Reaching for the sky
The Wrong Solution at the Right Time: The Failure of the Kyoto Protocol on Climate Change
Amanda Rosen
Politics & Policy, February 2015, Pages 30–58
Abstract:
This article argues that the Kyoto Protocol on climate change is a fundamentally flawed agreement that set back solutions on climate change by two decades. Using a systematic framework focused on compliance, efficiency, and effectiveness, I analyze the Kyoto Protocol and argue it is a clear case of institutional failure, with the design itself bearing substantial blame for this outcome. The study points to how particular features of the Protocol — its short time frame for action, binding targets, emission reduction measures, and provision for future commitment periods — have resulted in short-sighted behavior by member states and path-dependent structures that failed to make a substantial impact on the climate problem.
---------------------
Calculation of a Population Externality
Henning Bohn & Charles Stuart
American Economic Journal: Economic Policy, forthcoming
Abstract:
It is known that when people generate externalities, a birth also generates an externality and efficiency requires a Pigou tax/subsidy on having children. The size of the externality from a birth is important for studying policy. We calculate the size of this “population externality” in a specific case: we consider a maintained hypothesis that greenhouse gas emissions are a serious problem and assume government reacts by optimally restricting emissions. Calculated population externalities are large under many assumptions.
---------------------
Near-term acceleration in the rate of temperature change
Steven Smith et al.
Nature Climate Change, forthcoming
Abstract:
Anthropogenically driven climate changes, which are expected to impact human and natural systems, are often expressed in terms of global-mean temperature. The rate of climate change over multi-decadal scales is also important, with faster rates of change resulting in less time for human and natural systems to adapt. We find that present trends in greenhouse-gas and aerosol emissions are now moving the Earth system into a regime in terms of multi-decadal rates of change that are unprecedented for at least the past 1,000 years. The rate of global-mean temperature increase in the CMIP5 archive over 40-year periods increases to 0.25 ± 0.05 °C (1σ) per decade by 2020, an average greater than peak rates of change during the previous one to two millennia. Regional rates of change in Europe, North America and the Arctic are higher than the global average. Research on the impacts of such near-term rates of change is urgently needed.
---------------------
Climate Sensitivity Uncertainty: When is Good News Bad?
Mark Freeman, Gernot Wagner & Richard Zeckhauser
NBER Working Paper, January 2015
Abstract:
Climate change is real and dangerous. Exactly how bad it will get, however, is uncertain. Uncertainty is particularly relevant for estimates of one of the key parameters: equilibrium climate sensitivity—how eventual temperatures will react as atmospheric carbon dioxide concentrations double. Despite significant advances in climate science and increased confidence in the accuracy of the range itself, the “likely” range has been 1.5-4.5°C for over three decades. In 2007, the Intergovernmental Panel on Climate Change (IPCC) narrowed it to 2-4.5°C, only to reverse its decision in 2013, reinstating the prior range. In addition, the 2013 IPCC report removed prior mention of 3°C as the “best estimate.” We interpret the implications of the 2013 IPCC decision to lower the bottom of the range and excise a best estimate. Intuitively, it might seem that a lower bottom would be good news. Here we ask: When might apparently good news about climate sensitivity in fact be bad news? The lowered bottom value also implies higher uncertainty about the temperature increase, a definite bad. Under reasonable assumptions, both the lowering of the lower bound and the removal of the “best estimate” may well be bad news.
---------------------
Climate change in the Fertile Crescent and implications of the recent Syrian drought
Colin Kelley et al.
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
Before the Syrian uprising that began in 2011, the greater Fertile Crescent experienced the most severe drought in the instrumental record. For Syria, a country marked by poor governance and unsustainable agricultural and environmental policies, the drought had a catalytic effect, contributing to political unrest. We show that the recent decrease in Syrian precipitation is a combination of natural variability and a long-term drying trend, and the unusual severity of the observed drought is here shown to be highly unlikely without this trend. Precipitation changes in Syria are linked to rising mean sea-level pressure in the Eastern Mediterranean, which also shows a long-term trend. There has been also a long-term warming trend in the Eastern Mediterranean, adding to the drawdown of soil moisture. No natural cause is apparent for these trends, whereas the observed drying and warming are consistent with model studies of the response to increases in greenhouse gases. Furthermore, model studies show an increasingly drier and hotter future mean climate for the Eastern Mediterranean. Analyses of observations and model simulations indicate that a drought of the severity and duration of the recent Syrian drought, which is implicated in the current conflict, has become more than twice as likely as a consequence of human interference in the climate system.
---------------------
The changing nature of flooding across the central United States
Iman Mallakpour & Gabriele Villarini
Nature Climate Change, March 2015, Pages 250–254
Abstract:
In the twentieth and twenty-first centuries, flooding has taken a devastating societal and economic toll on the central United States, contributing to dozens of fatalities and causing billions of dollars in damage. As a warmer atmosphere can hold more moisture (the Clausius–Clapeyron relation), a pronounced increase in intense rainfall events is included in models of future climate. Therefore, it is crucial to examine whether the magnitude and/or frequency of flood events is remaining constant or has been changing over recent decades. If either or both of these attributes have changed over time, it is imperative that we understand the underlying mechanisms that are responsible. Here, we show that while observational records (774 stream gauge stations) from the central United States present limited evidence of significant changes in the magnitude of floodpeaks, strong evidence points to an increasing frequency of flooding. These changes in flood hydrology result from changes in both seasonal rainfall and temperature across this region.
---------------------
Geoengineering and Climate Change Polarization: Testing a Two-Channel Model of Science Communication
Dan Kahan et al.
ANNALS of the American Academy of Political and Social Science, March 2015, Pages 192-222
Abstract:
The cultural cognition thesis posits that individuals rely extensively on cultural meanings in forming perceptions of risk. The logic of the cultural cognition thesis suggests that a two-channel science communication strategy, combining information content (“Channel 1”) with cultural meanings (“Channel 2”), could promote open-minded assessment of information across diverse communities. We test this kind of communication strategy in a two-nation (United States, n = 1,500; England, n = 1,500) study, in which scientific information content on climate change was held constant while the cultural meaning of that information was experimentally manipulated. We found that cultural polarization over the validity of climate change science is offset by making citizens aware of the potential contribution of geoengineering as a supplement to restriction of CO2 emissions. We also tested the hypothesis, derived from a competing model of science communication, that exposure to information on geoengineering would lead citizens to discount climate change risks generally. Contrary to this hypothesis, we found that subjects exposed to information about geoengineering were slightly more concerned about climate change risks than those assigned to a control condition.
---------------------
Expecting the Unexpected: Emissions Uncertainty and Environmental Market Design
Severin Borenstein et al.
NBER Working Paper, March 2015
Abstract:
We analyze the demand for emissions allowances and the supply of allowances and abatement opportunities in California's 2013-2020 cap and trade market for greenhouse gases (GHG). We estimate a cointegrated vector autoregression for the main drivers of greenhouse gas emissions using annual data from 1990 to 2011. We use these estimates to forecast businss-as-usual (BAU) emissions during California's program and the impact of the state's other GHG reduction programs. We then consider additional price-responsive and price-inelastic activities that will affect the supply/demand balance in the allowance market. We show that there is significant uncertainty in the BAU emissions levels due to uncertainty in economic growth and other factors. Our analysis also suggests that most of the planned abatement will not be very sensitive to the price of allowances, creating a steep abatement supply curve. The combination of BAU emissions uncertainty and inelastic abatement supply implies a high probability that the price of allowances in California will either be at the price floor, or high enough to trigger a safety valve mechanism called the Allowance Price Containment Reserve (APCR). We estimate a low probability that the price would end up in an intermediate range between the price floor and the APCR. The analysis suggests that cap-and-trade markets, as they have been established in California, the EU and elsewhere may be more likely to experience price volatility and extreme low or high prices than is generally recognized.
---------------------
Anthropogenic warming has increased drought risk in California
Noah Diffenbaugh, Daniel Swain & Danielle Touma
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
California is currently in the midst of a record-setting drought. The drought began in 2012 and now includes the lowest calendar-year and 12-mo precipitation, the highest annual temperature, and the most extreme drought indicators on record. The extremely warm and dry conditions have led to acute water shortages, groundwater overdraft, critically low streamflow, and enhanced wildfire risk. Analyzing historical climate observations from California, we find that precipitation deficits in California were more than twice as likely to yield drought years if they occurred when conditions were warm. We find that although there has not been a substantial change in the probability of either negative or moderately negative precipitation anomalies in recent decades, the occurrence of drought years has been greater in the past two decades than in the preceding century. In addition, the probability that precipitation deficits co-occur with warm conditions and the probability that precipitation deficits produce drought have both increased. Climate model experiments with and without anthropogenic forcings reveal that human activities have increased the probability that dry precipitation years are also warm. Further, a large ensemble of climate model realizations reveals that additional global warming over the next few decades is very likely to create ∼100% probability that any annual-scale dry period is also extremely warm. We therefore conclude that anthropogenic warming is increasing the probability of co-occurring warm–dry conditions like those that have created the acute human and ecosystem impacts associated with the “exceptional” 2012–2014 drought in California.
---------------------
Observational determination of surface radiative forcing by CO2 from 2000 to 2010
D.R. Feldman et al.
Nature, forthcoming
Abstract:
The climatic impact of CO2 and other greenhouse gases is usually quantified in terms of radiative forcing, calculated as the difference between estimates of the Earth’s radiation field from pre-industrial and present-day concentrations of these gases. Radiative transfer models calculate that the increase in CO2 since 1750 corresponds to a global annual-mean radiative forcing at the tropopause of 1.82 ± 0.19 W m−2. However, despite widespread scientific discussion and modelling of the climate impacts of well-mixed greenhouse gases, there is little direct observational evidence of the radiative impact of increasing atmospheric CO2. Here we present observationally based evidence of clear-sky CO2 surface radiative forcing that is directly attributable to the increase, between 2000 and 2010, of 22 parts per million atmospheric CO2. The time series of this forcing at the two locations — the Southern Great Plains and the North Slope of Alaska — are derived from Atmospheric Emitted Radiance Interferometer spectra together with ancillary measurements and thoroughly corroborated radiative transfer calculations. The time series both show statistically significant trends of 0.2 W m−2 per decade (with respective uncertainties of ±0.06 W m−2 per decade and ±0.07 W m−2 per decade) and have seasonal ranges of 0.1–0.2 W m−2. This is approximately ten per cent of the trend in downwelling longwave radiation. These results confirm theoretical predictions of the atmospheric greenhouse effect due to anthropogenic emissions, and provide empirical evidence of how rising CO2 levels, mediated by temporal variations due to photosynthesis and respiration, are affecting the surface energy balance.
---------------------
Changes in observed climate extremes in global urban areas
Vimal Mishra et al.
Environmental Research Letters, February 2015
Abstract:
Climate extremes have profound implications for urban infrastructure and human society, but studies of observed changes in climate extremes over the global urban areas are few, even though more than half of the global population now resides in urban areas. Here, using observed station data for 217 urban areas across the globe, we show that these urban areas have experienced significant increases (p-value <0.05) in the number of heat waves during the period 1973–2012, while the frequency of cold waves has declined. Almost half of the urban areas experienced significant increases in the number of extreme hot days, while almost 2/3 showed significant increases in the frequency of extreme hot nights. Extreme windy days declined substantially during the last four decades with statistically significant declines in about 60% in the urban areas. Significant increases (p-value <0.05) in the frequency of daily precipitation extremes and in annual maximum precipitation occurred at smaller fractions (17 and 10% respectively) of the total urban areas, with about half as many urban areas showing statistically significant downtrends as uptrends. Changes in temperature and wind extremes, estimated as the result of a 40 year linear trend, differed for urban and non-urban pairs, while changes in indices of extreme precipitation showed no clear differentiation for urban and selected non-urban stations.
---------------------
Questionnaire Design Effects in Climate Change Surveys: Implications for the Partisan Divide
Jonathon Schuldt, Sungjong Roh & Norbert Schwarz
ANNALS of the American Academy of Political and Social Science, March 2015, Pages 67-85
Abstract:
Despite strong agreement among scientists, public opinion surveys reveal wide partisan disagreement on climate issues in the United States. We suggest that this divide may be exaggerated by questionnaire design variables. Following a brief literature review, we report on a national survey experiment involving U.S. Democrats and Republicans (n = 2,041) (fielded August 25–September 5, 2012) that examined the effects of question wording and order on the belief that climate change exists, perceptions of scientific consensus, and support for limiting greenhouse gas emissions. Wording a questionnaire in terms of “global warming” (versus “climate change”) reduced Republicans’ (but not Democrats’) existence beliefs and weakened perceptions of the scientific consensus for both groups. Moreover, “global warming” reduced Republicans’ support for limiting greenhouse gases when this question immediately followed personal existence beliefs but not when the scientific consensus question intervened. We highlight the importance of attending to questionnaire design in the analysis of partisan differences.
---------------------
Increased frequency of extreme La Niña events under greenhouse warming
Wenju Cai et al.
Nature Climate Change, February 2015, Pages 132–137
Abstract:
The El Niño/Southern Oscillation is Earth’s most prominent source of interannual climate variability, alternating irregularly between El Niño and La Niña, and resulting in global disruption of weather patterns, ecosystems, fisheries and agriculture. The 1998–1999 extreme La Niña event that followed the 1997–1998 extreme El Niño event switched extreme El Niño-induced severe droughts to devastating floods in western Pacific countries, and vice versa in the southwestern United States. During extreme La Niña events, cold sea surface conditions develop in the central Pacific, creating an enhanced temperature gradient from the Maritime continent to the central Pacific. Recent studies have revealed robust changes in El Niño characteristics in response to simulated future greenhouse warming, but how La Niña will change remains unclear. Here we present climate modelling evidence, from simulations conducted for the Coupled Model Intercomparison Project phase 5, for a near doubling in the frequency of future extreme La Niña events, from one in every 23 years to one in every 13 years. This occurs because projected faster mean warming of the Maritime continent than the central Pacific, enhanced upper ocean vertical temperature gradients, and increased frequency of extreme El Niño events are conducive to development of the extreme La Niña events. Approximately 75% of the increase occurs in years following extreme El Niño events, thus projecting more frequent swings between opposite extremes from one year to the next.
---------------------
Nonlinear regional warming with increasing CO2 concentrations
Peter Good et al.
Nature Climate Change, February 2015, Pages 138–142
Abstract:
When considering adaptation measures and global climate mitigation goals, stakeholders need regional-scale climate projections, including the range of plausible warming rates. To assist these stakeholders, it is important to understand whether some locations may see disproportionately high or low warming from additional forcing above targets such as 2 K. There is a need to narrow uncertainty in this nonlinear warming, which requires understanding how climate changes as forcings increase from medium to high levels. However, quantifying and understanding regional nonlinear processes is challenging. Here we show that regional-scale warming can be strongly superlinear to successive CO2 doublings, using five different climate models. Ensemble-mean warming is superlinear over most land locations. Further, the inter-model spread tends to be amplified at higher forcing levels, as nonlinearities grow — especially when considering changes per kelvin of global warming. Regional nonlinearities in surface warming arise from nonlinearities in global-mean radiative balance, the Atlantic meridional overturning circulation, surface snow/ice cover and evapotranspiration. For robust adaptation and mitigation advice, therefore, potentially avoidable climate change (the difference between business-as-usual and mitigation scenarios) and unavoidable climate change (change under strong mitigation scenarios) may need different analysis methods.
---------------------
Rising temperatures reduce global wheat production
S. Asseng et al.
Nature Climate Change, February 2015, Pages 143–147
Abstract:
Crop models are essential tools for assessing the threat of climate change to local and global food production. Present models used to predict wheat grain yield are highly uncertain when simulating how crops respond to temperature. Here we systematically tested 30 different wheat crop models of the Agricultural Model Intercomparison and Improvement Project against field experiments in which growing season mean temperatures ranged from 15 °C to 32 °C, including experiments with artificial heating. Many models simulated yields well, but were less accurate at higher temperatures. The model ensemble median was consistently more accurate in simulating the crop temperature response than any single model, regardless of the input information used. Extrapolating the model ensemble temperature response indicates that warming is already slowing yield gains at a majority of wheat-growing locations. Global wheat production is estimated to fall by 6% for each °C of further temperature increase and become more variable over space and time.
---------------------
Ehsan Eyshi Rezaei, Stefan Siebert & Frank Ewert
Environmental Research Letters, February 2015
Abstract:
Higher temperatures during the growing season are likely to reduce crop yields with implications for crop production and food security. The negative impact of heat stress has also been predicted to increase even further for cereals such as wheat under climate change. Previous empirical modeling studies have focused on the magnitude and frequency of extreme events during the growth period but did not consider the effect of higher temperature on crop phenology. Based on an extensive set of climate and phenology observations for Germany and period 1951–2009, interpolated to 1 × 1 km resolution and provided as supplementary data to this article (available at stacks.iop.org/ERL/10/024012/mmedia), we demonstrate a strong relationship between the mean temperature in spring and the day of heading (DOH) of winter wheat. We show that the cooling effect due to the 14 days earlier DOH almost fully compensates for the adverse effect of global warming on frequency and magnitude of crop heat stress. Earlier heading caused by the warmer spring period can prevent exposure to extreme heat events around anthesis, which is the most sensitive growth stage to heat stress. Consequently, the intensity of heat stress around anthesis in winter crops cultivated in Germany may not increase under climate change even if the number and duration of extreme heat waves increase. However, this does not mean that global warning would not harm crop production because of other impacts, e.g. shortening of the grain filling period. Based on the trends for the last 34 years in Germany, heat stress (stress thermal time) around anthesis would be 59% higher in year 2009 if the effect of high temperatures on accelerating wheat phenology were ignored. We conclude that climate impact assessments need to consider both the effect of high temperature on grain set at anthesis but also on crop phenology.
---------------------
Adaptive potential of a Pacific salmon challenged by climate change
Nicolas Muñoz et al.
Nature Climate Change, February 2015, Pages 163–166
Abstract:
Pacific salmon provide critical sustenance for millions of people worldwide and have far-reaching impacts on the productivity of ecosystems. Rising temperatures now threaten the persistence of these important fishes, yet it remains unknown whether populations can adapt. Here, we provide the first evidence that a Pacific salmon has both physiological and genetic capacities to increase its thermal tolerance in response to rising temperatures. In juvenile chinook salmon (Oncorhynchus tshawytscha), a 4 °C increase in developmental temperature was associated with a 2 °C increase in key measures of the thermal performance of cardiac function. Moreover, additive genetic effects significantly influenced several measures of cardiac capacity, indicative of heritable variation on which selection can act. However, a lack of both plasticity and genetic variation was found for the arrhythmic temperature of the heart, constraining this upper thermal limit to a maximum of 24.5 ± 2.2 °C. Linking this constraint on thermal tolerance with present-day river temperatures and projected warming scenarios, we predict a 17% chance of catastrophic loss in the population by 2100 based on the average warming projection, with this chance increasing to 98% in the maximum warming scenario. Climate change mitigation is thus necessary to ensure the future viability of Pacific salmon populations.
---------------------
William Lau & Kyu-Myong Kim
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
In this paper, we investigate changes in the Hadley Circulation (HC) and their connections to increased global dryness (suppressed rainfall and reduced tropospheric relative humidity) under CO2 warming from Coupled Model Intercomparison Project Phase 5 (CMIP5) model projections. We find a strengthening of the HC manifested in a “deep-tropics squeeze” (DTS), i.e., a deepening and narrowing of the convective zone, enhanced ascent, increased high clouds, suppressed low clouds, and a rise of the level of maximum meridional mass outflow in the upper troposphere (200−100 hPa) of the deep tropics. The DTS induces atmospheric moisture divergence and reduces tropospheric relative humidity in the tropics and subtropics, in conjunction with a widening of the subsiding branches of the HC, resulting in increased frequency of dry events in preferred geographic locations worldwide. Among various water-cycle parameters examined, global dryness is found to have the highest signal-to-noise ratio. Our results provide a physical basis for inferring that greenhouse warming is likely to contribute to the observed prolonged droughts worldwide in recent decades.
---------------------
Response of double cropping suitability to climate change in the United States
Christopher Seifert & David Lobell
Environmental Research Letters, February 2015
Abstract:
In adapting US agriculture to the climate of the 21st century, a key unknown is whether cropping frequency may increase, helping to offset projected negative yield impacts in major production regions. Combining daily weather data and crop phenology models, we find that cultivated area in the US suited to dryland winter wheat–soybeans, the most common double crop (DC) system, increased by up to 28% from 1988 to 2012. Changes in the observed distribution of DC area over the same period agree well with this suitability increase, evidence consistent with climate change playing a role in recent DC expansion in phenologically constrained states. We then apply the model to projections of future climate under the RCP45 and RCP85 scenarios and estimate an additional 126–239% increase, respectively, in DC area. Sensitivity tests reveal that in most instances, increases in mean temperature are more important than delays in fall freeze in driving increased DC suitability. The results suggest that climate change will relieve phenological constraints on wheat–soy DC systems over much of the United States, though it should be recognized that impacts on corn and soybean yields in this region are expected to be negative and larger in magnitude than the 0.4–0.75% per decade benefits we estimate here for double cropping.
---------------------
Citizens’, Scientists’, and Policy Advisors’ Beliefs about Global Warming
Toby Bolsen, James Druckman & Fay Lomax Cook
ANNALS of the American Academy of Political and Social Science, March 2015, Pages 271-295
Abstract:
Numerous factors shape citizens’ beliefs about global warming, but there is very little research that compares the views of the public with key actors in the policymaking process. We analyze data from simultaneous and parallel surveys of (1) the U.S. public, (2) scientists who actively publish research on energy technologies in the United States, and (3) congressional policy advisors and find that beliefs about global warming vary markedly among them. Scientists and policy advisors are more likely than the public to express a belief in the existence and anthropogenic nature of global warming. We also find ideological polarization about global warming in all three groups, although scientists are less polarized than the public and policy advisors over whether global warming is actually occurring. Alarmingly, there is evidence that the ideological divide about global warming gets significantly larger according to respondents’ knowledge about politics, energy, and science.
---------------------
Arctic warming will promote Atlantic–Pacific fish interchange
M.S. Wisz et al.
Nature Climate Change, March 2015, Pages 261–265
Abstract:
Throughout much of the Quaternary Period, inhospitable environmental conditions above the Arctic Circle have been a formidable barrier separating most marine organisms in the North Atlantic from those in the North Pacific. Rapid warming has begun to lift this barrier, potentially facilitating the interchange of marine biota between the two seas. Here, we forecast the potential northward progression of 515 fish species following climate change, and report the rate of potential species interchange between the Atlantic and the Pacific via the Northwest Passage and the Northeast Passage. For this, we projected niche-based models under climate change scenarios and simulated the spread of species through the passages when climatic conditions became suitable. Results reveal a complex range of responses during this century, and accelerated interchange after 2050. By 2100 up to 41 species could enter the Pacific and 44 species could enter the Atlantic, via one or both passages. Consistent with historical and recent biodiversity interchanges, this exchange of fish species may trigger changes for biodiversity and food webs in the North Atlantic and North Pacific, with ecological and economic consequences to ecosystems that at present contribute 39% to global marine fish landings.
---------------------
The fingerprint of climate trends on European crop yields
Frances Moore & David Lobell
Proceedings of the National Academy of Sciences, 3 March 2015, Pages 2670–2675
Abstract:
Europe has experienced a stagnation of some crop yields since the early 1990s as well as statistically significant warming during the growing season. Although it has been argued that these two are causally connected, no previous studies have formally attributed long-term yield trends to a changing climate. Here, we present two statistical tests based on the distinctive spatial pattern of climate change impacts and adaptation, and explore their power under a range of parameter values. We show that statistical power for the identification of climate change impacts is high in many settings, but that power for identifying adaptation is almost always low. Applying these tests to European agriculture, we find evidence that long-term temperature and precipitation trends since 1989 have reduced continent-wide wheat and barley yields by 2.5% and 3.8%, respectively, and have slightly increased maize and sugar beet yields. These averages disguise large heterogeneity across the continent, with regions around the Mediterranean experiencing significant adverse impacts on most crops. This result means that climate trends can account for ∼10% of the stagnation in European wheat and barley yields, with likely explanations for the remainder including changes in agriculture and environmental policies.