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Enhanced Seasonal Exchange of CO2 by Northern Ecosystems Since 1960
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Seasonal variations of atmospheric carbon dioxide (CO2) in the Northern Hemisphere have increased since the 1950s, but sparse observations have prevented a clear assessment of the patterns of long-term change and the underlying mechanisms. We compare recent aircraft-based observations of CO2 above the North Pacific and Arctic Oceans to earlier data from 1958 to 1961 and find that the seasonal amplitude at altitudes of 3 to 6 km increased by 50% for 45° to 90°N but by less than 25% for 10° to 45°N. An increase of 30 to 60% in the seasonal exchange of CO2 by northern extratropical land ecosystems, focused on boreal forests, is implicated, substantially more than simulated by current land ecosystem models. The observations appear
to signal large ecological changes in northern forests and a major shift in the global carbon cycle.
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Pathways for Conservation
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NEXT WEEK, CONSERVATION SCIENTISTS WILL GATHER AT THE INTERNATIONAL CONGRESS FOR
Conservation Biology (ICCB) in Baltimore, Maryland, to grapple with the challenges of
preserving our natural world in the face of a growing and increasingly consumptive human
population. The natural world provides countless services, such as clean water, protection
from fl ooding, and carbon sequestration, while offering opportunities for new medicines,
foods, and energy production. Yet these valuable services and opportunities are disappearing
along with the species and natural areas that supply them. The needs of a growing human
population must be met while conserving the planet’s natural systems. Accomplishing both
will depend on making clearer connections between scientifi c results regarding issues such
as biodiversity loss and the critical decisions that must be made about conditions that underlie
change, such as greenhouse gas emissions and freshwater availability. The good news is
that today’s conservation scientists are developing innovative tools
and strategies.
SCIENCE VOL 341
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A Reconstruction of Regional and Global Temperature for the Past 11,300 Years
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Surface temperature reconstructions of the past 1500 years suggest that recent warming is
unprecedented in that time. Here we provide a broader perspective by reconstructing regional
and global temperature anomalies for the past 11,300 years from 73 globally distributed
records. Early Holocene (10,000 to 5000 years ago) warmth is followed by ~0.7°C cooling
through the middle to late Holocene (<5000 years ago), culminating in the coolest temperatures
of the Holocene during the Little Ice Age, about 200 years ago. This cooling is largely
associated with ~2°C change in the North Atlantic. Current global temperatures of the past
decade have not yet exceeded peak interglacial values but are warmer than during ~75% of
the Holocene temperature history. Intergovernmental Panel on Climate Change model projections
for 2100 exceed the full distribution of Holocene temperature under all plausible greenhouse
gas emission scenarios.
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Is Embracing Change Our Best Bet?
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Restoration ecology and conservation
biology are both under pressure to
adapt to accelerated anthropogenic
global change. Pristine areas free from human
infl uence no longer exist and, arguably, have
not for thousands of years ( 1). Major landcover
transformations for agriculture affected
vast territories more than 3000 years ago ( 2).
Large mammal extinctions in the late Pleistocene
(circa 12,000 years ago) were related to
human expansion ( 3). And relocation of nowwidespread
naturalized species was already
happening 4230 years ago, when domestic
dogs (dingos) were introduced into Australia
by way of southeast Asia ( 4). Thus, humansculpted
landscapes are what we have been
mostly managing for millennia. Because the
rate of alteration has dramatically increased
over the past 200 years, those ancient localized
impacts now affect most of the world.
Additionally, other indirect impacts act at a
planetary scale—e.g., increased carbon dioxide
concentration and nitrogen deposition
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Hell and High Water: PracticeRelevant Adaptation Science
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Adaptation requires science that analyzes decisions, identifies vulnerabilities, improves foresight, and develops options
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Marine Taxa Track Local Climate Velocities
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Organisms are expected to adapt or move in response to climate change, but observed
distribution shifts span a wide range of directions and rates. Explanations often emphasize
biological distinctions among species, but general mechanisms have been elusive. We tested an
alternative hypothesis: that differences in climate velocity—the rate and direction that climate
shifts across the landscape—can explain observed species shifts. We compiled a database of
coastal surveys around North America from 1968 to 2011, sampling 128 million individuals
across 360 marine taxa. Climate velocity explained the magnitude and direction of shifts in
latitude and depth much more effectively than did species characteristics. Our results demonstrate
that marine species shift at different rates and directions because they closely track the complex
mosaic of local climate velocities.
SCIENCE VOL 341 13 SEPTEMBER 2013
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Monsoon Melee
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The rhythms of life across South Asia depend on the Indian monsoon. Climate scientists
are locking horns over the cause of the summer deluges
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Climate Change Conversations
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THE THOUSANDS OF PRESENTATIONS AT NEXT WEEK’S MEETING OF THE AMERICAN CHEMICAL SOCIETY (ACS) in New Orleans exemplify one of the many ways scientists converse among themselves
about the most recent advances in science. Science and technology continue to reshape the
world we live in, and appreciating how these changes, both intended and unintended, come
about is a necessity for all citizens in a democratic society. Scientists have a responsibility to
help their fellow citizens understand what science and technology can and cannot do for them
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The Global Plight of Pollinators
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Wild pollinators are in decline, and managed
honeybees cannot compensate for their loss.
29 MARCH 2013 VOL 339 SCIENCE
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Wildlife decline and social conflict
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Policies aimed at reducing
wildlife-related conflict
must address the
underlying causes
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