Follow the energy
Do alternative energy sources displace fossil fuels?
Richard York
Nature Climate Change, forthcoming
Abstract:
A fundamental, generally implicit, assumption of the Intergovernmental Panel on Climate Change reports and many energy analysts is that each unit of energy supplied by non-fossil-fuel sources takes the place of a unit of energy supplied by fossil-fuel sources. However, owing to the complexity of economic systems and human behaviour, it is often the case that changes aimed at reducing one type of resource consumption, either through improvements in efficiency of use or by developing substitutes, do not lead to the intended outcome when net effects are considered. Here, I show that the average pattern across most nations of the world over the past fifty years is one where each unit of total national energy use from non-fossil-fuel sources displaced less than one-quarter of a unit of fossil-fuel energy use and, focusing specifically on electricity, each unit of electricity generated by non-fossil-fuel sources displaced less than one-tenth of a unit of fossil-fuel-generated electricity. These results challenge conventional thinking in that they indicate that suppressing the use of fossil fuel will require changes other than simply technical ones such as expanding non-fossil-fuel energy production.
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Declining public concern about climate change: Can we blame the great recession?
Lyle Scruggs & Salil Benegal
Global Environmental Change, forthcoming
Abstract:
Social surveys suggest that the American public's concern about climate change has declined dramatically since 2008. This has led to a search for explanations for this decline, and great deal of speculation that there has been a fundamental shift in public trust in climate science. We evaluate over thirty years of public opinion data about global warming and the environment, and suggest that the decline in belief about climate change is most likely driven by the economic insecurity caused by the Great Recession. Evidence from European nations further supports an economic explanation for changing public opinion. The pattern is consistent with more than forty years of public opinion about environmental policy. Popular alternative explanations for declining support - partisan politicization, biased media coverage, fluctuations in short-term weather conditions - are unable to explain the suddenness and timing of opinion trends. The implication of these findings is that the "crisis of confidence" in climate change will likely rebound after labor market conditions improve, but not until then.
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Observed decreases in the Canadian outdoor skating season due to recent winter warming
Nikolay Damyanov, Damon Matthews & Lawrence Mysak
Environmental Research Letters, January-March 2012
Abstract:
Global warming has the potential to negatively affect one of Canada's primary sources of winter recreation: hockey and ice skating on outdoor rinks. Observed changes in winter temperatures in Canada suggest changes in the meteorological conditions required to support the creation and maintenance of outdoor skating rinks; while there have been observed increases in the ice-free period of several natural water bodies, there has been no study of potential trends in the duration of the season supporting the construction of outdoor skating rinks. Here we show that the outdoor skating season (OSS) in Canada has significantly shortened in many regions of the country as a result of changing climate conditions. We first established a meteorological criterion for the beginning, and a proxy for the length of the OSS. We extracted this information from daily maximum temperature observations from 1951 to 2005, and tested it for significant changes over time due to global warming as well as due to changes in patterns of large-scale natural climate variability. We found that many locations have seen a statistically significant decrease in the OSS length, particularly in Southwest and Central Canada. This suggests that future global warming has the potential to significantly compromise the viability of outdoor skating in Canada.
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Lifetime of carbon capture and storage as a climate-change mitigation technology
Michael Szulczewski et al.
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
In carbon capture and storage (CCS), CO2 is captured at power plants and then injected underground into reservoirs like deep saline aquifers for long-term storage. While CCS may be critical for the continued use of fossil fuels in a carbon-constrained world, the deployment of CCS has been hindered by uncertainty in geologic storage capacities and sustainable injection rates, which has contributed to the absence of concerted government policy. Here, we clarify the potential of CCS to mitigate emissions in the United States by developing a storage-capacity supply curve that, unlike current large-scale capacity estimates, is derived from the fluid mechanics of CO2 injection and trapping and incorporates injection-rate constraints. We show that storage supply is a dynamic quantity that grows with the duration of CCS, and we interpret the lifetime of CCS as the time for which the storage supply curve exceeds the storage demand curve from CO2 production. We show that in the United States, if CO2 production from power generation continues to rise at recent rates, then CCS can store enough CO2 to stabilize emissions at current levels for at least 100 y. This result suggests that the large-scale implementation of CCS is a geologically viable climate-change mitigation option in the United States over the next century.
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Is it possible to limit global warming to no more than 1.5°C?
N. Ranger et al.
Climatic Change, April 2012, Pages 973-981
Abstract:
This study explores the feasibility of limiting increases in global temperature to 1.5°C above pre-industrial levels. A probabilistic simple climate model is used to identify emissions paths that offer at least a 50% chance of achieving this goal. We conclude that it is more likely than not that warming would exceed 1.5°C, at least temporarily, under plausible mitigation scenarios. We have identified three criteria of emissions paths that could meet the 1.5°C goal with a temporary overshoot of no more than 50 years: early and strong reductions in emissions, with global emissions peaking in 2015 and falling to at most 44-48 GtCO2e in 2020; rapid reductions in annual global emissions after 2020 (of at least 3-4% per year); very low annual global emissions by 2100 (less than 2-4 GtCO2e) and falling to zero (or below) in the 22nd century. The feasibility of these characteristics is uncertain. We conclude that the proposed date of review of the 1.5°C goal, set at 2015, may be too late to achieve the necessary scaling up of emissions cuts to achieve this goal.
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Economic development and carbon dioxide emissions in China: Provincial panel data analysis
Limin Du, Chu Wei & Shenghua Cai
China Economic Review, forthcoming
Abstract:
This paper investigates the driving forces, emission trends and reduction potential of China's carbon dioxide (CO2) emissions based on a provincial panel data set covering the years 1995 to 2009. A series of static and dynamic panel data models are estimated, and then an optimal forecasting model selected by out-of-sample criteria is used to forecast the emission trend and reduction potential up to 2020. The estimation results show that economic development, technology progress and industry structure are the most important factors affecting China's CO2 emissions, while the impacts of energy consumption structure, trade openness and urbanization level are negligible. The inverted U-shaped relationship between per capita CO2 emissions and economic development level is not strongly supported by the estimation results. The impact of capital adjustment speed is significant. Scenario simulations further show that per capita and aggregate CO2 emissions of China will increase continuously up to 2020 under any of the three scenarios developed in this study, but the reduction potential is large.
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The impact of climate change on global tropical cyclone damage
Robert Mendelsohn et al.
Nature Climate Change, March 2012, Pages 205-209
Abstract:
One potential impact from greenhouse-gas emissions is increasing damage from extreme events. Here, we quantify how climate change may affect tropical cyclone damage. We find that future increases in income are likely to double tropical cyclone damage even without climate change. Climate change is predicted to increase the frequency of high-intensity storms in selected ocean basins depending on the climate model. Climate change doubles economic damage, but the result depends on the parameters of the damage function. Almost all of the tropical cyclone damage from climate change tends to be concentrated in North America, East Asia and the Caribbean-Central American region. This paper provides a framework to combine atmospheric science and economics, but some effects are not yet modelled, including sea-level rise and adaptation.
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Makena Coffman & Ilan Noy
Environment and Development Economics, April 2012, Pages 187-205
Abstract:
The long-term impacts of disasters are ‘hidden' as it becomes increasingly difficult over time to attribute them to a singular event. We use a synthetic control methodology, formalized in Abadie, A. et al. (2010), Synthetic control methods for comparative case studies: estimating the effect of California's tobacco control program, Journal of the American Statistical Association 105(490): 493-505, to estimate the long-term impacts of a 1992 hurricane on the Hawaiian island of Kauai. Hurricane Iniki, the strongest storm to hit Hawaii in many years, wrought an estimated US$ 7.4 billion (2008) in direct damages. Since the unaffected Hawaiian Islands provide a control group, the case of Iniki is uniquely suited to provide insight into the long-term impact of natural disasters. We show that Kauai's economy has yet to recover, 18 years after this event. We estimate the island's current population to be 12 per cent smaller than it would have been had the hurricane not occurred. Similarly, aggregate personal income and the number of private sector jobs are proportionally lower.
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Impact of declining Arctic sea ice on winter snowfall
Jiping Liu et al.
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
While the Arctic region has been warming strongly in recent decades, anomalously large snowfall in recent winters has affected large parts of North America, Europe, and east Asia. Here we demonstrate that the decrease in autumn Arctic sea ice area is linked to changes in the winter Northern Hemisphere atmospheric circulation that have some resemblance to the negative phase of the winter Arctic oscillation. However, the atmospheric circulation change linked to the reduction of sea ice shows much broader meridional meanders in midlatitudes and clearly different interannual variability than the classical Arctic oscillation. This circulation change results in more frequent episodes of blocking patterns that lead to increased cold surges over large parts of northern continents. Moreover, the increase in atmospheric water vapor content in the Arctic region during late autumn and winter driven locally by the reduction of sea ice provides enhanced moisture sources, supporting increased heavy snowfall in Europe during early winter and the northeastern and midwestern United States during winter. We conclude that the recent decline of Arctic sea ice has played a critical role in recent cold and snowy winters.
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Wind Turbines Make Waves: Why Some Residents Near Wind Turbines Become Ill
Magda Havas & David Colling
Bulletin of Science, Technology & Society, October 2011, Pages 414-426
Abstract:
People who live near wind turbines complain of symptoms that include some combination of the following: difficulty sleeping, fatigue, depression, irritability, aggressiveness, cognitive dysfunction, chest pain/pressure, headaches, joint pain, skin irritations, nausea, dizziness, tinnitus, and stress. These symptoms have been attributed to the pressure (sound) waves that wind turbines generate in the form of noise and infrasound. However, wind turbines also generate electromagnetic waves in the form of poor power quality (dirty electricity) and ground current, and these can adversely affect those who are electrically hypersensitive. Indeed, the symptoms mentioned above are consistent with electrohypersensitivity. Sensitivity to both sound and electromagnetic waves differs among individuals and may explain why not everyone in the same home experiences similar effects. Ways to mitigate the adverse health effects of wind turbines are presented.
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Building vintage and electricity use: Old homes use less electricity in hot weather
Howard Chong
European Economic Review, forthcoming
Abstract:
This paper studies whether electricity use in newer or older residential buildings rises more in response to high temperature in a region of Southern California. Peak electricity demand occurs at the highest temperatures which are predicted to increase due to climate change. Understanding how newer buildings differ from older buildings improves forecasts of how peak electricity use will grow over time. Newer buildings are subject to stricter building energy codes, but are larger and more likely to have air conditioning; hence, the cumulative effect is ambiguous. This paper combines four large datasets of building and household characteristics, weather data, and utility data to estimate the electricity-temperature response of different building vintages. Estimation results show that new buildings (1970-2000) have a statistically significantly higher temperature response (i.e., use more electricity) than old buildings (pre-1970). Auxiliary regressions with controls for tiered electricity prices, number of bedrooms, income, square footage, central air conditioning, ownership, and type of residential structure partially decompose the effect. Though California has had extensive energy efficiency building standards that by themselves would lower temperature response for new buildings, the cumulative effect of new buildings is an increase in temperature response. As new buildings are added, aggregate temperature response is predicted to increase.
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Collapse of Classic Maya Civilization Related to Modest Reduction in Precipitation
Martín Medina-Elizalde & Eelco Rohling
Science, 24 February 2012, Pages 956-959
Abstract:
The disintegration of the Classic Maya civilization in the Yucatán Peninsula and Central America was a complex process that occurred over an approximately 200-year interval and involved a catastrophic depopulation of the region. Although it is well established that the civilization collapse coincided with widespread episodes of drought, their nature and severity remain enigmatic. We present a quantitative analysis that offers a coherent interpretation of four of the most detailed paleoclimate records of the event. We conclude that the droughts occurring during the disintegration of the Maya civilization represented up to a 40% reduction in annual precipitation, probably due to a reduction in summer season tropical storm frequency and intensity.
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Sea-Level Rise and Storm Surges: High Stakes for a Small Number of Developing Countries
Henrike Brecht et al.
Journal of Environment & Development, March 2012, Pages 120-138
Abstract:
As the climate changes during the 21st century, larger cyclonic storm surges and growing populations may collide in disasters of unprecedented size. As conditions worsen, variations in coastal morphology will magnify the effects in some areas, while largely insulating others. In this article, we explore the implications for 31 developing countries and 393 of their cyclone-vulnerable coastal cities with populations greater than 100,000. Combining the most recent scientific and demographic information, we estimate the future impact of climate change on storm surges that will strike coastal populations, economies, and ecosystems. We focus on the distribution of heightened impacts, because we believe that greater knowledge of their probable variation will be useful for local and national planners, as well as international donors. Our results suggest gross inequality in the heightened impact of future disasters, with 50% of the burden falling on the residents of 10 Asian cities and over 40% falling on Manila, Karachi, and Jakarta alone. In light of these huge asymmetries, we believe that careful targeting of international assistance will be essential for the effective and equitable allocation of resources for coastal protection and disaster prevention.
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Xi Lu, Jackson Salovaara & Michael McElroy
Environmental Science & Technology, 6 March 2012, Pages 3014-3021
Abstract:
CO2 emissions from the US power sector decreased by 8.76% in 2009 relative to 2008 contributing to a decrease over this period of 6.59% in overall US emissions of greenhouse gases. An econometric model, tuned to data reported for regional generation of US electricity, is used to diagnose factors responsible for the 2009 decrease. More than half of the reduction is attributed to a shift from generation of power using coal to gas driven by a recent decrease in gas prices in response to the increase in production from shale. An important result of the model is that, when the cost differential for generation using gas rather than coal falls below 2-3 cents/kWh, less efficient coal fired plants are displaced by more efficient natural gas combined cycle (NGCC) generation alternatives. Costs for generation using NGCC decreased by close to 4 cents/kWh in 2009 relative to 2008 ensuring that generation of electricity using gas was competitive with coal in 2009 in contrast to the situation in 2008 when gas prices were much higher. A modest price on carbon could contribute to additional switching from coal to gas with further savings in CO2 emissions.
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Arlene Rosen & Isabel Rivera-Collazo
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
Climatic forcing during the Younger Dryas (∼12.9-11.5 ky B.P.) event has become the theoretical basis to explain the origins of agricultural lifestyles in the Levant by suggesting a failure of foraging societies to adjust. This explanation however, does not fit the scarcity of data for predomestication cultivation in the Natufian Period. The resilience of Younger Dryas foragers is better illustrated by a concept of adaptive cycles within a theory of adaptive change (resilience theory). Such cycles consist of four phases: release/collapse (Ω); reorganization (α), when the system restructures itself after a catastrophic stimulus through innovation and social memory - a period of greater resilience and less vulnerability; exploitation (r); and conservation (K), representing an increasingly rigid system that loses flexibility to change. The Kebarans and Late Natufians had similar responses to cold and dry conditions vs. Early Natufians and the Pre-Pottery Neolithic A responses to warm and wet climates. Kebarans and Late Natufians (α-phase) shifted to a broader-based diet and increased their mobility. Early Natufian and Pre-Pottery Neolithic A populations (r- and K-phases) had a growing investment in more narrowly focused, high-yield plant resources, but they maintained the broad range of hunted animals because of increased sedentism. These human adaptive cycles interlocked with plant and animal cycles. Forest and grassland vegetation responded to late Pleistocene and early Holocene climatic fluctuations, but prey animal cycles reflected the impact of human hunting pressure. The combination of these three adaptive cycles results in a model of human adaptation, showing potential for great sustainability of Levantine foraging systems even under adverse climatic conditions.
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Understanding the Solar Home Price Premium: Electricity Generation and "Green" Social Status
Samuel Dastrup et al.
European Economic Review, forthcoming
Abstract:
This study uses a large sample of homes in the San Diego area and Sacramento, California area to provide some of the first capitalization estimates of the sales value of homes with solar panels relative to comparable homes without solar panels. Although the residential solar home market continues to grow, there is little direct evidence on the market capitalization effect. Using both hedonics and a repeat sales index approach we find that solar panels are capitalized at roughly a 3.5% premium. This premium is larger in communities with a greater share of college graduates and of registered Prius hybrid vehicles.
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Detecting regional anthropogenic trends in ocean acidification against natural variability
T. Friedrich et al.
Nature Climate Change, March 2012, Pages 167-171
Abstract:
Since the beginning of the Industrial Revolution humans have released ~500 billion metric tons of carbon to the atmosphere through fossil-fuel burning, cement production and land-use changes. About 30% has been taken up by the oceans. The oceanic uptake of carbon dioxide leads to changes in marine carbonate chemistry resulting in a decrease of seawater pH and carbonate ion concentration, commonly referred to as ocean acidification. Ocean acidification is considered a major threat to calcifying organisms. Detecting its magnitude and impacts on regional scales requires accurate knowledge of the level of natural variability of surface ocean carbonate ion concentrations on seasonal to annual timescales and beyond. Ocean observations are severely limited with respect to providing reliable estimates of the signal-to-noise ratio of human-induced trends in carbonate chemistry against natural factors. Using three Earth system models we show that the current anthropogenic trend in ocean acidification already exceeds the level of natural variability by up to 30 times on regional scales. Furthermore, it is demonstrated that the current rates of ocean acidification at monitoring sites in the Atlantic and Pacific oceans exceed those experienced during the last glacial termination by two orders of magnitude.
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Innovation under cap-and-trade programs
Margaret Taylor
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
Policies incentivizing the private sector to reach its innovative potential in "clean" technologies are likely to play a key role in achieving climate stabilization. This article explores the relationship between innovation and cap-and-trade programs (CTPs) - the world's most prominent climate policy instrument - through empirical evidence drawn from successful CTPs for sulfur dioxide and nitrogen oxide control. The article shows that before trading began for these CTPs, analysts overestimated the value of allowances in a pattern suggestive of the frequent a priori overestimation of the compliance costs of regulation. When lower-than-expected allowance prices were observed, in part because of the unexpected range of abatement approaches used in the lead-up to trading, emissions sources chose to bank allowances in significant numbers and reassess abatement approaches going forward. In addition, commercially oriented inventive activity declined for emissions-reducing technologies with a wide range of costs and technical characteristics, dropping from peaks before the establishment of CTPs to nadirs a few years into trading. This finding is consistent with innovators deciding during trading that their research and development investments should be reduced, based on assessments of future market conditions under the relevant CTPs. The article concludes with a discussion of the results and their implications for innovation and climate policy.
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Modelling sea level rise impacts on storm surges along US coasts
Claudia Tebaldi, Benjamin Strauss & Chris Zervas
Environmental Research Letters, January-March 2012
Abstract:
Sound policies for protecting coastal communities and assets require good information about vulnerability to flooding. Here, we investigate the influence of sea level rise on expected storm surge-driven water levels and their frequencies along the contiguous United States. We use model output for global temperature changes, a semi-empirical model of global sea level rise, and long-term records from 55 nationally distributed tidal gauges to develop sea level rise projections at each gauge location. We employ more detailed records over the period 1979-2008 from the same gauges to elicit historic patterns of extreme high water events, and combine these statistics with anticipated relative sea level rise to project changing local extremes through 2050. We find that substantial changes in the frequency of what are now considered extreme water levels may occur even at locations with relatively slow local sea level rise, when the difference in height between presently common and rare water levels is small. We estimate that, by mid-century, some locations may experience high water levels annually that would qualify today as 'century' (i.e., having a chance of occurrence of 1% annually) extremes. Today's century levels become 'decade' (having a chance of 10% annually) or more frequent events at about a third of the study gauges, and the majority of locations see substantially higher frequency of previously rare storm-driven water heights in the future. These results add support to the need for policy approaches that consider the non-stationarity of extreme events when evaluating risks of adverse climate impacts.
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Mansour Almazroui et al.
International Journal of Climatology, forthcoming
Abstract:
The rainfall and temperature climatology over the Arabian Peninsula are analysed on an annual basis using various gridded datasets. For Saudi Arabia, the area of which represents almost 80% of the Peninsula, the climatic datasets from its 27 ground observations are analysed for the period 1978-2009, with additional gridded datasets used to describe the observed state and change of the present climate. The gridded datasets represent well the very dry (40-80 mm) area over the world's largest sand desert (Rub Al-Khali), the dry (80-150 mm) area over middle-to-north of Saudi Arabia, and the wettest (>150 mm) region in the southwest of the Peninsula. The annual temperature is relatively high (24-27 °C) in the middle-to-south of the Peninsula and low (<21 °C) in the northwest and southwest. The highest temperature (>27 °C) is obtained over the Rub Al-Khali. Over Saudi Arabia, the observed annual rainfall showed a significant decreasing trend (47.8 mm per decade) in the last half of the analysis period, with a relatively large interannual variability, while the maximum, mean and minimum temperatures have increased significantly at a rate of 0.71, 0.60, and 0.48 °C per decade, respectively. This information is invaluable to consider in any climate impact assessment studies in Saudi Arabia.
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The Geological Record of Ocean Acidification
Bärbel Hönisch et al.
Science, 2 March 2012, Pages 1058-1063
Abstract:
Ocean acidification may have severe consequences for marine ecosystems; however, assessing its future impact is difficult because laboratory experiments and field observations are limited by their reduced ecologic complexity and sample period, respectively. In contrast, the geological record contains long-term evidence for a variety of global environmental perturbations, including ocean acidification plus their associated biotic responses. We review events exhibiting evidence for elevated atmospheric CO2, global warming, and ocean acidification over the past ~300 million years of Earth's history, some with contemporaneous extinction or evolutionary turnover among marine calcifiers. Although similarities exist, no past event perfectly parallels future projections in terms of disrupting the balance of ocean carbonate chemistry - a consequence of the unprecedented rapidity of CO2 release currently taking place.
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Long-term perspective on wildfires in the western USA
Jennifer Marlon et al.
Proceedings of the National Academy of Sciences, 28 February 2012, Pages E535-E543
Abstract:
Understanding the causes and consequences of wildfires in forests of the western United States requires integrated information about fire, climate changes, and human activity on multiple temporal scales. We use sedimentary charcoal accumulation rates to construct long-term variations in fire during the past 3,000 y in the American West and compare this record to independent fire-history data from historical records and fire scars. There has been a slight decline in burning over the past 3,000 y, with the lowest levels attained during the 20th century and during the Little Ice Age (LIA, ca. 1400-1700 CE [Common Era]). Prominent peaks in forest fires occurred during the Medieval Climate Anomaly (ca. 950-1250 CE) and during the 1800s. Analysis of climate reconstructions beginning from 500 CE and population data show that temperature and drought predict changes in biomass burning up to the late 1800s CE. Since the late 1800s , human activities and the ecological effects of recent high fire activity caused a large, abrupt decline in burning similar to the LIA fire decline. Consequently, there is now a forest "fire deficit" in the western United States attributable to the combined effects of human activities, ecological, and climate changes. Large fires in the late 20th and 21st century fires have begun to address the fire deficit, but it is continuing to grow.
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Examining barriers and opportunities for sustainable adaptation to climate change in Interior Alaska
Shannon McNeeley
Climatic Change, April 2012, Pages 835-857
Abstract:
Human adaptation to climate change is comprised of "adjustments" in response to (or anticipation of) climatic impacts. Adaptation does not necessarily imply favorable or equitable change, nor does it automatically imply sustainable use of ecosystems. "Sustainable adaptation" in this case implies strategic, collective action to respond to or anticipate harmful climate change to reduce disruption to key resource flows and adverse effects on general well-being. This research examined social-ecological system responses to recent warming trends in the remote northwest region of Interior Alaska using a unique vulnerability and adaptive capacity assessment (VA) approach that integrated indigenous observations and understanding of climate (IC) with western social and natural sciences. The study found that Alaska Native communities that were historically highly mobile and flexible across the landscape for subsistence hunting are increasingly restricted by the institutional rigidity of the regulatory system for wildlife and subsistence management. This has resulted in negative impacts to game harvest access and success threatening food security and community well-being. This suggests that policies limiting the ability of natural resource-dependent societies to be flexible, diversify, or innovate can threaten livelihoods and exacerbate vulnerability. Nevertheless, opportunities for sustainable adaptation exist where wildlife management is adaptive and includes an understanding of and response to climate variability and slow-onset climate change with the human dimensions of subsistence hunting for more effective "in-season" management.
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Multistability and critical thresholds of the Greenland ice sheet
Alexander Robinson, Reinhard Calov & Andrey Ganopolski
Nature Climate Change, forthcoming
Abstract:
Recent studies have focused on the short-term contribution of the Greenland ice sheet to sea-level rise, yet little is known about its long-term stability. The present best estimate of the threshold in global temperature rise leading to complete melting of the ice sheet is 3.1 °C (1.9-5.1 °C, 95% confidence interval) above the preindustrial climate1, determined as the temperature for which the modelled surface mass balance of the present-day ice sheet turns negative. Here, using a fully coupled model, we show that this criterion systematically overestimates the temperature threshold and that the Greenland ice sheet is more sensitive to long-term climate change than previously thought. We estimate that the warming threshold leading to a monostable, essentially ice-free state is in the range of 0.8-3.2 °C, with a best estimate of 1.6 °C. By testing the ice sheet's ability to regrow after partial mass loss, we find that at least one intermediate equilibrium state is possible, though for sufficiently high initial temperature anomalies, total loss of the ice sheet becomes irreversible. Crossing the threshold alone does not imply rapid melting (for temperatures near the threshold, complete melting takes tens of millennia). However, the timescale of melt depends strongly on the magnitude and duration of the temperature overshoot above this critical threshold.
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High tide of the warm Pliocene: Implications of global sea level for Antarctic deglaciation
Kenneth Miller et al.
Geology, forthcoming
Abstract:
We obtained global sea-level (eustatic) estimates with a peak of ∼22 m higher than present for the Pliocene interval 2.7-3.2 Ma from backstripping in Virginia (United States), New Zealand, and Enewetak Atoll (north Pacific Ocean), benthic foraminiferal δ18O values, and Mg/Ca-δ18O estimates. Statistical analysis indicates that it is likely (68% confidence interval) that peak sea level was 22 ± 5 m higher than modern, and extremely likely (95%) that it was 22 ± 10 m higher than modern. Benthic foraminiferal δ18O values appear to require that the peak was <20-21 m. Our estimates imply loss of the equivalent of the Greenland and West Antarctic ice sheets, and some volume loss from the East Antarctic Ice Sheet, and address the long-standing controversy concerning the Pliocene stability of the East Antarctic Ice Sheet.