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Stationarity Is Dead: Whither Water Management?
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Climate change undermines a basic assumption
that historically has facilitated management of
water supplies, demands, and risks.
SCIENCE VOL 319
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A Determination of the Cloud Feedback from Climate Variations over the Past Decade
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Estimates of Earth's climate sensitivity are uncertain, largely because of uncertainty in the
long-term cloud feedback. I estimated the magnitude of the cloud feedback in response to short-term
climate variations by analyzing the top-of-atmosphere radiation budget from March 2000 to February
2010. Over this period, the short-term cloud feedback had a magnitude of 0.54 T 0.74 (2s) watts
per square meter per kelvin, meaning that it is likely positive. A small negative feedback is possible,
but one large enough to cancel the climate’s positive feedbacks is not supported by these observations.
Both long- and short-wave components of short-term cloud feedback are also likely positive.
Calculations of short-term cloud feedback in climate models yield a similar feedback. I find no
correlation in the models between the short- and long-term cloud feedbacks.
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Modeling Effects of Environmental Change on Wolf Population Dynamics, Trait Evolution, and Life History
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Environmental change has been observed to generate simultaneous responses in population dynamics,
life history, gene frequencies, and morphology in a number of species. But how common are such
eco-evolutionary responses to environmental change likely to be? Are they inevitable, or do they
require a specific type of change? Can we accurately predict eco-evolutionary responses? We
address these questions using theory and data from the study of Yellowstone wolves. We show that
environmental change is expected to generate eco-evolutionary change, that changes in the
average environment will affect wolves to a greater extent than changes in how variable it is, and
that accurate prediction of the consequences of environmental change will probably prove elusive.
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Beyond Predictions: Biodiversity Conservation in a Changing Climate
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Climate change is predicted to become a major threat to biodiversity in the 21st century,
but accurate predictions and effective solutions have proved difficult to formulate. Alarming
predictions have come from a rather narrow methodological base, but a new, integrated science
of climate-change biodiversity assessment is emerging, based on multiple sources and
approaches. Drawing on evidence from paleoecological observations, recent phenological and
microevolutionary responses, experiments, and computational models, we review the insights that
different approaches bring to anticipating and managing the biodiversity consequences of
climate change, including the extent of species’ natural resilience. We introduce a framework
that uses information from different sources to identify vulnerability and to support the design of
conservation responses. Although much of the information reviewed is on species, our framework
and conclusions are also applicable to ecosystems, habitats, ecological communities, and
genetic diversity, whether terrestrial, marine, or fresh water.
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The Hot Summer of 2010: Redrawing the Temperature Record Map of Europe
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The summer of 2010 was exceptionally warm in eastern
Europe and large parts of Russia. We provide evidence
that the anomalous 2010 warmth that caused adverse
impacts exceeded the amplitude and spatial extent of the
previous hottest summer of 2003. 'Mega-heatwaves' such
as the 2003 and 2010 events broke the 500-yr long
seasonal temperature records over approximately 50% of
Europe. According to regional multi-model experiments,
the probability of a summer experiencing 'megaheatwaves'
will increase by a factor of 5 to 10 within the
next 40 years. However, the magnitude of the 2010 event
was so extreme that despite this increase, the occurrence
of an analogue over the same region remains fairly
unlikely until the second half of the 21st century.
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Global Resilience of Tropical Forest and Savanna to Critical Transitions
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It has been suggested that tropical forest and savanna could represent alternative stable states,
implying critical transitions at tipping points in response to altered climate or other drivers.
So far, evidence for this idea has remained elusive, and integrated climate models assume smooth
vegetation responses. We analyzed data on the distribution of tree cover in Africa, Australia,
and South America to reveal strong evidence for the existence of three distinct attractors:
forest, savanna, and a treeless state. Empirical reconstruction of the basins of attraction indicates
that the resilience of the states varies in a universal way with precipitation. These results allow
the identification of regions where forest or savanna may most easily tip into an alternative
state, and they pave the way to a new generation of coupled climate models.
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Time to Adapt to a Warming World, But Where’s the Science?
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With dangerous global warming seemingly inevitable, users of climate information—
from water utilities to international aid workers—are turning to climate scientists for
guidance. But usable knowledge is in short supply
VOL 334 SCIENCE
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The 2010 Amazon Drought
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Several global circulation models (GCMs)
project an increase in the frequency and
severity of drought events affecting the
Amazon region as a consequence of anthropogenic
greenhouse gas emissions (1). The proximate
cause is twofold, increasing Pacific sea surface
temperatures (SSTs), which may intensify El Niño
Southern Oscillation events and associated periodic
Amazon droughts, and an increase in the frequency
of historically rarer droughts associated with
high Atlantic SSTs and northwest displacement of
the intertropical convergence zone (1, 2). Such
droughts may lead to a loss of some Amazon forests,
which would accelerate climate change (3).
In 2005, a major Atlantic SST–associated drought
occurred, identified as a 1-in-100-year event (2).
Here, we report on a second drought in 2010, when
Atlantic SSTs were again high.
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Climate Outlook Looking Much The Same, or Even Worse
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Climate scientists have been feverishly preparing analyses for inclusion in the fifth climate assessment report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) due out in 2013. At the meeting, they gave colleagues a peek at where climate science stands 5 years after their last push to inform the authoritative international evaluation . The climate models are bigger and more sophisticated
than ever, speakers reported, but they are yielding the same wide range of possible warming and precipitation changes as they did 5 years ago. But when polled on other areas of concern, researchers say they see more trouble ahead than the previous IPCC assessment had, though less than some scientists had feared
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The Global Extent and Determinants of Savanna and Forest as Alternative Biome States
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Theoretically, fire–tree cover feedbacks can maintain savanna and forest as alternative stable states.
However, the global extent of fire-driven discontinuities in tree cover is unknown, especially accounting
for seasonality and soils. We use tree cover, climate, fire, and soils data sets to show that tree cover is
globally discontinuous. Climate influences tree cover globally but, at intermediate rainfall (1000 to
2500 millimeters) with mild seasonality (less than 7 months), tree cover is bimodal, and only fire
differentiates between savanna and forest. These may be alternative states over large areas, including
parts of Amazonia and the Congo. Changes in biome distributions, whether at the cost of savanna (due to
fragmentation) or forest (due to climate), will be neither smooth nor easily reversible.
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