertilizers would be needed to remove the roughly 320 GtC foreseen in these scenarios. Such interventions would severely compromise food production and/or biosphere functioning. Second, we reanalyze the requirements for achieving the 160–190 GtC tCDR that would complement strong mitigation action (RCP2.6) in order to avoid 2°C overshoot anytime. We find that a combination of high irrigation water input and/or more efficient conversion to stored carbon is necessary. In the face of severe trade-offs with society and the biosphere, we conclude that large-scale tCDR is not a viable alternative to aggressive emissions reduction. However, we argue that tCDR might serve as a valuable “supporting actor” for strong mitigation if sustainable schemes are established immediately.

Connections between north-central United States summer hydroclimatology and Arctic sea ice variability
Dagmar Budikova, Trent Ford & Thomas Ballinger
International Journal of Climatology, forthcoming


Arctic sea ice has been shrinking at unprecedented rates over the past three decades. These cryospheric changes have coincided with greater incidence of global extreme weather conditions, including increased severity and frequency of summer heatwaves and extreme rainfall events. Recent studies identify potential physical mechanisms related to Rossby wave and resonance theories that may attribute the observed changes in extreme summer weather patterns to Arctic sea ice decline. This study explores the linkages between summer Arctic sea ice variability and hydroclimate of the north-central United States (US) during the 1979 to 2013 period. Since 1979, summers with low sea ice conditions have coincided with significant increases in mean, minimum, maximum, and dew point air temperatures. Also apparent are increases in seasonal precipitation, the number of wet days, heavy (>95th percentile) precipitation days, and accumulated precipitation over the region. These moisture changes coincide with atmospheric patterns typically observed during anomalously wet summers, known to prompt flooding across the Upper Mississippi River Valley (UMRV) region. Low sea ice summers have coincided with (1) enhanced southerly air flow and increased activity of the Great Plains Low Level Jet (GPLLJ) over the study area, (2) increased occurrence of moist tropical air masses over the UMRV region, and (3) amplified 500 hPa flow over the Pacific-North American region with a ridge situated over the central-eastern portions of the North American continent emanating from Greenland and the central Arctic basin. The results suggest summer Arctic sea ice variability has been associated with recent hydroclimate anomalies of the north-central United States and the UMRV region and add to our growing knowledge of the connections between a changing Arctic environment and concurrent mid-latitude climate variability.

Drylands face potential threat under 2 °C global warming target
Jianping Huang et al.
Nature Climate Change, June 2017, Pages 417–422


The Paris Agreement aims to limit global mean surface warming to less than 2 °C relative to pre-industrial levels. However, we show this target is acceptable only for humid lands, whereas drylands will bear greater warming risks. Over the past century, surface warming over global drylands (1.2–1.3 °C) has been 20–40% higher than that over humid lands (0.8–1.0 °C), while anthropogenic CO2 emissions generated from drylands (~230 Gt) have been only ~30% of those generated from humid lands (~750 Gt). For the twenty-first century, warming of 3.2–4.0 °C (2.4–2.6 °C) over drylands (humid lands) could occur when global warming reaches 2.0 °C, indicating ~44% more warming over drylands than humid lands. Decreased maize yields and runoff, increased long-lasting drought and more favourable conditions for malaria transmission are greatest over drylands if global warming were to rise from 1.5 °C to 2.0 °C. Our analyses indicate that ~38% of the world’s population living in drylands would suffer the effects of climate change due to emissions primarily from humid lands. If the 1.5 °C warming limit were attained, the mean warming over drylands could be within 3.0 °C; therefore it is necessary to keep global warming within 1.5 °C to prevent disastrous effects over drylands.

Consequences of rapid ice sheet melting on the Sahelian population vulnerability
Dimitri Defrance et al.
Proceedings of the National Academy of Sciences, forthcoming


The acceleration of ice sheet melting has been observed over the last few decades. Recent observations and modeling studies have suggested that the ice sheet contribution to future sea level rise could have been underestimated in the latest Intergovernmental Panel on Climate Change report. The ensuing freshwater discharge coming from ice sheets could have significant impacts on global climate, and especially on the vulnerable tropical areas. During the last glacial/deglacial period, megadrought episodes were observed in the Sahel region at the time of massive iceberg surges, leading to large freshwater discharges. In the future, such episodes have the potential to induce a drastic destabilization of the Sahelian agroecosystem. Using a climate modeling approach, we investigate this issue by superimposing on the Representative Concentration Pathways 8.5 (RCP8.5) baseline experiment a Greenland flash melting scenario corresponding to an additional sea level rise ranging from 0.5 m to 3 m. Our model response to freshwater discharge coming from Greenland melting reveals a significant decrease of the West African monsoon rainfall, leading to changes in agricultural practices. Combined with a strong population increase, described by different demography projections, important human migration flows could be potentially induced. We estimate that, without any adaptation measures, tens to hundreds million people could be forced to leave the Sahel by the end of this century. On top of this quantification, the sea level rise impact over coastal areas has to be superimposed, implying that the Sahel population could be strongly at threat in case of rapid Greenland melting.

Boosted food web productivity through ocean acidification collapses under warming
Silvan Goldenberg et al.
Global Change Biology, forthcoming


Future climate is forecast to drive bottom-up (resource driven) and top-down (consumer driven) change to food web dynamics and community structure. Yet, our predictive understanding of these changes is hampered by an over-reliance on simplified laboratory systems centred on single trophic levels. Using a large mesocosm experiment, we reveal how future ocean acidification and warming modify trophic linkages across a three-level food web: that is, primary (algae), secondary (herbivorous invertebrates) and tertiary (predatory fish) producers. Both elevated CO2 and elevated temperature boosted primary production. Under elevated CO2, the enhanced bottom-up forcing propagated through all trophic levels. Elevated temperature, however, negated the benefits of elevated CO2 by stalling secondary production. This imbalance caused secondary producer populations to decline as elevated temperature drove predators to consume their prey more rapidly in the face of higher metabolic demand. Our findings demonstrate how anthropogenic CO2 can function as a resource that boosts productivity throughout food webs, and how warming can reverse this effect by acting as a stressor to trophic interactions. Understanding the shifting balance between the propagation of resource enrichment and its consumption across trophic levels provides a predictive understanding of future dynamics of stability and collapse in food webs and fisheries production.

Climate mitigation from vegetation biophysical feedbacks during the past three decades
Zhenzhong Zeng et al.
Nature Climate Change, July 2017, Pages 432–436


The surface air temperature response to vegetation changes has been studied for the extreme case of land-cover change; yet, it has never been quantified for the slow but persistent increase in leaf area index (LAI) observed over the past 30 years (Earth greening). Here we isolate the fingerprint of increasing LAI on surface air temperature using a coupled land–atmosphere global climate model prescribed with satellite LAI observations. We find that the global greening has slowed down the rise in global land-surface air temperature by 0.09 ± 0.02 °C since 1982. This net cooling effect is the sum of cooling from increased evapotranspiration (70%), changed atmospheric circulation (44%), decreased shortwave transmissivity (21%), and warming from increased longwave air emissivity (−29%) and decreased albedo (−6%). The global cooling originated from the regions where LAI has increased, including boreal Eurasia, Europe, India, northwest Amazonia, and the Sahel. Increasing LAI did not, however, significantly change surface air temperature in eastern North America and East Asia, where the effects of large-scale atmospheric circulation changes mask local vegetation feedbacks. Overall, the sum of biophysical feedbacks related to the greening of the Earth mitigated 12% of global land-surface warming for the past 30 years.

Benefits and Ancillary Costs of Natural Infrastructure: Evidence from the New Jersey Coast
Steven Dundas
Journal of Environmental Economics and Management, September 2017, Pages 62–80


This paper empirically estimates the economic impacts of a large-scale public investment in natural infrastructure aimed at adapting to climate change and increasing coastal resilience. I utilize temporal and spatial variation in investment in dunes to provide a hedonic property value estimate of the economic benefits. I identify the net effect of treatment utilizing the doubly robust Oaxaca-Blinder estimator and show that coastal housing price increases attributable to constructed dunes are approximately 3.6 percent. A decomposition of the average impact suggests that the policy intervention generates ancillary costs related to impaired ocean views and privacy concerns that partially offset large protection benefits.

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