Cloudy with a chance of...
Temperature Shocks and Economic Growth: Evidence from the Last Half Century
Melissa Dell, Benjamin Jones & Benjamin Olken
American Economic Journal: Macroeconomics, forthcoming
Abstract:
This paper uses historical fluctuations in temperature within countries to identify its effects on aggregate economic outcomes. We find three primary results. First, higher temperatures substantially reduce economic growth in poor countries. Second, higher temperatures appear to reduce growth rates, not just the level of output. Third, higher temperatures have wide-ranging effects, reducing agricultural output, industrial output, and political stability. These findings inform debates over climate's role in economic development and suggest the possibility of substantial negative impacts of higher temperatures on poor countries.
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Buy Coal! A Case for Supply-Side Environmental Policy
Bård Harstad
Journal of Political Economy, February 2012, Pages 77-115
Abstract:
Free-riding is at the core of environmental problems. If a climate coalition reduces its emissions, world prices change and nonparticipants typically emit more; they may also extract the dirtiest type of fossil fuel and invest too little in green technology. The coalition's second-best policy distorts trade and is not time consistent. However, suppose that the countries can trade the rights to exploit fossil-fuel deposits: As soon as the market clears, the above-mentioned problems vanish and the first-best is implemented. In short, the coalition's best policy is to simply buy foreign deposits and conserve them.
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Economic Policy in the Face of Severe Tail Events
William Nordhaus
Journal of Public Economic Theory, March 2012, Pages 197-219
Abstract:
From time to time, something occurs which is outside the range of normal expectations. We will call these "tail events" in the sense that they are way out of the tail of a probability distribution. I consider the question of the implications of tail events for economic policy and climate-change economics. This issue has been analyzed by Martin Weitzman who proposed a Dismal Theorem. The general idea is that, under limited conditions concerning the structure of uncertainty and risk aversion, society has an indefinitely large expected loss from high-consequence, low-probability events. Under such conditions, standard economic tools such as cost-benefit analysis cannot be applied. The present study is intended to put the Dismal Theorem in context and examine the range of its relevance, with an application to catastrophic climate change. I conclude that tail events are sometimes of extreme importance, and we must be extremely careful to include them in situations of deep uncertainty. However, we conclude that no loaded gun of strong tail dominance has been uncovered to date.
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Women's Status and Carbon Dioxide Emissions: A Quantitative Cross-National Analysis
Christina Ergas & Richard York
Social Science Research, forthcoming
Abstract:
Global climate change is one of the most severe problems facing societies around the world. Very few assessments of the social forces that influence greenhouse gas emissions have examined gender inequality. Empirical research suggests that women are more likely than men to support environmental protection. Various strands of feminist theory suggest that this is due to women's traditional roles as caregivers, subsistence food producers, water and fuelwood collectors, and reproducers of human life. Other theorists argue that women's status and environmental protection are linked because the exploitation of women and the exploitation of nature are interconnected processes. For these theoretical and empirical reasons, we hypothesize that in societies with greater gender equality there will be relatively lower impacts on the environment, controlling for other factors. We test this hypothesis using quantitative analysis of cross-national data, focusing on the connection between women's political status and CO2 emissions per capita. We find that CO2 emissions per capita are lower in nations where women have higher political status, controlling for GDP per capita, urbanization, industrialization, militarization, world-system position, foreign direct investment, the age dependency ratio, and level of democracy. This finding suggests that efforts to improve gender equality around the world may work synergistically with efforts to curtail global climate change and environmental degradation more generally.
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135 years of global ocean warming between the Challenger expedition and the Argo Programme
Dean Roemmich, John Gould & John Gilson
Nature Climate Change, forthcoming
Abstract:
Changing temperature throughout the oceans is a key indicator of climate change. Since the 1960s about 90% of the excess heat added to the Earth's climate system has been stored in the oceans. The ocean's dominant role over the atmosphere, land, or cryosphere comes from its high heat capacity and ability to remove heat from the sea surface by currents and mixing. The longest interval over which instrumental records of subsurface global-scale temperature can be compared is the 135 years between the voyage of HMS Challenger (1872-1876) and the modern data set of the Argo Programme (2004-2010). Argo's unprecedented global coverage permits its comparison with any earlier measurements. This, the first global-scale comparison of Challenger and modern data, shows spatial mean warming at the surface of 0.59 °C±0.12, consistent with previous estimates of globally averaged sea surface temperature increase. Below the surface the mean warming decreases to 0.39 °C±0.18 at 366 m (200 fathoms) and 0.12 °C±0.07 at 914 m (500 fathoms). The 0.33 °C±0.14 average temperature difference from 0 to 700 m is twice the value observed globally in that depth range over the past 50 years, implying a centennial timescale for the present rate of global warming. Warming in the Atlantic Ocean is stronger than in the Pacific. Systematic errors in the Challenger data mean that these temperature changes are a lower bound on the actual values. This study underlines the scientific significance of the Challenger expedition and the modern Argo Programme and indicates that globally the oceans have been warming at least since the late-nineteenth or early-twentieth century.
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In the Wake of the Spill: Environmental Views Along the Gulf Coast
Lawrence Hamilton, Thomas Safford & Jessica Ulrich
Social Science Quarterly, forthcoming
Objectives: We analyze patterns in environmental views of Gulf Coast residents, in the wake of the 2010 oil spill. To what extent do spill-related and other environmental views vary with individual characteristics, personal experience with the spill, or characteristics of place?
Methods: About 2,000 residents of selected coastal regions in Louisiana and Florida were interviewed by telephone in late summer 2010.
Results: One-quarter of the respondents said that their environmental views had changed as a result of the spill. Despite reporting more change, more spill effects, and greater threats from climate-induced sea-level rise, Louisiana respondents were less likely to support a deepwater moratorium, alternative energy, or resource conservation.
Conclusions: Results are consistent with real effects from the spill. Differences between Louisiana and Florida respondents are not explained by spill effects or individual characteristics, however. The patterns reflect biophysical differences of the coastlines that shaped their socioeconomic development.
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Insights from past millennia into climatic impacts on human health and survival
Anthony McMichael
Proceedings of the National Academy of Sciences, 27 March 2012, Pages 4730-4737
Abstract:
Climate change poses threats to human health, safety, and survival via weather extremes and climatic impacts on food yields, fresh water, infectious diseases, conflict, and displacement. Paradoxically, these risks to health are neither widely nor fully recognized. Historical experiences of diverse societies experiencing climatic changes, spanning multicentury to single-year duration, provide insights into population health vulnerability - even though most climatic changes were considerably less than those anticipated this century and beyond. Historical experience indicates the following. (i) Long-term climate changes have often destabilized civilizations, typically via food shortages, consequent hunger, disease, and unrest. (ii) Medium-term climatic adversity has frequently caused similar health, social, and sometimes political consequences. (iii) Infectious disease epidemics have often occurred in association with briefer episodes of temperature shifts, food shortages, impoverishment, and social disruption. (iv) Societies have often learnt to cope (despite hardship for some groups) with recurring shorter-term (decadal to multiyear) regional climatic cycles (e.g., El Niño Southern Oscillation) - except when extreme phases occur. (v) The drought-famine-starvation nexus has been the main, recurring, serious threat to health. Warming this century is not only likely to greatly exceed the Holocene's natural multidecadal temperature fluctuations but to occur faster. Along with greater climatic variability, models project an increased geographic range and severity of droughts. Modern societies, although larger, better resourced, and more interconnected than past societies, are less flexible, more infrastructure-dependent, densely populated, and hence are vulnerable. Adverse historical climate-related health experiences underscore the case for abating human-induced climate change.
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J.T. Smith, N.J. Willey & J.T. Hancock
Biology Letters, forthcoming
Abstract:
It has been hypothesized that radiation-induced oxidative stress is the mechanism for a wide range of negative impacts on biota living in radioactively contaminated areas around Chernobyl. The present study tests this hypothesis mechanistically, for the first time, by modelling the impacts of radiolysis products within the cell resulting from radiations (low linear energy transfer β and γ), and dose rates appropriate to current contamination types and densities in the Chernobyl exclusion zone and at Fukushima. At 417 µGy h-1 (illustrative of the most contaminated areas at Chernobyl), generation of radiolysis products did not significantly impact cellular concentrations of reactive oxygen species, or cellular redox potential. This study does not support the hypothesis that direct oxidizing stress is a mechanism for damage to organisms exposed to chronic radiation at dose rates typical of contaminated environments.
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On the inverse relationship between North American snow extent and North Atlantic hurricane activity
T. Yan et al.
International Journal of Climatology, forthcoming
Abstract:
The statistically significant inverse relationship is examined between North American snow cover extent during January and North Atlantic hurricane activity during the following hurricane season. To better quantify this relationship the long-term trend and ENSO years were removed from the data. The lightest January snow-cover years (LSY) show sharp increases (40-90%) compared to the heaviest January snow-cover years (HSY) in nearly all measures of Atlantic hurricane activity, including the numbers and duration of hurricanes and major hurricanes, and the average seasonal accumulated cyclone energy (ACE) index. Approximately, half of the LSY events featured above-normal hurricane seasons and none were below-normal, while approximately half of the HSY featured below-normal hurricane seasons none were above-normal. Composite analyses indicate the anomalous wintertime snow-cover extent and Atlantic hurricane activity are linked through their common association with persistent and hemisphere-wide extratropical circulation anomalies tied to the Arctic Oscillation (AO). The LSY are associated with a positive phase of the AO, along with warmer surface temperatures in both North America and Eurasia, while the HSY are associated with a negative phase of the AO and below-average continental surface temperatures. One unresolved issue is the extent to which the anomalous snow extent feeds back onto the large-scale circulation so as to help maintain the wintertime AO patterns through the spring and summer. Another remaining issue is the process(es) by which the extratropical AO signals eventually penetrate into the tropics so as to influence Atlantic hurricane activity.
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Richard Hornbeck
American Economic Review, forthcoming
Abstract:
The 1930's American Dust Bowl was an environmental catastrophe that greatly eroded sections of the Plains. The Dust Bowl is estimated to have immediately, substantially, and persistently reduced agricultural land values and revenues in more-eroded counties relative to less-eroded counties. During the Depression and through at least the 1950's, there was limited relative adjustment of farmland away from activities that became relatively less productive in more-eroded areas. Agricultural adjustments recovered less than 25% of the initial difference in agricultural costs for more-eroded counties. The economy adjusted predominately through large relative population declines in more-eroded counties, both during the 1930's and through the 1950's.
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Industry Influence in Stakeholder-Driven State Climate Change Planning Efforts
Elena Maggioni, Hal Nelson & Daniel Mazmanian
Policy Studies Journal, May 2012, Pages 234-255
Abstract:
Drawing from the literature on public participation and stakeholder collaboratives, this article investigates the influence of power and wealth, as well as political and economic context on the output of stakeholders advisory committees convened to formulate state greenhouse gas (GHG) mitigation policies. Using small sample regression techniques, we analyze the outputs of stakeholder groups in 18 states that have completed Climate Action Plans to reduce GHGs. We find that an increase of 1 percent in the number of energy industry representatives that participate in Climate Action Councils significantly predicts a 4 percent reduction of GHG mitigation targets for the energy sector. More surprisingly, the results also show that where the utilities represent a larger share of the state economy, the Climate Action Plans identify more aggressive GHG reduction goals for the energy sector. We also find that the political orientation of the executive of the state is not correlated with GHG mitigation requirements for the energy sector, suggesting that GHG mitigation is less partisan at the state level than in Washington, DC. We find no evidence that state wealth is associated with GHG mitigation requirements. Finally, we suggest additional research needed to clarify the role of stakeholder participation processes in the evolving arena of climate change policy.
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Nicholas Smith & Anthony Leiserowitz
Risk Analysis, forthcoming
Abstract:
This article explores how affective image associations to global warming have changed over time. Four nationally representative surveys of the American public were conducted between 2002 and 2010 to assess public global warming risk perceptions, policy preferences, and behavior. Affective images (positive or negative feelings and cognitive representations) were collected and content analyzed. The results demonstrate a large increase in "naysayer" associations, indicating extreme skepticism about the issue of climate change. Multiple regression analyses found that holistic affect and "naysayer" associations were more significant predictors of global warming risk perceptions than cultural worldviews or sociodemographic variables, including political party and ideology. The results demonstrate the important role affective imagery plays in judgment and decision-making processes, how these variables change over time, and how global warming is currently perceived by the American public.
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Climate change and moral judgement
Ezra Markowitz & Azim Shariff
Nature Climate Change, April 2012, Pages 243-247
Abstract:
Converging evidence from the behavioural and brain sciences suggests that the human moral judgement system is not well equipped to identify climate change - a complex, large-scale and unintentionally caused phenomenon - as an important moral imperative. As climate change fails to generate strong moral intuitions, it does not motivate an urgent need for action in the way that other moral imperatives do. We review six reasons why climate change poses significant challenges to our moral judgement system and describe six strategies that communicators might use to confront these challenges. Enhancing moral intuitions about climate change may motivate greater support for ameliorative actions and policies.
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Joëlle Noailly
Energy Economics, May 2012, Pages 795-806
Abstract:
This paper investigates the impact of alternative environmental policy instruments on technological innovations aiming to improve energy efficiency in buildings. The empirical analysis focuses on three main types of policy instruments, namely regulatory energy standards in buildings codes, energy taxes as captured by energy prices and specific governmental energy R&D expenditures. Technological innovation is measured using patent counts for specific technologies related to energy efficiency in buildings (e.g. insulation, high-efficiency boilers, energy-saving lightings). The estimates for seven European countries over the 1989-2004 period imply that a strengthening of 10% of the minimum insulation standards for walls would increase the likelihood to file additional patents by about 3%. In contrast, energy prices have no significant effect on the likelihood to patent. Governmental energy R&D support has a small positive significant effect on patenting activities.
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Economic impacts of climate change in Europe: Sea-level rise
Francesco Bosello et al.
Climatic Change, May 2012, Pages 63-81
Abstract:
This paper uses two models to examine the direct and indirect costs of sea-level rise for Europe for a range of sea-level rise scenarios for the 2020s and 2080s: (1) the DIVA model to estimate the physical impacts of sea-level rise and the direct economic cost, including adaptation, and (2) the GTAP-EF model to assess the indirect economic implications. Without adaptation, impacts are quite significant with a large land loss and increase in the incidence of coastal flooding. By the end of the century Malta has the largest relative land loss at 12% of its total surface area, followed by Greece at 3.5% land loss. Economic losses are however larger in Poland and Germany (483 and391 million, respectively). Coastal protection is very effective in reducing these impacts and optimally undertaken leads to protection levels that are higher than 85% in the majority of European states. While the direct economic impact of sea-level rise is always negative, the final impact on countries' economic performances estimated with the GTAP-EF model may be positive or negative. This is because factor substitution, international trade, and changes in investment patterns interact with possible positive implications. The policy insights are (1) while sea-level rise has negative and huge direct economic effects, overall effects on GDP are quite small (max -0.046% in Poland); (2) the impact of sea-level rise is not confined to the coastal zone and sea-level rise indirectly affects landlocked countries as well (Austria for instance loses -0.003% of its GDP); and (3) adaptation is crucial to keep the negative impacts of sea-level rise at an acceptable level.
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Greater focus needed on methane leakage from natural gas infrastructure
Ramón Alvarez et al.
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
Natural gas is seen by many as the future of American energy: a fuel that can provide energy independence and reduce greenhouse gas emissions in the process. However, there has also been confusion about the climate implications of increased use of natural gas for electric power and transportation. We propose and illustrate the use of technology warming potentials as a robust and transparent way to compare the cumulative radiative forcing created by alternative technologies fueled by natural gas and oil or coal by using the best available estimates of greenhouse gas emissions from each fuel cycle (i.e., production, transportation and use). We find that a shift to compressed natural gas vehicles from gasoline or diesel vehicles leads to greater radiative forcing of the climate for 80 or 280 yr, respectively, before beginning to produce benefits. Compressed natural gas vehicles could produce climate benefits on all time frames if the well-to-wheels CH4 leakage were capped at a level 45-70% below current estimates. By contrast, using natural gas instead of coal for electric power plants can reduce radiative forcing immediately, and reducing CH4 losses from the production and transportation of natural gas would produce even greater benefits. There is a need for the natural gas industry and science community to help obtain better emissions data and for increased efforts to reduce methane leakage in order to minimize the climate footprint of natural gas.
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Rational habits in gasoline demand
Rebecca Scott
Energy Economics, forthcoming
Abstract:
The dynamics of demand for energy goods such as gasoline are complicated by investment decisions and behavioral habits. Both types of complication can be captured by a habits model, in which past consumption enters into an agent's current utility function. If the agent is forward-looking, or ‘rational', then habits imply his consumption of the habit-forming good will be sensitive to his expectation of future market conditions, in particular future prices. This sensitivity implies, in turn, that traditional measures of price elasticity will underproject consumers' responsiveness to policy interventions. This paper examines the implications of rational habits on gasoline demand. Using a simple model encompassing myopic and rational habits, I demonstrate that an agent with rational habits will respond to anticipated future price changes and react more strongly to permanent than to temporary price changes, with this distinction increasing in the strength of the habit. I then estimate several habits models using panel data on U.S. states for the years 1989 through 2008. My preferred specification yields evidence of rational habits, and moreover I find consumers to be twice as responsive to tax-driven price changes as to market-driven price changes. Taxes and other policies that operate through the gasoline price are a more powerful policy instrument than traditional price elasticity would lead us to believe.
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Gasoline Taxes and Consumer Behavior
Shanjun Li, Joshua Linn & Erich Muehlegger
NBER Working Paper, March 2012
Abstract:
Gasoline taxes can be employed to correct externalities associated with automobile use, to reduce dependency on foreign oil, and to raise government revenue. Our understanding of the optimal gasoline tax and the efficacy of existing taxes is largely based on empirical analysis of consumer responses to gasoline price changes. In this paper, we directly examine how gasoline taxes affect consumer behavior as distinct from tax-exclusive gasoline prices. Our analysis shows that a 5-cent tax increase reduces gasoline consumption by 1.3 percent in the short-run, much larger than that from a 5-cent increase in the tax-exclusive gasoline price. This difference suggests that traditional analysis could significantly underestimate policy impacts of tax changes. We further investigate the differential effect from gasoline taxes and tax-exclusive gasoline prices on both the intensive and extensive margins of gasoline consumption. We discuss implications of our findings for the estimation of the implicit discount rate for vehicle purchases and for the fiscal benefits of raising taxes.
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Is there a case for carbon-based border tax adjustment? An applied general equilibrium analysis
Jean-Marc Burniaux, Jean Chateau & Romain Duval
Applied Economics, Spring 2012, Pages 2231-2240
Abstract:
Concern that unilateral Greenhouse Gas (GHG) emission reductions could foster carbon leakage and undermine the international competitiveness of domestic industry has led to growing calls for carbon-based Border-Tax Adjustments (BTAs). This article uses a global general equilibrium model to assess the economic effects of BTAs and comes to three main conclusions. First, BTAs can reduce carbon leakage if the coalition of countries taking action to reduce GHG emissions is small, because in this case leakage (while typically small) mainly occurs through international trade competitiveness losses rather than through declines in world fossil fuel prices. Second, even though the economic effects of BTAs vary somewhat depending on how they are implemented, their welfare impact is typically small, and slightly negative at the world level. Third, and perhaps more strikingly, BTAs do not necessarily curb the output losses incurred by the domestic Energy Intensive-Industries (EIIs) they are intended to protect in the first place. This is in part because EIIs in industrialized countries make important use of carbon-intensive intermediate inputs produced by EIIs in other geographical areas. Another, deeper explanation is that EIIs are ultimately more adversely affected by the existence of a carbon price itself than by any international competitiveness losses. These findings are shown to be robust to key model parameters, country coverage, targets and design features of BTAs.
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Past extreme warming events linked to massive carbon release from thawing permafrost
Robert DeConto et al.
Nature, 5 April 2012, Pages 87-91
Abstract:
Between about 55.5 and 52 million years ago, Earth experienced a series of sudden and extreme global warming events (hyperthermals) superimposed on a long-term warming trend. The first and largest of these events, the Palaeocene-Eocene Thermal Maximum (PETM), is characterized by a massive input of carbon, ocean acidification and an increase in global temperature of about 5 °C within a few thousand years. Although various explanations for the PETM have been proposed, a satisfactory model that accounts for the source, magnitude and timing of carbon release at the PETM and successive hyperthermals remains elusive. Here we use a new astronomically calibrated cyclostratigraphic record from central Italy to show that the Early Eocene hyperthermals occurred during orbits with a combination of high eccentricity and high obliquity. Corresponding climate-ecosystem-soil simulations accounting for rising concentrations of background greenhouse gases and orbital forcing show that the magnitude and timing of the PETM and subsequent hyperthermals can be explained by the orbitally triggered decomposition of soil organic carbon in circum-Arctic and Antarctic terrestrial permafrost. This massive carbon reservoir had the potential to repeatedly release thousands of petagrams (1015 grams) of carbon to the atmosphere-ocean system, once a long-term warming threshold had been reached just before the PETM. Replenishment of permafrost soil carbon stocks following peak warming probably contributed to the rapid recovery from each event, while providing a sensitive carbon reservoir for the next hyperthermal. As background temperatures continued to rise following the PETM, the areal extent of permafrost steadily declined, resulting in an incrementally smaller available carbon pool and smaller hyperthermals at each successive orbital forcing maximum. A mechanism linking Earth's orbital properties with release of soil carbon from permafrost provides a unifying model accounting for the salient features of the hyperthermals.
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Optimal global carbon management with ocean sequestration
Wilfried Rickels & Thomas Lontzek
Oxford Economic Papers, April 2012, Pages 323-349
Abstract:
We investigate the socially optimal intervention in the global carbon cycle. Limiting factors are (i) increasing atmospheric carbon concentration due to fossil fuel-related carbon emissions, and (ii) the inertia of the global carbon cycle itself. Accordingly, we explicitly include the largest non-atmospheric carbon reservoir, the ocean, to achieve a better representation of the global carbon cycle than the proportional-decay assumption usually resorted to in economic models. We also investigate the option to directly inject CO2 into the deep ocean (a form of carbon sequestration), deriving from this a critical level for ocean sequestration costs. Above this level, ocean sequestration is merely a temporary option; below it, ocean sequestration is the long-term option permitting extended use of fossil fuels. The latter alternative involves higher atmospheric stabilization levels. In this connection it should be noted that the efficiency of ocean sequestration depends on the time-preference and the inertia of the carbon cycle.
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Shunsuke Mori
Energy Economics, forthcoming
Abstract:
This paper presents an evaluation of global warming mitigation options based on scenarios from the Asian Modeling Exercise. Using an extended version of the integrated assessment model MARIA-23 (Multiregional Approach for Resource and Industry Allocation), we analyze nuclear fuel recycling options, carbon capture and storage technologies (CCS), and biomass utilization. To assess the potential implications of decreased social acceptance of nuclear power in the wake of the Fukushima nuclear accident, additional scenarios including a nuclear power expansion limitation, are analyzed. We also evaluate MARIA-23 model simulation estimates of long-term contributions and interrelationships among nuclear power, biomass, and CCS. Finally, potential costs of nuclear limitation under carbon control policies are assessed. The simulation results in this paper suggest the following: (1) under the reference scenario, global GDP losses in climate limitation scenarios range from 1.3% per year to 3.9% per year in 2060, rising to between 3.5% per year and 4.5% per year in 2100; (2) the use of nuclear fuel reprocessing technologies increase rapidly in all carbon control policy scenarios; (3) under a scenario where the price of CO2 is $30 and nuclear power expansion is strictly limited, GDP losses increase significantly - from 4.5% per year to 6.4% per year by 2100; (4) nuclear power and CCS are substitute mitigation technologies. With nuclear power technology available CCS deployment reaches approximately 15,000Mt-CO2 per year by 2010; without a nuclear power option, CCS deployment rises to more than 80,000 Mt-CO2 per year; and (5) biomass utilization cannot fully compensate for limitations to nuclear power expansion in policy scenarios. In addition to examining the role of these three technologies on global scales, we report results for several major Asian regions, namely Japan, China, and India. China tends to deploy nuclear power (if available) in response to rapidly growing power demands, in all scenarios while India tends to rely less on nuclear power. The potential cost of nuclear power limitation under global warming mitigation in Japan is estimated be significantly higher than in China or India.
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Global trends in tropical cyclone risk
P. Peduzzi et al.
Nature Climate Change, April 2012, Pages 289-294
Abstract:
The impact of tropical cyclones on humans depends on the number of people exposed and their vulnerability, as well as the frequency and intensity of storms. How will the cumulative effects of climate change, demography and vulnerability affect risk? Conventionally, reports assessing tropical cyclone risk trends are based on reported losses, but these figures are biased by improvements to information access. Here we present a new methodology based on thousands of physically observed events and related contextual parameters. We show that mortality risk depends on tropical cyclone intensity, exposure, levels of poverty and governance. Despite the projected reduction in the frequency of tropical cyclones, projected increases in both demographic pressure and tropical cyclone intensity over the next 20 years can be expected to greatly increase the number of people exposed per year and exacerbate disaster risk, despite potential progression in development and governance.
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Externalities, Internalities, and the Targeting of Energy Policy
Hunt Allcott, Sendhil Mullainathan & Dmitry Taubinsky
NBER Working Paper, April 2012
Abstract:
We show how the traditional logic of Pigouvian externality taxes changes if consumers under-value energy costs when buying energy-using durables such as cars and air conditioners. First, with undervaluation, there is an "Internality Dividend" from externality taxes: aside from reducing the provision of public bads, they also reduce allocative inefficiencies caused by consumers' underinvestment in energy efficient durables. Second, although Pigouvian taxes are clearly the preferred policy mechanism when externalities are the only market failure, undervaluation provides an "Internality Rationale" for alternative policies such as product subsidies that reduce the relative price of energy efficient durables. However, when some consumers misoptimize and others do not, a crucial quantity for policy analysis is the average marginal internality: the extent to which a policy preferentially targets misoptimizing consumers. As an example of the importance of the average marginal internality, we carry out a randomized field experiment to provide rebates for energy efficient lightbulbs and illustrate how the welfare effects of the rebate depend significantly on whether consumers that undervalue energy costs are more or less elastic.
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Analysis of Arctic and Antarctic sea ice extent using quantile regression
Reza Tareghian & Peter Rasmussen
International Journal of Climatology, forthcoming
Abstract:
A number of recent studies have examined trends in sea ice cover using ordinary least squares regression. In this study, quantile regression is applied to analyse other aspects of the distribution of sea ice extent. More specifically, trends in the mean, maximum, and minimum sea ice extent in the Arctic and Antarctic are investigated. While there is a significant decreasing trend in mean Arctic sea ice extent of - 4.5% per decade from 1979 through 2010, the Antarctic results show a small positive trend of 2.3% per decade. In some cases such as the Antarctic minimum ice cover, selected quantile regressions yield slope estimates that differ from trends in the mean. It was also found that the variability in Antarctic sea ice extent is higher than that in the Arctic.
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Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability
Ben Booth et al.
Nature, forthcoming
Abstract:
Systematic climate shifts have been linked to multidecadal variability in observed sea surface temperatures in the North Atlantic Ocean. These links are extensive, influencing a range of climate processes such as hurricane activity and African Sahel and Amazonian droughts. The variability is distinct from historical global-mean temperature changes and is commonly attributed to natural ocean oscillations. A number of studies have provided evidence that aerosols can influence long-term changes in sea surface temperatures, but climate models have so far failed to reproduce these interactions and the role of aerosols in decadal variability remains unclear. Here we use a state-of-the-art Earth system climate model to show that aerosol emissions and periods of volcanic activity explain 76 per cent of the simulated multidecadal variance in detrended 1860-2005 North Atlantic sea surface temperatures. After 1950, simulated variability is within observational estimates; our estimates for 1910-1940 capture twice the warming of previous generation models but do not explain the entire observed trend. Other processes, such as ocean circulation, may also have contributed to variability in the early twentieth century. Mechanistically, we find that inclusion of aerosol-cloud microphysical effects, which were included in few previous multimodel ensembles, dominates the magnitude (80 per cent) and the spatial pattern of the total surface aerosol forcing in the North Atlantic. Our findings suggest that anthropogenic aerosol emissions influenced a range of societally important historical climate events such as peaks in hurricane activity and Sahel drought. Decadal-scale model predictions of regional Atlantic climate will probably be improved by incorporating aerosol-cloud microphysical interactions and estimates of future concentrations of aerosols, emissions of which are directly addressable by policy actions.
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Historical Temperature Variability Affects Coral Response to Heat Stress
Jessica Carilli, Simon Donner & Aaron Hartmann
PLoS ONE, March 2012
Abstract:
Coral bleaching is the breakdown of symbiosis between coral animal hosts and their dinoflagellate algae symbionts in response to environmental stress. On large spatial scales, heat stress is the most common factor causing bleaching, which is predicted to increase in frequency and severity as the climate warms. There is evidence that the temperature threshold at which bleaching occurs varies with local environmental conditions and background climate conditions. We investigated the influence of past temperature variability on coral susceptibility to bleaching, using the natural gradient in peak temperature variability in the Gilbert Islands, Republic of Kiribati. The spatial pattern in skeletal growth rates and partial mortality scars found in massive Porites sp. across the central and northern islands suggests that corals subject to larger year-to-year fluctuations in maximum ocean temperature were more resistant to a 2004 warm-water event. In addition, a subsequent 2009 warm event had a disproportionately larger impact on those corals from the island with lower historical heat stress, as indicated by lower concentrations of triacylglycerol, a lipid utilized for energy, as well as thinner tissue in those corals. This study indicates that coral reefs in locations with more frequent warm events may be more resilient to future warming, and protection measures may be more effective in these regions.
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Keith Smith et al.
Philosophical Transactions of the Royal Society: Biological Sciences, 5 May 2012, Pages 1169-1174
Abstract:
In earlier work, we compared the amount of newly fixed nitrogen (N, as synthetic fertilizer and biologically fixed N) entering agricultural systems globally to the total emission of nitrous oxide (N2O). We obtained an N2O emission factor (EF) of 3-5%, and applied it to biofuel production. For ‘first-generation' biofuels, e.g. biodiesel from rapeseed and bioethanol from corn (maize), that require N fertilizer, N2O from biofuel production could cause (depending on N uptake efficiency) as much or more global warming as that avoided by replacement of fossil fuel by the biofuel. Our subsequent calculations in a follow-up paper, using published life cycle analysis (LCA) models, led to broadly similar conclusions. The N2O EF applies to agricultural crops in general, not just to biofuel crops, and has made possible a top-down estimate of global emissions from agriculture. Independent modelling by another group using bottom-up IPCC inventory methodology has shown good agreement at the global scale with our top-down estimate. Work by Davidson showed that the rate of accumulation of N2O in the atmosphere in the late nineteenth and twentieth centuries was greater than that predicted from agricultural inputs limited to fertilizer N and biologically fixed N (Davidson, E. A. 2009 Nat. Geosci. 2, 659-662.). However, by also including soil organic N mineralized following land-use change and NOx deposited from the atmosphere in our estimates of the reactive N entering the agricultural cycle, we have now obtained a good fit between the observed atmospheric N2O concentrations from 1860 to 2000 and those calculated on the basis of a 4 per cent EF for the reactive N.
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Michael Taylor et al.
International Journal of Climatology, forthcoming
Abstract:
Under global warming the Caribbean is projected to be significantly drier by century's end during its primary rainy season from May to November. The PRECIS regional model is used to simulate the end-of-century (2071-2100) manifestation of the Caribbean Low Level Jet (CLLJ) under two Intergovernmental Panel on Climate Change (IPCC) global warming scenarios. The CLLJ is a feature of the Intra-American seas which during its July peak is dynamically linked to a brief mid-summer drying and interruption of the Caribbean rainy season. The regional model captures the CLLJ's present-day spatial and temporal characteristics reasonably well, simulating both the boreal winter (February) and summer (July) peaks. Under global warming there is an intensification of the CLLJ's core strength from May through November. The intensification is such that by October the CLLJ is of comparable core strength to its present-day peak in July. The persistence of the strong CLLJ beyond July and through November is linked to the perpetuation of a dry pattern in the Caribbean in the future. In contrast, the boreal winter manifestation of the CLLJ is largely unaltered in the future.
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Ice-sheet collapse and sea-level rise at the Bølling warming 14,600 years ago
Pierre Deschamps et al.
Nature, 29 March 2012, Pages 559-564
Abstract:
Past sea-level records provide invaluable information about the response of ice sheets to climate forcing. Some such records suggest that the last deglaciation was punctuated by a dramatic period of sea-level rise, of about 20 metres, in less than 500 years. Controversy about the amplitude and timing of this meltwater pulse (MWP-1A) has, however, led to uncertainty about the source of the melt water and its temporal and causal relationships with the abrupt climate changes of the deglaciation. Here we show that MWP-1A started no earlier than 14,650 years ago and ended before 14,310 years ago, making it coeval with the Bølling warming. Our results, based on corals drilled offshore from Tahiti during Integrated Ocean Drilling Project Expedition 310, reveal that the increase in sea level at Tahiti was between 12 and 22 metres, with a most probable value between 14 and 18 metres, establishing a significant meltwater contribution from the Southern Hemisphere. This implies that the rate of eustatic sea-level rise exceeded 40 millimetres per year during MWP-1A.
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Global contraction of Antarctic Bottom Water between the 1980s and 2000s
Sarah Purkey & Gregory Johnson
Journal of Climate, forthcoming
Abstract:
A statistically significant reduction in Antarctic Bottom Water (AABW) volume is quantified between the 1980s and 2000s within the Southern Ocean and along the bottom-most, southern branches of the Meridional Overturning Circulation (MOC). AABW has warmed globally during that time, contributing roughly 10% of the recent total ocean heat uptake. This warming implies a global-scale contraction of AABW. Rates of change in AABW-related circulation are estimated in most of the world's deep ocean basins by finding average rates of volume loss or gain below cold, deep potential temperature (θ) surfaces using all available repeated hydrographic sections. The Southern Ocean is losing water below θ = 0°C at a rate of -8.2 (±2.6) × 106 m3 s-1. This bottom water contraction causes a descent of potential isotherms throughout much of the water column until a near-surface recovery, apparently through a southward surge of Circumpolar Deep Water from the north. To the north, smaller losses of bottom waters are seen along three of the four main northward outflow routes of AABW. Volume and heat budgets below deep, cold θ surfaces within the Brazil and Pacific basins are not in steady state. The observed changes in volume and heat of the coldest waters within these basins could be accounted for by small decreases to the volume transport or small increases to θ of their inflows, or fractional increases in deep mixing. The budget calculations and global contraction pattern are consistent with a global scale slowdown of the bottom, southern limb of the MOC.
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Christian Franzke
International Journal of Climatology, forthcoming
Abstract:
This study examines the daily observed temperature at the Faraday/Vernadsky station in the Antarctic Peninsula for the period February 1947 through January 2011. Faraday/Vernadsky is experiencing a significant warming trend of about 0.6 °C/decade over the last few decades. Concurrently, the magnitude of extremely cold temperatures has reduced while there is no evidence for an increase of the annual maximum temperature. An empirical mode decomposition reveals that most of the temperature variability occurs on intraannual time scales and that changes in the magnitude of the annual cycle can be explained by a simple periodic stochastic process. Extremely cold temperatures below a threshold follow a generalised Pareto distribution (GPD) with a negative shape parameter and thus are bounded. We find that the extremely cold behaviour in the first half of the record is significantly different from the second half. At the same time there is no evident increase of warm temperatures or in the location of the maximum of the temperature probability distribution. These findings provide evidence that at Faraday/Vernadsky, it is the change in the shape of the temperature distribution that has substantially contributed to the observed warming over the last few decades. Furthermore, we find evidence for clustering of extreme cold events and show that they are predictable a few days in advance using a precursor-based prediction scheme.