Up in the air
Dana Fisher, Joseph Waggle & Philip Leifeld
American Behavioral Scientist, January 2013, Pages 70-92
Abstract:
How do we understand political polarization within the U.S. climate change debate? This article unpacks the different components of the debate to determine the source of the political divide that is so noted in the mainstream media and academic literatures. Through analysis of the content of congressional hearings on the issue of climate change, we are able to explain political polarization of the issue more fully. In particular, our results show that, contrary to representations in the mainstream media, there is increasing consensus over the science of the issue. Discussions of the type of policy instrument and the economic implications of regulating carbon dioxide emissions, however, continue to polarize opinion. This article concludes by exploring how these findings help us understand more recent political events around climate change.
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Little change in global drought over the past 60 years
Justin Sheffield, Eric Wood & Michael Roderick
Nature, 15 November 2012, Pages 435-438
Abstract:
Drought is expected to increase in frequency and severity in the future as a result of climate change, mainly as a consequence of decreases in regional precipitation but also because of increasing evaporation driven by global warming. Previous assessments of historic changes in drought over the late twentieth and early twenty-first centuries indicate that this may already be happening globally. In particular, calculations of the Palmer Drought Severity Index (PDSI) show a decrease in moisture globally since the 1970s with a commensurate increase in the area in drought that is attributed, in part, to global warming. The simplicity of the PDSI, which is calculated from a simple water-balance model forced by monthly precipitation and temperature data, makes it an attractive tool in large-scale drought assessments, but may give biased results in the context of climate change. Here we show that the previously reported increase in global drought is overestimated because the PDSI uses a simplified model of potential evaporation that responds only to changes in temperature and thus responds incorrectly to global warming in recent decades. More realistic calculations, based on the underlying physical principles that take into account changes in available energy, humidity and wind speed, suggest that there has been little change in drought over the past 60 years. The results have implications for how we interpret the impact of global warming on the hydrological cycle and its extremes, and may help to explain why palaeoclimate drought reconstructions based on tree-ring data diverge from the PDSI-based drought record in recent years.
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Sammy Zahran, Daniele Tavani & Stephan Weiler
Risk Analysis, forthcoming
Abstract:
Casualties from natural disasters may depend on the day of the week they strike. With data from the Spatial Hazard Events and Losses Database for the United States (SHELDUS), daily variation in hurricane and tornado casualties from 5,043 tornado and 2,455 hurricane time/place events is analyzed. Hurricane forecasts provide at-risk populations with considerable lead time. Such lead time allows strategic behavior in choosing protective measures under hurricane threat; opportunity costs in terms of lost income are higher during weekdays than during weekends. On the other hand, the lead time provided by tornadoes is near zero; hence tornados generate no opportunity costs. Tornado casualties are related to risk information flows, which are higher during workdays than during leisure periods, and are related to sheltering-in-place opportunities, which are better in permanent buildings like businesses and schools. Consistent with theoretical expectations, random effects negative binomial regression results indicate that tornado events occurring on the workdays of Monday through Thursday are significantly less lethal than tornados that occur on weekends. In direct contrast, and also consistent with theory, the expected count of hurricane casualties increases significantly with weekday occurrences. The policy implications of observed daily variation in tornado and hurricane events are considered.
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Drawing attention to global climate change decreases support for war
Tom Pyszczynski et al.
Peace and Conflict: Journal of Peace Psychology, November 2012, Pages 354-368
Abstract:
Three studies showed that focus on the shared human threat of global climate change can encourage peaceful coexistence and discourage support for war in the face of existential threat. In Study 1, mortality salience (MS) increased Americans' support for international peace-building after imagining the consequences of global climate change, but not after imagining a localized catastrophe. Conversely, in Study 2, MS increased Americans' support for war against Iran after imagining a localized catastrophe, but imagining global climate change completely eliminated this effect. Study 3 was conducted among Arab citizens of Israel during the January 2009 Israeli invasion of Gaza. For those high in perceptions of shared humanity, MS increased support for peaceful coexistence with Israeli Jews after imagining global climate change but not a localized catastrophe that would affect both Muslims and Jews. Taken together, these studies suggest that reminders of global climate change short-circuit the increased support for violence that often occurs in response to existential threat and increase support for peaceful reconciliation.
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Homogeneous record of Atlantic hurricane surge threat since 1923
Aslak Grinsted, John Moore & Svetlana Jevrejeva
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
Detection and attribution of past changes in cyclone activity are hampered by biased cyclone records due to changes in observational capabilities. Here we construct an independent record of Atlantic tropical cyclone activity on the basis of storm surge statistics from tide gauges. We demonstrate that the major events in our surge index record can be attributed to landfalling tropical cyclones; these events also correspond with the most economically damaging Atlantic cyclones. We find that warm years in general were more active in all cyclone size ranges than cold years. The largest cyclones are most affected by warmer conditions and we detect a statistically significant trend in the frequency of large surge events (roughly corresponding to tropical storm size) since 1923. In particular, we estimate that Katrina-magnitude events have been twice as frequent in warm years compared with cold years (P < 0.02).
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A Cooling Climate for Change? Party Polarization and the Politics of Global Warming
Deborah Lynn Guber
American Behavioral Scientist, January 2013, Pages 93-115
Abstract:
Analysis of three cross-sectional polls administered by the Gallup Organization at 10-year intervals - in 1990, 2000, and 2010 - demonstrates that partisan identification has become an increasingly important determinant of environmental concern within the American mass public. Polarization on global warming is especially clear, even when compared to a variety of other social, economic, and political problems, but party sorting seems to occur only as citizens acquire information and become familiar with elite cues. The implications of this for the U.S. environmental movement and the strategies it employs are discussed.
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How does climate change cause extinction?
Abigail Cahill et al.
Proceedings of the Royal Society: Biological Sciences, 7 January 2013
Abstract:
Anthropogenic climate change is predicted to be a major cause of species extinctions in the next 100 years. But what will actually cause these extinctions? For example, will it be limited physiological tolerance to high temperatures, changing biotic interactions or other factors? Here, we systematically review the proximate causes of climate-change related extinctions and their empirical support. We find 136 case studies of climatic impacts that are potentially relevant to this topic. However, only seven identified proximate causes of demonstrated local extinctions due to anthropogenic climate change. Among these seven studies, the proximate causes vary widely. Surprisingly, none show a straightforward relationship between local extinction and limited tolerances to high temperature. Instead, many studies implicate species interactions as an important proximate cause, especially decreases in food availability. We find very similar patterns in studies showing decreases in abundance associated with climate change, and in those studies showing impacts of climatic oscillations. Collectively, these results highlight our disturbingly limited knowledge of this crucial issue but also support the idea that changing species interactions are an important cause of documented population declines and extinctions related to climate change. Finally, we briefly outline general research strategies for identifying these proximate causes in future studies.
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Jun Wang et al.
Climatic Change, December 2012, Pages 537-558
Abstract:
Shanghai is a low-lying city (3-4 m elevation) surrounded on three sides by the East China Sea, the Yangtze River Estuary, and Hangzhou Bay. With a history of rapid changes in sea level and land subsidence, Shanghai is often plagued by extreme typhoon storm surges. The interaction of sea level rise, land subsidence, and storm surges may lead to more complex, variable, and abrupt disasters. In this paper, we used MIKE 21 models to simulate the combined effect of this disaster chain in Shanghai. Projections indicate that the sea level will rise 86.6 mm, 185.6 mm, and 433.1 mm by 2030, 2050, and 2100, respectively. Anthropogenic subsidence is a serious problem. The maximum annual subsidence rate is 24.12 mm/year. By 2100, half of Shanghai is projected to be flooded, and 46 % of the seawalls and levees are projected to be overtopped. The risk of flooding is closely related to the impact of land subsidence on the height of existing seawalls and levees. Land subsidence increases the need for flood control measures in Shanghai.
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Market-Based Responses to Climate Change: CO2 Market Design versus Operation
Gareth Veal & Stefanos Mouzas
Organization Studies, November 2012, Pages 1589-1616
Abstract:
This study highlights significant discrepancies between CO2 market design and the actual operation of CO2 markets. Our findings are based upon an empirical investigation undertaken in the context of the European Emissions Trading Scheme between January 2009 and May 2010. CO2 markets are examined from a practice-based perspective in which actors are engaged in exchange, representational and normalizing practices. Discrepancies between the actual and intended CO2 market practices are explained using the concepts of framing, overflowing and regulatory capture. We argue that the design of the European Emissions Trading Scheme has been influenced in such a way that it does not actually challenge market participants to reduce their CO2 emissions. In this way, the study challenges the near universal reliance upon CO2 markets as the primary policy mechanism for mitigating climate change.
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The relationship between temperature and CO2 emissions: Evidence from a short and very long dataset
David McMillan & Mark Wohar
Applied Economics, October 2012, Pages 3683-3690
Abstract:
The debate regarding rising temperatures and CO2 emissions has attracted the attention of economists employing recent econometric techniques. This article extends the previous literature using a dataset that covers 800 000 years, as well as a shorter dataset, and examines the interaction between temperature and CO2 emissions. Unit root tests reveal a difference between the two datasets. For the long dataset, all tests support the view that both temperature and CO2 are stationary around a constant. For the short dataset, temperature exhibits trend-stationary behaviour, while CO2 contains a unit root. This result is robust to nonlinear trends or trend breaks. Modelling the long dataset reveals that while contemporaneous CO2 appears positive and significant in the temperature equation, including lags results in a joint effect that is near zero. This result is confirmed using a different lag structure and Vector Autoregressive (VAR) model. A Generalized Method of Moments (GMM) approach to account for endogeneity suggests an insignificant relationship. In sum, the key result from our analysis is that CO2 has, at best, a weak relationship with temperature, while there is no evidence of trending when using a sufficiently long dataset. Thus, as a secondary result we highlight the danger of using a small sample in this context.
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The effects of rerouting aircraft around the arctic circle on arctic and global climate
Mark Jacobson et al.
Climatic Change, December 2012, Pages 709-724
Abstract:
Climate data suggest greater warming over the Arctic than lower latitudes, and the most abundant direct source of black carbon and other climate-relevant pollutants over the Arctic is cross-polar flights by international aviation. A relevant question is whether rerouting cross-polar flights to circumnavigate the Arctic Circle reduces or enhances such warming. To study this issue, a model accounting for subgrid exhaust plumes from each individual commercial flight worldwide was used with 2006 global aircraft emission inventories that treated cross-polar flights and flights rerouted around the Arctic Circle (66.56083 °N), respectively. Rerouting increased fuel use by 0.056 % in the global average, mostly right outside the Arctic Circle, but most of the associated black carbon and other emissions were removed faster because they were now over latitudes of greater precipitation and lesser stability. Rerouting also reduced fuel use and emissions within the Arctic Circle by 83 % and delayed pollutant transport to the Arctic. The Arctic reduction in pollutants, particularly of black carbon, decreased Arctic and global temperature and increased Arctic sea ice over 22 years. Although the slight increase in total CO2 emissions due to rerouting may dampen the benefit of rerouting over more decades, rerouting or even partial rerouting (allowing cross-polar flights during polar night only) may delay the elimination of Arctic sea ice, which will otherwise likely occur within the next 2-3 decades due to global warming in general. Rerouting may increase worldwide fuel plus operational costs by only ~$99 million/yr, 47-55 times less than an estimated 2025 U.S.-alone cost savings due to the global warming reduction from rerouting.
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Parental environment mediates impacts of increased carbon dioxide on a coral reef fish
Gabrielle Miller et al.
Nature Climate Change, December 2012, Pages 858-861
Abstract:
Carbon dioxide concentrations in the surface ocean are increasing owing to rising CO2 concentrations in the atmosphere1. Higher CO2 levels are predicted to affect essential physiological processes of many aquatic organisms2, 3, leading to widespread impacts on marine diversity and ecosystem function, especially when combined with the effects of global warming4, 5, 6. Yet the ability for marine species to adjust to increasing CO2 levels over many generations is an unresolved issue. Here we show that ocean conditions projected for the end of the century (approximately 1,000 μatm CO2 and a temperature rise of 1.5-3.0 °C) cause an increase in metabolic rate and decreases in length, weight, condition and survival of juvenile fish. However, these effects are absent or reversed when parents also experience high CO2 concentrations. Our results show that non-genetic parental effects can dramatically alter the response of marine organisms to increasing CO2 and demonstrate that some species have more capacity to acclimate to ocean acidification than previously thought.
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Toward a physically plausible upper bound of sea-level rise projections
Ryan Sriver et al.
Climatic Change, December 2012, Pages 893-902
Abstract:
Anthropogenic sea-level rise (SLR) causes considerable risks. Designing a sound SLR risk-management strategy requires careful consideration of decision-relevant uncertainties such as the reasonable upper bound of future SLR. The recent Intergovernmental Panel on Climate Change's (IPCC) Fourth Assessment reported a likely upper SLR bound in the year 2100 near 0.6 m (meter). More recent studies considering semi-empirical modeling approaches and kinematic constraints on glacial melting suggest a reasonable 2100 SLR upper bound of approximately 2 m. These recent studies have broken important new ground, but they largely neglect uncertainties surrounding thermal expansion (thermosteric SLR) and/or observational constraints on ocean heat uptake. Here we quantify the effects of key parametric uncertainties and observational constraints on thermosteric SLR projections using an Earth system model with a dynamic three-dimensional ocean, which provides a mechanistic representation of deep ocean processes and heat uptake. Considering these effects nearly doubles the contribution of thermosteric SLR compared to previous estimates and increases the reasonable upper bound of 2100 SLR projections by 0.25 m. As an illustrative example of the effect of overconfidence, we show how neglecting thermosteric uncertainty in projections of the SLR upper bound can considerably bias risk analysis and hence the design of adaptation strategies. For conditions close to the Port of Los Angeles, the 0.25 m increase in the reasonable upper bound can result in a flooding-risk increase by roughly three orders of magnitude. Results provide evidence that relatively minor underestimation of the upper bound of projected SLR can lead to major downward biases of future flooding risks.
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Long-term sea-level rise implied by 1.5 °C and 2 °C warming levels
Michiel Schaeffer et al.
Nature Climate Change, December 2012, Pages 867-870
Abstract:
Sea-level rise (SLR) is a critical and uncertain climate change risk, involving timescales of centuries. Here we use a semi-empirical model, calibrated with sea-level data of the past millennium, to estimate the SLR implications of holding warming below 2 °C or 1.5 °C above pre-industrial temperature, as mentioned in the Cancún Agreements. Limiting warming to these levels with a probability larger than 50% produces 75-80 cm SLR above the year 2000 by 2100. This is 25 cm below a scenario with unmitigated emissions, but 15 cm above a hypothetical scenario reducing global emissions to zero by 2016. The long-term SLR implications of the two warming goals diverge substantially on a multi-century timescale owing to inertia in the climate system and the differences in rates of SLR by 2100 between the scenarios. By 2300 a 1.5 °C scenario could peak sea level at a median estimate of 1.5 m above 2000. The 50% probability scenario for 2 °C warming would see sea level reaching 2.7 m above 2000 and still rising at about double the present-day rate. Halting SLR within a few centuries is likely to be achieved only with the large-scale deployment of CO2 removal efforts, for example, combining large-scale bioenergy systems with carbon capture and storage.
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China's energy and emissions outlook to 2050: Perspectives from bottom-up energy end-use model
Nan Zhou et al.
Energy Policy, forthcoming
Abstract:
Although China became the world's largest CO2 emitter in 2007, the country has also taken serious actions to reduce its energy and carbon intensity. This study uses the bottom-up LBNL China End-Use Energy Model to assess the role of energy efficiency policies in transitioning China to a lower emission trajectory and meeting its 2020 intensity reduction goals. Two scenarios - Continued Improvement and Accelerated Improvement - were developed to assess the impact of actions already taken by the Chinese government as well as planned and potential actions, and to evaluate the potential for China to reduce energy demand and emissions. This scenario analysis presents an important modeling approach based in the diffusion of end-use technologies and physical drivers of energy demand and thereby help illuminate China's complex and dynamic drivers of energy consumption and implications of energy efficiency policies. The findings suggest that China's CO2 emissions will not likely continue growing throughout this century because of saturation effects in appliances, residential and commercial floor area, roadways, fertilizer use; and population peak around 2030 with slowing urban population growth. The scenarios also underscore the significant role that policy-driven efficiency improvements will play in meeting 2020 carbon mitigation goals along with a decarbonized power supply.
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Projected response of an endangered marine turtle population to climate change
Vincent Saba et al.
Nature Climate Change, November 2012, Pages 814-820
Abstract:
Assessing the potential impacts of climate change on individual species and populations is essential for the stewardship of ecosystems and biodiversity. Critically endangered leatherback turtles in the eastern Pacific Ocean are excellent candidates for such an assessment because their sensitivity to contemporary climate variability has been substantially studied1, 2, 3, 4. If incidental fisheries mortality is eliminated, this population still faces the challenge of recovery in a rapidly changing climate. Here we combined an Earth system model5, climate model projections assessed by the Intergovernmental Panel on Climate Change6 and a population dynamics model to estimate a 7% per decade decline in the Costa Rica nesting population over the twenty-first century. Whereas changes in ocean conditions had a small effect on the population, the ~2.5 °C warming of the nesting beach was the primary driver of the decline through reduced hatching success and hatchling emergence rate. Hatchling sex ratio did not substantially change. Adjusting nesting phenology or changing nesting sites may not entirely prevent the decline, but could offset the decline rate. However, if future observations show a long-term decline in hatching success and emergence rate, anthropogenic climate mitigation of nests (for example, shading, irrigation)7, 8 may be able to preserve the nesting population.
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Assessing the potential impact of climate change on the UK's electricity network
Lynsey McColl et al.
Climatic Change, December 2012, Pages 821-835
Abstract:
We investigate how weather affects the UK's electricity network, by examining past data of weather-related faults on the transmission and distribution networks. By formalising the current relationship between weather-related faults and weather, we use climate projections from a regional climate model (RCM) to quantitatively assess how the frequency of these faults may change in the future. This study found that the incidences of both lightning and solar heat faults are projected to increase in the future. There is evidence that the conditions that cause flooding faults may increase in the future, but a reduction cannot be ruled out. Due to the uncertainty associated with future wind projections, there is no clear signal associated with the future frequency of wind and gale faults, however snow, sleet and blizzard faults are projected to decrease due to a reduction in the number of snow days.
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A Less Cloudy Future: The Role of Subtropical Subsidence in Climate Sensitivity
John Fasullo & Kevin Trenberth
Science, 9 November 2012, Pages 792-794
Abstract:
An observable constraint on climate sensitivity, based on variations in mid-tropospheric relative humidity (RH) and their impact on clouds, is proposed. We show that the tropics and subtropics are linked by teleconnections that induce seasonal RH variations that relate strongly to albedo (via clouds), and that this covariability is mimicked in a warming climate. A present-day analog for future trends is thus identified whereby the intensity of subtropical dry zones in models associated with the boreal monsoon is strongly linked to projected cloud trends, reflected solar radiation, and model sensitivity. Many models, particularly those with low climate sensitivity, fail to adequately resolve these teleconnections and hence are identifiably biased. Improving model fidelity in matching observed variations provides a viable path forward for better predicting future climate.
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Cultural dimensions of climate change impacts and adaptation
Neil Adger et al.
Nature Climate Change, forthcoming
Abstract:
Society's response to every dimension of global climate change is mediated by culture. We analyse new research across the social sciences to show that climate change threatens cultural dimensions of lives and livelihoods that include the material and lived aspects of culture, identity, community cohesion and sense of place. We find, furthermore, that there are important cultural dimensions to how societies respond and adapt to climate-related risks. We demonstrate how culture mediates changes in the environment and changes in societies, and we elucidate shortcomings in contemporary adaptation policy.
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Mapping Greenland's mass loss in space and time
Christopher Harig & Frederik Simons
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
The melting of polar ice sheets is a major contributor to global sea-level rise. Early estimates of the mass lost from the Greenland ice cap, based on satellite gravity data collected by the Gravity Recovery and Climate Experiment, have widely varied. Although the continentally and decadally averaged estimated trends have now more or less converged, to this date, there has been little clarity on the detailed spatial distribution of Greenland's mass loss and how the geographical pattern has varied on relatively shorter time scales. Here, we present a spatially and temporally resolved estimation of the ice mass change over Greenland between April of 2002 and August of 2011. Although the total mass loss trend has remained linear, actively changing areas of mass loss were concentrated on the southeastern and northwestern coasts, with ice mass in the center of Greenland steadily increasing over the decade.
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Rapid coupling between ice volume and polar temperature over the past 150,000 years
K.M. Grant et al.
Nature, forthcoming
Abstract:
Current global warming necessitates a detailed understanding of the relationships between climate and global ice volume. Highly resolved and continuous sea-level records are essential for quantifying ice-volume changes. However, an unbiased study of the timing of past ice-volume changes, relative to polar climate change, has so far been impossible because available sea-level records either were dated by using orbital tuning or ice-core timescales, or were discontinuous in time. Here we present an independent dating of a continuous, high-resolution sea-level record in millennial-scale detail throughout the past 150,000 years. We find that the timing of ice-volume fluctuations agrees well with that of variations in Antarctic climate and especially Greenland climate. Amplitudes of ice-volume fluctuations more closely match Antarctic (rather than Greenland) climate changes. Polar climate and ice-volume changes, and their rates of change, are found to covary within centennial response times. Finally, rates of sea-level rise reached at least 1.2 m per century during all major episodes of ice-volume reduction.
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Ecosystem responses in the southern Caribbean Sea to global climate change
Gordon Taylor et al.
Proceedings of the National Academy of Sciences, 20 November 2012, Pages 19315-19320
Abstract:
Over the last few decades, rising greenhouse gas emissions have promoted poleward expansion of the large-scale atmospheric Hadley circulation that dominates the Tropics, thereby affecting behavior of the Intertropical Convergence Zone (ITCZ) and North Atlantic Oscillation (NAO). Expression of these changes in tropical marine ecosystems is poorly understood because of sparse observational datasets. We link contemporary ecological changes in the southern Caribbean Sea to global climate change indices. Monthly observations from the CARIACO Ocean Time-Series between 1996 and 2010 document significant decadal scale trends, including a net sea surface temperature (SST) rise of ∼1.0 ± 0.14 °C (±SE), intensified stratification, reduced delivery of upwelled nutrients to surface waters, and diminished phytoplankton bloom intensities evident as overall declines in chlorophyll a concentrations (ΔChla = -2.8 ± 0.5%⋅y-1) and net primary production (ΔNPP = -1.5 ± 0.3%⋅y-1). Additionally, phytoplankton taxon dominance shifted from diatoms, dinoflagellates, and coccolithophorids to smaller taxa after 2004, whereas mesozooplankton biomass increased and commercial landings of planktivorous sardines collapsed. Collectively, our results reveal an ecological state change in this planktonic system. The weakening trend in Trade Winds (-1.9 ± 0.3%⋅y-1) and dependent local variables are largely explained by trends in two climatic indices, namely the northward migration of the Azores High pressure center (descending branch of Hadley cell) by 1.12 ± 0.42°N latitude and the northeasterly progression of the ITCZ Atlantic centroid (ascending branch of Hadley cell), the March position of which shifted by about 800 km between 1996 and 2009.
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Warming-induced reductions in body size are greater in aquatic than terrestrial species
Jack Forster, Andrew Hirst & David Atkinson
Proceedings of the National Academy of Sciences, 20 November 2012, Pages 19310-19314
Abstract:
Most ectothermic organisms mature at smaller body sizes when reared in warmer conditions. This phenotypically plastic response, known as the "temperature-size rule" (TSR), is one of the most taxonomically widespread patterns in biology. However, the TSR remains a longstanding life-history puzzle for which no dominant driver has been found. We propose that oxygen supply plays a central role in explaining the magnitude of ectothermic temperature-size responses. Given the much lower oxygen availability and greater effort required to increase uptake in water vs. air, we predict that the TSR in aquatic organisms, especially larger species with lower surface area-body mass ratios, will be stronger than in terrestrial organisms. We performed a meta-analysis of 1,890 body mass responses to temperature in controlled experiments on 169 terrestrial, freshwater, and marine species. This reveals that the strength of the temperature-size response is greater in aquatic than terrestrial species. In animal species of ∼100 mg dry mass, the temperature-size response of aquatic organisms is 10 times greater than in terrestrial organisms (-5.0% °C-1 vs. -0.5% °C-1). Moreover, although the size response of small (<0.1 mg dry mass) aquatic and terrestrial species is similar, increases in species size cause the response to become increasingly negative in aquatic species, as predicted, but on average less negative in terrestrial species. These results support oxygen as a major driver of temperature-size responses in aquatic organisms. Further, the environment-dependent differences parallel latitudinal body size clines, and will influence predicted impacts of climate warming on food production, community structure, and food-web dynamics.