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A long-term perspective on a modern drought in the American Southeast
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The depth of the 2006–9 drought in the humid, southeastern US left several metropolitan areas
with only a 60–120 day water supply. To put the region’s recent drought variability in a long-term
perspective, a dense and diverse tree-ring network—including the first records throughout the
Apalachicola–Chattahoochee–Flint river basin—is used to reconstruct drought from 1665 to 2010
CE. The network accounts for up to 58.1% of the annual variance in warm-season drought during
the 20th century and captures wet eras during the middle to late 20th century. The reconstruction
shows that the recent droughts are not unprecedented over the last 346 years. Indeed, droughts of
extended duration occurred more frequently between 1696 and 1820. Our results indicate that the
era in which local and state water supply decisions were developed and the period of instrumental
data upon which it is based are amongst the wettest since at least 1665. Given continued growth
and subsequent industrial, agricultural and metropolitan demand throughout the southeast, insights
from paleohydroclimate records suggest that the threat of water-related conflict in the region has
potential to grow more intense in the decades to come.
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A megacity in a changing climate: the case of Kolkata
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Projections by the Intergovernmental Panel on Climate Change suggest that there will be an increase in the frequency and intensity of climate extremes in the 21st century. Kolkata, a megacity in India, has been singled out as one of the urban centers vulnerable to climate risks. Modest flooding during monsoons at high tide in the Hooghly River is a recurring hazard in Kolkata. More intense rainfall, riverine flooding, sea level rise, and coastal storm surges in a changing climate can lead to widespread and severe flooding and bring the city to a standstill for several days. Using rainfall data, high and low emissions scenarios, and sea level rise of 27 cm by 2050, this paper assesses the vulnerability of Kolkata to increasingly intense precipitation events for return periods of 30, 50, and 100 years. It makes location-specific inundation depth and duration projections using hydrological, hydraulic, and urban storm models with geographic overlays. High resolution spatial analysis provides a roadmap for designing adaptation schemes to minimize the impacts of climate change. The modeling results show that de-silting of the main sewers would reduce vulnerable population estimates by at least 5 %.
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A statistical procedure to determine recent climate change of extreme daily meteorological data as applied at two locations in Northwestern North America
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An iterative chi-square method is applied to determine recent climate change of extremes of daily minimum temperature at two locations between an 18- year recent period and a 36-year prior period. The method determines for each of two locations in northwestern North America, Bozeman, Montana, USA and Coldstream, British Columbia, Canada, which values of the extreme daily weather elements are most significantly different between the prior years and the recent years and gives a measure of the weekly significance of that difference. Determination was made of the average percent of each recent year date (plotted weekly) that was im- pacted by extreme weather due to climate change as well as the percentage change in the frequency of the number of extreme days for each period of contiguous significant weeks. During the recent period at both locations, most weeks experienced a greater number of days of extreme high minimum temperature and a fewer number of days of extreme low minimum temperature. The weekly percentage changes indicate that extreme high minimum temperatures at both Bozeman and Coldstream are increasing at the rate of about 10% per decade, with a close corresponding decrease of extreme low minimum temperatures. The major changes in climate were very similar at both locations, with greatest warming occurring during the late winter and early spring and during the late July to August period.
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Adapting to a Changing Climate in the Southeast
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Whether it’s change to native terrestrial habitats or sea level rise and impacts to vital coastal wetlands and marshes, we are only beginning to understand what is happening across the country, what is likely to occur in the years ahead, and how our agency will act. Indeed, of the 128 national wildlife refuges in the Southeast more than half are located along the coast. The number of days per year with peak temperatures over 90F is expected to rise significantly. By the end of this century, projections indicate much of North Carolina will have 90F plus days for one-third of the year, up from less than 30 days in that temperature zone in the 1960s and 1970s. Arkansas will see 90F days for up to 150 days a year, and NorthFlorida for nearly 6 months a year.
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Amazon Basin climate under global warming: the role of the sea surface temperature
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The Hadley Centre coupled climate–carbon cycle model (HadCM3LC) predicts loss of the Amazon
rainforest in response to future anthropogenic greenhouse gas emissions. In this study, the
atmospheric component of HadCM3LC is used to assess the role of simulated changes in midtwenty-first
century sea surface temperature (SST) in Amazon Basin climate change. When the full HadCM3LC SST anomalies (SSTAs) are used, the atmosphere model reproduces the Amazon Basin climate change exhibited by HadCM3LC, including much of the reduction in Amazon Basin rainfall. This rainfall change is shown to be the combined effect of SSTAs in both thetropical Atlantic and the Pacific, with roughly equal contributions from each basin. The greatest rainfall reduction occurs from May to October, outside of the mature South American monsoon (SAM) season. This dry season response is the combined effect of a more rapid warming of the tropical North Atlantic relative to the south, and warm SSTAs in the tropical east Pacific. Conversely,
a weak enhancement of mature SAM season rainfall in response to Atlantic SST change is suppressed
by the atmospheric response to Pacific SST. This net wet season response is sufficient to prevent dry
season soil moisture deficits from being recharged through the SAM season, leading to a perennial
soil moisture reduction and an associated 30% reduction in annual Amazon Basin net primary
productivity (NPP). A further 23% NPP reduction occurs in response to a 3.58C warmer air
temperature associated with a global mean SST warming.
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Amid Worrisome Signs of Warming, ‘Climate Fatigue’ Sets In
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As scientists debate whether climate is changing faster than anticipated, some worry that a
drumbeat of dire warnings may be helping to erode U.S. public concerns about global warming
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An extreme climatic event alters marine ecosystem structure in a global biodiversity hotspot
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Extreme climatic events, such as heat waves, are predicted to increase in frequency and magnitude as a consequence of global warming but their ecological effects are poorly understood, particularly in marine ecosystems1–3. In early 2011, the marine ecosystems along the west coast of Australia -- a global hotspot of biodiversity and endemism 4,5 -- experienced the highest-magnitude warming event on record. Sea temperatures soared to unprecedented levels and warming anomalies of 2–4 ◦ C persisted for more than ten weeks along >2,000 km of coastline. We show that biodiversity patterns of temperate seaweeds, sessile invertebrates and demersal fish were significantly different after the warming event, which led to a reduction in the abundance of habitat-forming seaweeds and a subsequent shift in community structure towards a depauperate state and a tropicalization of fish communities. We conclude that extreme climatic events are key drivers of biodiversity patterns and that the frequency and intensity of such episodes have major implications for predictive models of species distribution and ecosystem structure, which are largely based on gradual warming trends.
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Approaching a state shift in Earth’s biosphere
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Localized ecological systems are known to shift abruptly and irreversibly from one state to another when they are forced across critical thresholds. Here we review evidence that the global ecosystem as a whole can react in the same way and is approaching a planetary-scale critical transition as a result of human influence. The plausibility of a planetary-scale ‘tipping point’ highlights the need to improve biological forecasting by detecting early warning signs of critical transitions on global as well as local scales, and by detecting feedbacks that promote such transitions. It is also necessary to address root causes of how humans are forcing biological changes.
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Are we in the midst of the sixth mass extinction? A view from the world of amphibians
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Many scientists argue that we are either entering or in the midst of the sixth great mass extinction. Intense human pressure, both direct and indirect, is having profound effects on natural environ- ments. The amphibians—frogs, salamanders, and caecilians—may be the only major group currently at risk globally. A detailed worldwide assessment and subsequent updates show that one- third or more of the 6,300 species are threatened with extinction. This trend is likely to accelerate because most amphibians occur in the tropics and have small geographic ranges that make them susceptible to extinction. The increasing pressure from habitat destruction and climate change is likely to have major impacts on narrowly adapted and distributed species. We show that salamanders on tropical mountains are particularly at risk. A new and significant threat to amphibians is a virulent, emerging infec- tious disease, chytridiomycosis, which appears to be globally distributed, and its effects may be exacerbated by global warming. This disease, which is caused by a fungal pathogen and implicated in serious declines and extinctions of >200 species of amphibians, poses the greatest threat to biodiversity of any known disease. Our data for frogs in the Sierra Nevada of California show that the fungus is having a devastating impact on native species, already weakened by the effects of pollution and introduced predators. A general message from amphibians is that we may have little time to stave off a potential mass extinction.
chytridiomycosis climate change population declines Batrachochytrium dendrobatidis emerging disease
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Autopsy of two mega-heatwaves
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Record-breaking heatwaves in 2003 and 2010 surprised both the public and experts. Observations provide new insights into how temperatures escalated to unprecedented values through the interaction of boundary-layer dynamics and land surface drying.
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