It's a jungle out there
Drivers for the renaissance of coal
Jan Christoph Steckel, Ottmar Edenhofer & Michael Jakob
Proceedings of the National Academy of Sciences, 21 July 2015, Pages E3775–E3781
Abstract:
Coal was central to the industrial revolution, but in the 20th century it increasingly was superseded by oil and gas. However, in recent years coal again has become the predominant source of global carbon emissions. We show that this trend of rapidly increasing coal-based emissions is not restricted to a few individual countries such as China. Rather, we are witnessing a global renaissance of coal majorly driven by poor, fast-growing countries that increasingly rely on coal to satisfy their growing energy demand. The low price of coal relative to gas and oil has played an important role in accelerating coal consumption since the end of the 1990s. In this article, we show that in the increasingly integrated global coal market the availability of a domestic coal resource does not have a statistically significant impact on the use of coal and related emissions. These findings have important implications for climate change mitigation: If future economic growth of poor countries is fueled mainly by coal, ambitious mitigation targets very likely will become infeasible. Building new coal power plant capacities will lead to lock-in effects for the next few decades. If that lock-in is to be avoided, international climate policy must find ways to offer viable alternatives to coal for developing countries.
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The Distributional Effects of U.S. Clean Energy Tax Credits
Severin Borenstein & Lucas Davis
NBER Working Paper, July 2015
Abstract:
Since 2006, U.S. households have received more than $18 billion in federal income tax credits for weatherizing their homes, installing solar panels, buying hybrid and electric vehicles, and other "clean energy" investments. We use tax return data to examine the socioeconomic characteristics of program recipients. We find that these tax expenditures have gone predominantly to higher-income Americans. The bottom three income quintiles have received about 10% of all credits, while the top quintile has received about 60%. The most extreme is the program aimed at electric vehicles, where we find that the top income quintile has received about 90% of all credits. By comparing to previous work on the distributional consequences of pricing greenhouse gas emissions, we conclude that tax credits are likely to be much less attractive on distributional grounds than market mechanisms to reduce GHGs.
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General Equilibrium Impacts of a Federal Clean Energy Standard
Lawrence Goulder, Marc Hafstead & Roberton Williams
American Economic Journal: Economic Policy, forthcoming
Abstract:
Economists have tended to view emissions pricing (e.g., cap and trade or a carbon tax) as the most cost-effective approach to reducing greenhouse gas emissions. This paper offers a different view. Employing analytical and numerically solved general equilibrium models, it provides plausible conditions under which a more conventional form of regulation — namely, the use of a clean energy standard (CES) — is more cost-effective. The models reveal that the CES distorts factor markets less because it is a smaller implicit tax on factors of production. This advantage more than offsets the disadvantages of the CES when minor emissions reductions are involved.
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Xinsheng Liu et al.
Climatic Change, August 2015, Pages 487-503
Abstract:
Among many potential causes for policymakers’ contention over whether there is a largely unified scientific agreement on global warming and climate change (GWCC), one possible factor, according to the information deficit theory, is that the scientists who testified in congressional hearings might be substantially divided in their views and positions associated with GWCC. To clarify this, we perform content analysis of 1350 testimonies from congressional GWCC hearings over a period of 39 years from 1969 to 2007 and use the data derived from this content analysis to provide an overview of scientist witnesses’ stances on GWCC. The key findings include: (1) among the scientists’ testimonies with an expressed view on whether GWCC is real, a vast majority (86 %) indicates that it is happening; (2) among the scientists’ testimonies with an identified stance on whether GWCC is anthropogenic, a great majority of them (78 %) indicates that GWCC is caused, at least to some degree, by human activity; (3) even under Republican controlled congresses, there is still a supermajority (75 %) - among the scientists’ testimonies with an expressed position on GWCC existence or GWCC cause - that believes that GWCC is real and that GWCC is anthropogenic; (4) most scientists’ testimonies (95 %) endorse pro-action policy to combat GWCC; and (5) the percentages of scientists’ views and positions are consistent across different types of scientist testimony groups. Our findings suggest that the scientific information transmitted to Congress is not substantially different from the general agreement in the climate science community.
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Should We Give Up After Solyndra? Optimal Technology R&D Portfolios under Uncertainty
Mort Webster et al.
NBER Working Paper, July 2015
Abstract:
Global climate change and other environmental challenges require the development of new energy technologies with lower emissions. In the near-term, R&D investments, either by government or the private sector, can bring down the costs of these lower emission technologies. However, the results of R&D are uncertain, and there are many potential technologies that may turn out to play an effective role in the future energy mix. In this paper, we address the problem of allocating R&D across technologies under uncertainty. Specifically, given two technologies, one with lower costs at present, but the other with greater uncertainty in the returns to R&D, how should one allocate the R&D budget? We develop a multi-stage stochastic dynamic programming version of an integrated assessment model of climate and economy that represents endogenous technological change through R&D decisions for two substitutable non-carbon backstop technologies. Using the model, we demonstrate that near-term R&D into the higher cost technology is justified, and that the amount of R&D into the high cost technology increases with both the variance in the uncertainty in returns to R&D and with the skewness of the uncertainty. We also present an illustrative case study of wind and solar photovoltaic technologies, and show that poor R&D results in early periods do not necessarily mean that investment should not continue.
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Mohamad Hejazi et al.
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
There is evidence that warming leads to greater evapotranspiration and surface drying, thus contributing to increasing intensity and duration of drought and implying that mitigation would reduce water stresses. However, understanding the overall impact of climate change mitigation on water resources requires accounting for the second part of the equation, i.e., the impact of mitigation-induced changes in water demands from human activities. By using integrated, high-resolution models of human and natural system processes to understand potential synergies and/or constraints within the climate–energy–water nexus, we show that in the United States, over the course of the 21st century and under one set of consistent socioeconomics, the reductions in water stress from slower rates of climate change resulting from emission mitigation are overwhelmed by the increased water stress from the emissions mitigation itself. The finding that the human dimension outpaces the benefits from mitigating climate change is contradictory to the general perception that climate change mitigation improves water conditions. This research shows the potential for unintended and negative consequences of climate change mitigation.
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Climate variability and international migration: An empirical analysis
Nicola Coniglio & Giovanni Pesce
Environment and Development Economics, August 2015, Pages 434-468
Abstract:
Is international migration an adaptation strategy to sudden or gradual climatic shocks? In this paper we investigate the direct and the indirect role of climatic shocks in developing countries as a determinant of out-migration flows toward rich OECD countries in the period 1990–2001. Contrarily to the bulk of existing studies, we use a macro approach and explicitly consider the heterogeneity of climatic shocks (type, size, sign of shocks and seasonal effects). Our results show that the occurrence of adverse climatic events in origin countries has significative direct and indirect effects on out-migration from poor to rich countries.
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Historically unprecedented global glacier decline in the early 21st century
Michael Zemp et al.
Journal of Glaciology, forthcoming
Abstract:
Observations show that glaciers around the world are in retreat and losing mass. Internationally coordinated for over a century, glacier monitoring activities provide an unprecedented dataset of glacier observations from ground, air and space. Glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass-balance data relating to the impact that glaciers exercise on global sea-level fluctuations or on regional runoff. In this study we provide an overview and analysis of the main observational datasets compiled by the World Glacier Monitoring Service (WGMS). The dataset on glacier front variations (~42 000 since 1600) delivers clear evidence that centennial glacier retreat is a global phenomenon. Intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the Little Ice Age (or Holocene). Glaciological and geodetic observations (~5200 since 1850) show that the rates of early 21st-century mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history, as indicated also in reconstructions from written and illustrated documents. This strong imbalance implies that glaciers in many regions will very likely suffer further ice loss, even if climate remains stable.
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Solar Geoengineering, Uncertainty, and the Price of Carbon
Garth Heutel, Juan Moreno Cruz & Soheil Shayegh
NBER Working Paper, July 2015
Abstract:
We consider the socially optimal use of solar geoengineering to manage climate change. Solar geoengineering can reduce damages from atmospheric greenhouse gas concentrations, potentially more cheaply than reducing emissions. If so, optimal policy includes less abatement than recommended by models that ignore solar geoengineering, and the price of carbon is lower. Solar geoengineering reduces temperature but does not reduce atmospheric or ocean carbon concentrations, and that carbon may cause damages apart from temperature increases. Finally, uncertainty over climate change and solar geoengineering alters the optimal deployment of solar geoengineering. We explore these issues with an analytical model and a numerical simulation. The price of carbon is 30%-45% lower than the price recommended in a model without geoengineering, depending on the parameterizations of geoengineering costs and benefits. Carbon concentrations are higher but temperature is lower when allowing for solar geoengineering. The optimal amount of solar geoengineering is more sensitive to climate uncertainty than is the optimal amount of abatement.
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Recent hiatus caused by decadal shift in Indo-Pacific heating
Veronica Nieves, Josh Willis & William Patzert
Science, 31 July 2015, Pages 532-535
Abstract:
Recent modeling studies have proposed different scenarios to explain the slowdown in surface temperature warming in the most recent decade. Some of these studies seem to support the idea of internal variability and/or rearrangement of heat between the surface and the ocean interior. Others suggest that radiative forcing might also play a role. Our examination of observational data over the past two decades shows some significant differences when compared to model results from reanalyses and provides the most definitive explanation of how the heat was redistributed. We find that cooling in the top 100-meter layer of the Pacific Ocean was mainly compensated for by warming in the 100- to 300-meter layer of the Indian and Pacific Oceans in the past decade since 2003.
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Change points of global temperature
Niamh Cahill, Stefan Rahmstorf & Andrew Parnell
Environmental Research Letters, August 2015
Abstract:
We aim to address the question of whether or not there is a significant recent 'hiatus', 'pause' or 'slowdown' of global temperature rise. Using a statistical technique known as change point (CP) analysis we identify the changes in four global temperature records and estimate the rates of temperature rise before and after these changes occur. For each record the results indicate that three CPs are enough to accurately capture the variability in the data with no evidence of any detectable change in the global warming trend since ~1970. We conclude that the term 'hiatus' or 'pause' cannot be statistically justified.
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Decadal acidification in the water masses of the Atlantic Ocean
Aida Ríos et al.
Proceedings of the National Academy of Sciences, 11 August 2015, Pages 9950–9955
Abstract:
Global ocean acidification is caused primarily by the ocean’s uptake of CO2 as a consequence of increasing atmospheric CO2 levels. We present observations of the oceanic decrease in pH at the basin scale (50°S–36°N) for the Atlantic Ocean over two decades (1993–2013). Changes in pH associated with the uptake of anthropogenic CO2 (ΔpHCant) and with variations caused by biological activity and ocean circulation (ΔpHNat) are evaluated for different water masses. Output from an Institut Pierre Simon Laplace climate model is used to place the results into a longer-term perspective and to elucidate the mechanisms responsible for pH change. The largest decreases in pH (∆pH) were observed in central, mode, and intermediate waters, with a maximum ΔpH value in South Atlantic Central Waters of −0.042 ± 0.003. The ΔpH trended toward zero in deep and bottom waters. Observations and model results show that pH changes generally are dominated by the anthropogenic component, which accounts for rates between −0.0015 and −0.0020/y in the central waters. The anthropogenic and natural components are of the same order of magnitude and reinforce one another in mode and intermediate waters over the time period. Large negative ΔpHNat values observed in mode and intermediate waters are driven primarily by changes in CO2 content and are consistent with (i) a poleward shift of the formation region during the positive phase of the Southern Annular Mode in the South Atlantic and (ii) an increase in the rate of the water mass formation in the North Atlantic.
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Increased record-breaking precipitation events under global warming
Jascha Lehmann, Dim Coumou & Katja Frieler
Climatic Change, forthcoming
Abstract:
In the last decade record-breaking rainfall events have occurred in many places around the world causing severe impacts to human society and the environment including agricultural losses and floodings. There is now medium confidence that human-induced greenhouse gases have contributed to changes in heavy precipitation events at the global scale. Here, we present the first analysis of record-breaking daily rainfall events using observational data. We show that over the last three decades the number of record-breaking events has significantly increased in the global mean. Globally, this increase has led to 12 % more record-breaking rainfall events over 1981–2010 compared to those expected in stationary time series. The number of record-breaking rainfall events peaked in 2010 with an estimated 26 % chance that a new rainfall record is due to long-term climate change. This increase in record-breaking rainfall is explained by a statistical model which accounts for the warming of air and associated increasing water holding capacity only. Our results suggest that whilst the number of rainfall record-breaking events can be related to natural multi-decadal variability over the period from 1901 to 1980, observed record-breaking rainfall events significantly increased afterwards consistent with rising temperatures.
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Drivers of the US CO2 emissions 1997–2013
Kuishuang Feng et al.
Nature Communications, July 2015
Abstract:
Fossil fuel CO2 emissions in the United States decreased by ~11% between 2007 and 2013, from 6,023 to 5,377 Mt. This decline has been widely attributed to a shift from the use of coal to natural gas in US electricity production. However, the factors driving the decline have not been quantitatively evaluated; the role of natural gas in the decline therefore remains speculative. Here we analyse the factors affecting US emissions from 1997 to 2013. Before 2007, rising emissions were primarily driven by economic growth. After 2007, decreasing emissions were largely a result of economic recession with changes in fuel mix (for example, substitution of natural gas for coal) playing a comparatively minor role. Energy–climate policies may, therefore, be necessary to lock-in the recent emissions reductions and drive further decarbonization of the energy system as the US economy recovers and grows.
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Decreasing US aridity in a warming climate
J.M. Finkel, L.M. Canel-Katz & J.I. Katz
International Journal of Climatology, forthcoming
Abstract:
The mean North American and world climates have warmed since the 19th century following the anthropogenic emission of large quantities of greenhouse gases. It has been suggested that this warming may increase the frequency or severity of droughts. We define a quantitative and objective aridity index that describes the precipitation forcing function of drought. Using the extensive historical database of precipitation records, we evaluate changes in the aridity in the 48 contiguous United States. The area-averaged mean fractional rate of change of aridity of 1218 sites in the period 1893–2013 was (−6.6 ± 0.4) × 10− 4 per year; the 48 contiguous United States became less arid. The rate of decrease of aridity was roughly consistent with expectations from the Clausius–Clapeyron relation and the rate of warming. The fractional rate of change of aridity was nearly uncorrelated with the aridity itself, but there were regional differences: many Western and coastal Southeastern sites showed increasing aridity, but regions of rapidly decreasing aridity were found in a band 85∘–100∘W and the Northeast.
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Projected changes in regional climate extremes arising from Arctic sea ice loss
James Screen, Clara Deser & Lantao Sun
Environmental Research Letters, August 2015
Abstract:
The decline in Arctic sea ice cover has been widely documented and it is clear that this change is having profound impacts locally. An emerging and highly uncertain area of scientific research, however, is whether such Arctic change has a tangible effect on weather and climate at lower latitudes. Of particular societal relevance is the open question: will continued Arctic sea ice loss make mid-latitude weather more extreme? Here we analyse idealized atmospheric general circulation model simulations, using two independent models, both forced by projected Arctic sea ice loss in the late twenty-first century. We identify robust projected changes in regional temperature and precipitation extremes arising solely due to Arctic sea ice loss. The likelihood and duration of cold extremes are projected to decrease over high latitudes and over central and eastern North America, but to increase over central Asia. Hot extremes are projected to increase in frequency and duration over high latitudes. The likelihood and severity of wet extremes are projected to increase over high latitudes, the Mediterranean and central Asia; and their intensity is projected to increase over high latitudes and central and eastern Asia. The number of dry days over mid-latitude Eurasia and dry spell duration over high latitudes are both projected to decrease. There is closer model agreement for projected changes in temperature extremes than for precipitation extremes. Overall, we find that extreme weather over central and eastern North America is more sensitive to Arctic sea ice loss than over other mid-latitude regions. Our results are useful for constraining the role of Arctic sea ice loss in shifting the odds of extreme weather, but must not be viewed as deterministic projections, as they do not account for drivers other than Arctic sea ice loss.
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Evaluating changes in season length, onset, and end dates across the United States (1948–2012)
Michael Allen & Scott Sheridan
International Journal of Climatology, forthcoming
Abstract:
Discussed in a global context, the issue of scale is important to consider as it relates to climate change. As climatological studies utilize temporally and spatially static definitions of seasonal definitions, the understanding of seasonal change may be limited by the way in which seasons are defined. This research serves as a challenge to this perspective by examining the changes in seasons by incorporating variability into the way in which seasons are defined. Temporally and spatially variable seasons were defined based on thresholds of apparent temperature and upper-level circulation patterns for the period 1948–2012. Using 60 US surface stations, two apparent air temperature metrics were used to define seasons that vary spatially and temporally. Stations represented major cities found in the contiguous United States. A large-scale circulation approach utilized synoptic categorizations based on 250-mb geopotential heights from the NCEP-NCAR reanalysis (NNR) as a metric of seasonal delineation. In this method, seasons varied temporally but not spatially. Despite the different methodological approaches, consistent trends were found. Since 1948, late starts of autumn and winter have been observed while earlier onsets of spring and summer have taken place. For the individual stations, the largest shifts occurred along coasts and in larger, more urbanized environments. Individual locations also showed increased variability in start date, and significant changes were found for all four seasons in the circulation approach. Seasons have been shown to be important for a variety of processes including phenological responses and human adaptation to extreme temperature environments; therefore, the consideration of season variability may be appropriate for future climatological research.
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Jiali Wang & Veerabhadra Kotamarthi
Earth's Future, forthcoming
Abstract:
This study performs high-spatial-resolution (12 km) Weather Research and Forecasting (WRF) simulations over a very large domain (7200 km × 6180 km, covering much of North America) to explore changes in mean and extreme precipitation in the mid and late 21st century under Representative Concentration Pathways 4.5 (RCP 4.5) and 8.5 (RCP 8.5). We evaluate WRF model performance for a historical simulation and future projections, applying the Community Climate System Model version 4 (CCSM4) as initial and boundary conditions with and without a bias correction. WRF simulations using boundary and initial conditions from both versions of CCSM4 show smaller biases versus evaluation data sets than does CCSM4 over western North America. WRF simulations also improve spatial details of precipitation over much of North America. However, driving the WRF with the bias-corrected CCSM4 does not always reduce the bias. WRF-projected changes in precipitation include decreasing intensity over the U.S. Southwest, increasing intensity over the eastern United Sates and most of Canada, and an increase in the number of days with heavy precipitation over much of North America. Projected precipitation changes are more evident in the late 21st century than the mid 21st century, and they are more evident under RCP 8.5 than RCP 4.5 in the late 21st century. Uncertainties in the projected changes in precipitation due to different warming scenarios are non-negligible. Differences in summer precipitation changes between WRF and CCSM4 are significant over most of the United States.
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Mark Lesser & Jason Fridley
International Journal of Climatology, forthcoming
Abstract:
Organisms in montane environments are sensitive to fine-scale climatic variation associated with highly dissected topography, yet few studies have examined the sensitivity of different landscape positions to climate change. We downscaled biologically significant temperature variables to below-canopy 30 m resolution and assessed temporal trends from 1980 to 2011 across elevation and topographic gradients in Great Smoky Mountains National Park (GSMNP; Tennessee and North Carolina, USA) using a previously developed empirical model derived from a 120-sensor temperature network. Additionally, we assessed GSMNP climate trends from 1900 using six historical climate records from the region and an additional eight records from 1980, spanning the Park's elevation gradient. Regional temperatures increased through the 1980s and 1990s, but currently remain at or below those recorded in the early to mid-20th century and are strongly associated with different phases of the North Atlantic Oscillation. In contrast, annual and growing season precipitation steadily rose during the past century. Landscape-scale analysis showed that rates of change for maximum seasonal temperatures, frost-free days (FFD), and growing degree days were strongly mediated by topographic position, with high-elevation ridges having greater rates of maximum temperature increases, whereas high-elevation near-stream positions showed the least amount of increase in FFD and growing degree days. Most importantly, we show how modelled differences in rates of climatic change based on landscape position could have significant ecological effects in this biologically significant region, depending on how organisms respond to particular climate factors. Organisms that depend on growing season length may experience the largest climate effects at the lowest elevations, while those that depend on warm days in spring and autumn for particular phenological processes will experience the largest shifts at high-elevation ridges.
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Impacts of climate change on electric power supply in the Western United States
Matthew Bartos & Mikhail Chester
Nature Climate Change, August 2015, Pages 748–752
Abstract:
Climate change may constrain future electricity generation capacity by increasing the incidence of extreme heat and drought events. We estimate reductions to generating capacity in the Western United States based on long-term changes in streamflow, air temperature, water temperature, humidity and air density. We simulate these key parameters over the next half-century by joining downscaled climate forcings with a hydrologic modelling system. For vulnerable power stations (46% of existing capacity), climate change may reduce average summertime generating capacity by 1.1–3.0%, with reductions of up to 7.2–8.8% under a ten-year drought. At present, power providers do not account for climate impacts in their development plans, meaning that they could be overestimating their ability to meet future electricity needs.