Climate of fear
Marshall Burke, Solomon Hsiang & Edward Miguel
NBER Working Paper, October 2014
Abstract:
Until recently, neither climate nor conflict have been core areas of inquiry within economics, but there has been an explosion of research on both topics in the past decade, with a particularly large body of research emerging at their intersection. In this review, we survey this literature on the interlinkages between climate and conflict, by necessity drawing from both economics and other disciplines given the inherent interdisciplinarity of research in this field. We consider many types of human conflict in the review, including both interpersonal conflict — such as domestic violence, road rage, assault, murder, and rape — and intergroup conflict — including riots, ethnic violence, land invasions, gang violence, civil war and other forms of political instability, such as coups. We discuss the key methodological issues in estimating causal relationships in this area, and largely focus on "natural experiments" that exploit variation in climate variables over time, helping to address omitted variable bias concerns. After harmonizing statistical specifications and standardizing estimated effect sizes within each conflict category, we carry out a hierarchical meta-analysis that allows us to estimate the mean effect of climate variation on conflict outcomes as well as to quantify the degree of variability in this effect size across studies. Looking across 55 studies, we find that deviations from moderate temperatures and precipitation patterns systematically increase the risk of conflict, often substantially, with average effects that are highly statistically significant. We find that contemporaneous temperature has the largest average effect by far, with each 1σ increase toward warmer temperatures increasing the frequency of contemporaneous interpersonal conflict by 2.4% and of intergroup conflict by 11.3%, but that the 2-period cumulative effect of rainfall on intergroup conflict is also substantial (3.5%/σ). We also quantify heterogeneity in these effect estimates across settings that is likely important. We conclude by highlighting remaining challenges in this field and the approaches we expect will be most effective at solving them, including identifying mechanisms that link climate to conflict, measuring the ability of societies to adapt to climate changes, and understanding the likely impacts of future global warming.
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Leveraging scientific credibility about Arctic sea ice trends in a polarized political environment
Kathleen Hall Jamieson & Bruce Hardy
Proceedings of the National Academy of Sciences, 16 September 2014, Pages 13598-13605
Abstract:
This work argues that, in a polarized environment, scientists can minimize the likelihood that the audience’s biased processing will lead to rejection of their message if they not only eschew advocacy but also convey that they are sharers of knowledge faithful to science’s way of knowing and respectful of the audience’s intelligence; the sources on which they rely are well-regarded by both conservatives and liberals; and the message explains how the scientist arrived at the offered conclusion, is conveyed in a visual form that involves the audience in drawing its own conclusions, and capsulizes key inferences in an illustrative analogy. A pilot experiment raises the possibility that such a leveraging–involving–visualizing–analogizing message structure can increase acceptance of the scientific claims about the downward cross-decade trend in Arctic sea ice extent and elicit inferences consistent with the scientific consensus on climate change among conservatives exposed to misleadingly selective data in a partisan news source.
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Jeremiah Bohr
Climatic Change, September 2014, Pages 217-227
Abstract:
Previous research has identified the interaction between political orientation and education as an important predictor of climate change beliefs. Using data from the 2010 General Social Survey, this article looks at the moderating effect of party identification on income in predicting climate change beliefs in the U.S. Probing this interaction reveals that increased income predicts a higher probability of dismissing climate dangers among Republican-leaning individuals when compared with Independents and Democrats. Alternatively, increased income predicts a higher probability of ranking climate change as the most important environmental problem facing the United States among Democratic-leaning individuals compared with Republicans. The results indicate that income only predicts climate change beliefs in the presence of certain political orientations, with poorer Republicans less likely to dismiss climate change dangers than their affluent counterparts.
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Upper limit for sea level projections by 2100
S. Jevrejeva, A. Grinsted & J.C. Moore
Environmental Research Letters, October 2014
Abstract:
We construct the probability density function of global sea level at 2100, estimating that sea level rises larger than 180 cm are less than 5% probable. An upper limit for global sea level rise of 190 cm is assembled by summing the highest estimates of individual sea level rise components simulated by process based models with the RCP8.5 scenario. The agreement between the methods may suggest more confidence than is warranted since large uncertainties remain due to the lack of scenario-dependent projections from ice sheet dynamical models, particularly for mass loss from marine-based fast flowing outlet glaciers in Antarctica. This leads to an intrinsically hard to quantify fat tail in the probability distribution for global mean sea level rise. Thus our low probability upper limit of sea level projections cannot be considered definitive. Nevertheless, our upper limit of 180 cm for sea level rise by 2100 is based on both expert opinion and process studies and hence indicates that other lines of evidence are needed to justify a larger sea level rise this century.
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Estimating the Normal Background Rate of Species Extinction
Jurriaan De Vos et al.
Conservation Biology, forthcoming
Abstract:
A key measure of humanity's global impact is by how much it has increased species extinction rates. Familiar statements are that these are 100–1000 times pre-human or background extinction levels. Estimating recent rates is straightforward, but establishing a background rate for comparison is not. Previous researchers chose an approximate benchmark of 1 extinction per million species per year (E/MSY). We explored disparate lines of evidence that suggest a substantially lower estimate. Fossil data yield direct estimates of extinction rates, but they are temporally coarse, mostly limited to marine hard-bodied taxa, and generally involve genera not species. Based on these data, typical background loss is 0.01 genera per million genera per year. Molecular phylogenies are available for more taxa and ecosystems, but it is debated whether they can be used to estimate separately speciation and extinction rates. We selected data to address known concerns and used them to determine median extinction estimates from statistical distributions of probable values for terrestrial plants and animals. We then created simulations to explore effects of violating model assumptions. Finally, we compiled estimates of diversification — the difference between speciation and extinction rates for different taxa. Median estimates of extinction rates ranged from 0.023 to 0.135 E/MSY. Simulation results suggested over- and under-estimation of extinction from individual phylogenies partially canceled each other out when large sets of phylogenies were analyzed. There was no evidence for recent and widespread pre-human overall declines in diversity. This implies that average extinction rates are less than average diversification rates. Median diversification rates were 0.05–0.2 new species per million species per year. On the basis of these results, we concluded that typical rates of background extinction may be closer to 0.1 E/MSY. Thus, current extinction rates are 1,000 times higher than natural background rates of extinction and future rates are likely to be 10,000 times higher.
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Increased variability of tornado occurrence in the United States
Harold Brooks, Gregory Carbin & Patrick Marsh
Science, 17 October 2014, Pages 349-352
Abstract:
Whether or not climate change has had an impact on the occurrence of tornadoes in the United States has become a question of high public and scientific interest, but changes in how tornadoes are reported have made it difficult to answer it convincingly. We show that, excluding the weakest tornadoes, the mean annual number of tornadoes has remained relatively constant, but their variability of occurrence has increased since the 1970s. This is due to a decrease in the number of days per year with tornadoes combined with an increase in days with many tornadoes, leading to greater variability on annual and monthly time scales and changes in the timing of the start of the tornado season.
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Limited impact on decadal-scale climate change from increased use of natural gas
Haewon McJeon et al.
Nature, forthcoming
Abstract:
The most important energy development of the past decade has been the wide deployment of hydraulic fracturing technologies that enable the production of previously uneconomic shale gas resources in North America. If these advanced gas production technologies were to be deployed globally, the energy market could see a large influx of economically competitive unconventional gas resources. The climate implications of such abundant natural gas have been hotly debated. Some researchers have observed that abundant natural gas substituting for coal could reduce carbon dioxide (CO2) emissions. Others have reported that the non-CO2 greenhouse gas emissions associated with shale gas production make its lifecycle emissions higher than those of coal. Assessment of the full impact of abundant gas on climate change requires an integrated approach to the global energy–economy–climate systems, but the literature has been limited in either its geographic scope or its coverage of greenhouse gases. Here we show that market-driven increases in global supplies of unconventional natural gas do not discernibly reduce the trajectory of greenhouse gas emissions or climate forcing. Our results, based on simulations from five state-of-the-art integrated assessment models of energy–economy–climate systems independently forced by an abundant gas scenario, project large additional natural gas consumption of up to +170 per cent by 2050. The impact on CO2 emissions, however, is found to be much smaller (from −2 per cent to +11 per cent), and a majority of the models reported a small increase in climate forcing (from −0.3 per cent to +7 per cent) associated with the increased use of abundant gas. Our results show that although market penetration of globally abundant gas may substantially change the future energy system, it is not necessarily an effective substitute for climate change mitigation policy.
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Oliver Schneising et al.
Earth's Future, forthcoming
Abstract:
In the past decade there has been a massive growth in the horizontal drilling and hydraulic fracturing of shale gas and tight oil reservoirs to exploit formerly inaccessible or unprofitable energy resources in rock formations with low permeability. In North America, these unconventional domestic sources of natural gas and oil provide an opportunity to achieve energy self-sufficiency and to reduce greenhouse gas emissions when displacing coal as a source of energy in power plants. However, fugitive methane emissions in the production process may counter the benefit over coal with respect to climate change and therefore need to be well quantified. Here we demonstrate that positive methane anomalies associated with the oil and gas industries can be detected from space and that corresponding regional emissions can be constrained using satellite observations. Based on a mass-balance approach, we estimate that methane emissions for two of the fastest growing production regions in the United States, the Bakken and Eagle Ford formations, have increased by 990 ± 650 ktCH 4 yr − 1 and 530 ± 330 ktCH 4 yr − 1 between the periods 2006–2008 and 2009–2011. Relative to the respective increases in oil and gas production, these emission estimates correspond to leakages of 10.1 ± 7.3 % and 9.1 ± 6.2 % in terms of energy content, calling immediate climate benefit into question and indicating that current inventories likely underestimate fugitive emissions from Bakken and Eagle Ford.
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Local warming and violent conflict in North and South Sudan
Jean-François Maystadt, Margherita Calderone & Liangzhi You
Journal of Economic Geography, forthcoming
Abstract:
Our article contributes to the emerging micro-level strand of the literature on the link between local variations in weather shocks and conflicts by focusing on a pixel-level analysis for North and South Sudan between 1997 and 2009. Temperature anomalies are found to strongly affect the risk of conflict, whereas the risk is expected to magnify in a range of 24–31% in the future under a median scenario. Our analysis also sheds light on the competition over natural resources, in particular water, as the main driver of such relationship in a region where pastoralism constitutes the dominant livelihood.
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A Century of Ocean Warming on Florida Keys Coral Reefs: Historic In Situ Observations
Ilsa Kuffner et al.
Estuaries and Coasts, forthcoming
Abstract:
There is strong evidence that global climate change over the last several decades has caused shifts in species distributions, species extinctions, and alterations in the functioning of ecosystems. However, because of high variability on short (i.e., diurnal, seasonal, and annual) timescales as well as the recency of a comprehensive instrumental record, it is difficult to detect or provide evidence for long-term, site-specific trends in ocean temperature. Here we analyze five in situ datasets from Florida Keys coral reef habitats, including historic measurements taken by lighthouse keepers, to provide three independent lines of evidence supporting approximately 0.8 °C of warming in sea surface temperature (SST) over the last century. Results indicate that the warming observed in the records between 1878 and 2012 can be fully accounted for by the warming observed in recent decades (from 1975 to 2007), documented using in situ thermographs on a mid-shore patch reef. The magnitude of warming revealed here is similar to that found in other SST datasets from the region and to that observed in global mean surface temperature. The geologic context and significance of recent ocean warming to coral growth and population dynamics are discussed, as is the future prognosis for the Florida reef tract.
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The future of global water stress: An integrated assessment
Adam Schlosser et al.
Earth's Future, August 2014, Pages 341–361
Abstract:
We assess the ability of global water systems, resolved at 282 assessment subregions (ASRs), to the meet water requirements under integrated projections of socioeconomic growth and climate change. We employ a water resource system (WRS) component embedded within the Massachusetts Institute of Technology Integrated Global System Model (IGSM) framework in a suite of simulations that consider a range of climate policies and regional hydroclimate changes out to 2050. For many developing nations, water demand increases due to population growth and economic activity have a much stronger effect on water stress than climate change. By 2050, economic growth and population change alone can lead to an additional 1.8 billion people living under at least moderate water stress, with 80% of these located in developing countries. Uncertain regional climate change can play a secondary role to either exacerbate or dampen the increase in water stress. The strongest climate impacts on water stress are observed in Africa, but strong impacts also occur over Europe, Southeast Asia, and North America. The combined effects of socioeconomic growth and uncertain climate change lead to a 1.0–1.3 billion increase of the world's 2050 projected population living with overly exploited water conditions — where total potential water requirements will consistently exceed surface water supply. This would imply that adaptive measures would be taken to meet these surface water shortfalls and include: water-use efficiency, reduced and/or redirected consumption, recurrent periods of water emergencies or curtailments, groundwater depletion, additional interbasin transfers, and overdraw from flow intended to maintain environmental requirements.
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Why are climate policies of the present decade so crucial for keeping the 2 °C target credible?
Baptiste Perrissin Fabert et al.
Climatic Change, October 2014, Pages 337-349
Abstract:
Decision-makers have confirmed the long term objective of preventing a temperature increase greater than 2 °C. This paper aims at appraising by means of a cost-benefit analysis whether decision makers’ commitment to meet the 2 °C objective is credible or not. Within the framework of a cost-benefit type integrated assessment model, we consider that the economy faces climate damages with a threshold at 2 °C. We run the model for a broad set of scenarios accounting for the diversity of “worldviews” in the climate debate. For a significant share of scenarios we observe that it is considered optimal to exceed the threshold. Among those “non-compliers” we discriminate ”involuntary non-compliers” who cannot avoid the exceedance due to physical constraint from ”deliberate compliers” for whom the exceedance results from a deliberate costs-benefit analysis. A second result is that the later mitigation efforts begin, the more difficult it becomes to prevent the exceedance. In particular, the number of ”deliberate non-compliers” dramatically increases if mitigation efforts do not start by 2020, and the influx of involuntary non-compliers become overwhelming if efforts are delayed to 2040. In light of these results we argue that the window of opportunity for reaching the 2 °C objective with a credible chance of success is rapidly closing during the present decade. Further delay in finding a climate agreement critically undermines the credibility of the objective.
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Antarctic outlet glacier mass change resolved at basin scale from satellite gravity gradiometry
J. Bouman et al.
Geophysical Research Letters, 28 August 2014, Pages 5919–5926
Abstract:
The orbit and instrumental measurement of the Gravity Field and Steady State Ocean Circulation Explorer (GOCE) satellite mission offer the highest ever resolution capabilities for mapping Earth's gravity field from space. However, past analysis predicted that GOCE would not detect changes in ice sheet mass. Here we demonstrate that GOCE gravity gradiometry observations can be combined with Gravity Recovery and Climate Experiment (GRACE) gravity data to estimate mass changes in the Amundsen Sea Sector. This refined resolution allows land ice changes within the Pine Island Glacier (PIG), Thwaites Glacier, and Getz Ice Shelf drainage systems to be measured at respectively −67 ± 7, −63 ± 12, and −55 ± 9 Gt/yr over the GOCE observing period of November 2009 to June 2012. This is the most accurate pure satellite gravimetry measurement to date of current mass loss from PIG, known as the “weak underbelly” of West Antarctica because of its retrograde bed slope and high potential for raising future sea level.
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Distributional Implications of Climate Change in Rural India: A General Equilibrium Approach
Hanan Jacoby, Mariano Rabassa & Emmanuel Skoufias
American Journal of Agricultural Economics, forthcoming
Abstract:
We develop a general equilibrium framework, based on a specific-factors trade model, to quantify the medium-term household welfare impacts of global warming in rural India. Using an hedonic approach grounded in the theory combined with detailed microdata, we estimate that three decades of warming will reduce agricultural productivity in the range of 7%–13%, with the arid northwest of India especially hard hit. Our analysis shows that the proportional welfare cost of climate change is likely to be both modest and evenly distributed across percentiles of the per capita income distribution, but this latter conclusion emerges only when the flexibility of rural wages is taken into account.
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Life cycle environmental impacts of UK shale gas
Laurence Stamford & Adisa Azapagic
Applied Energy, 1 December 2014, Pages 506–518
Abstract:
Exploitation of shale gas in the UK is at a very early stage, but with the latest estimates suggesting potential resources of 3.8 × 1013 cubic metres – enough to supply the UK for next 470 years – it is viewed by many as an exciting economic prospect. However, its environmental impacts are currently unknown. This is the focus of this paper which estimates for the first time the life cycle impacts of UK shale gas, assuming its use for electricity generation. Shale gas is compared to fossil-fuel alternatives (conventional gas and coal) and low-carbon options (nuclear, offshore wind and solar photovoltaics). The results suggest that the impacts range widely, depending on the assumptions. For example, the global warming potential (GWP100) of electricity from shale gas ranges from 412 to 1102 g CO2-eq./kWh with a central estimate of 462 g. The central estimates suggest that shale gas is comparable or superior to conventional gas and low-carbon technologies for depletion of abiotic resources, eutrophication, and freshwater, marine and human toxicities. Conversely, it has a higher potential for creation of photochemical oxidants (smog) and terrestrial toxicity than any other option considered. For acidification, shale gas is a better option than coal power but an order of magnitude worse than the other options. The impact on ozone layer depletion is within the range found for conventional gas, but nuclear and wind power are better options still. The results of this research highlight the need for tight regulation and further analysis once typical UK values of key parameters for shale gas are established, including its composition, recovery per well, fugitive emissions and disposal of drilling waste.
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Estimating climate change effects on net primary production of rangelands in the United States
Matthew Reeves et al.
Climatic Change, October 2014, Pages 429-442
Abstract:
The potential effects of climate change on net primary productivity (NPP) of U.S. rangelands were evaluated using estimated climate regimes from the A1B, A2 and B2 global change scenarios imposed on the biogeochemical cycling model, Biome-BGC from 2001 to 2100. Temperature, precipitation, vapor pressure deficit, day length, solar radiation, CO2 enrichment and nitrogen deposition were evaluated as drivers of NPP. Across all three scenarios, rangeland NPP increased by 0.26 % year−1 (7 kg C ha−1 year−1) but increases were not apparent until after 2030 and significant regional variation in NPP was revealed. The Desert Southwest and Southwest assessment regions exhibited declines in NPP of about 7 % by 2100, while the Northern and Southern Great Plains, Interior West and Eastern Prairies all experienced increases over 25 %. Grasslands dominated by warm season (C4 photosynthetic pathway) species showed the greatest response to temperature while cool season (C3 photosynthetic pathway) dominated regions responded most strongly to CO2 enrichment. Modeled NPP responses compared favorably with experimental results from CO2 manipulation experiments and to NPP estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS). Collectively, these results indicate significant and asymmetric changes in NPP for U.S. rangelands may be expected.
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Discounting the Distant Future: An Experimental Investigation
Therese Grijalva, Jayson Lusk & Douglass Shaw
Environmental and Resource Economics, September 2014, Pages 39-63
Abstract:
We use a laboratory experiment to elicit discount rates over a 20-year time horizon using government savings bonds as a payment vehicle. When using a constant (exponential) discount rate function, we find an implied average discount rate of 4.9 %, which is much lower than has been found in previous experimental studies that used time horizons of days or months. However, we also find strong support for non-constant, declining discount rates for longer time horizons, with an extrapolated implied annual discount rate approaching 0.5 % in 100 years. There is heterogeneity in discount rates and risk preferences in that people with more optimistic beliefs about technological progress have higher discount rates. These findings contribute to the debate over the appropriate discount rate to use in comparing the long-term benefits of climate change mitigation to the more immediate costs.