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Ancient climate
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Shellfish could supplant tree-ring climate data

Oxygen isotopes in clamshells may provide the most detailed record yet of global climate change, according to a team of scientists who studied a haul of ancient Icelandic molluscs.
Most measures of palaeoclimate provide data on only average annual temperatures, says William Patterson, an isotope chemist at the University of Saskatchewan in Saskatoon, Canada, and lead author of the study. But molluscs grow continually, and the levels of different oxygen isotopes in their shells vary with the temperature of the water in which they live. The colder the water, the higher the proportion of the heavy oxygen isotope, oxygen-18.

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-- Edited by Blobrana on Monday 8th of March 2010 09:36:50 PM

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Were short warm periods typical for transitions between interglacial and glacial epochs in prehuman times?

At the end of the last interglacial epoch, around 115,000 years ago, there were significant climate fluctuations. In Central and Eastern Europe, the slow transition from the Eemian Interglacial to the Weichselian Glacial was marked by a growing instability in vegetation trends with possibly at least two warming events. This is the finding of German and Russian climate researchers who have evaluated geochemical and pollen analyses of lake sediments in Saxony-Anhalt, Brandenburg and Russia. Writing in Quaternary International, scientists from the Helmholtz Centre for Environmental Research (UFZ), the Saxon Academy of Sciences (SAW) in Leipzig and the Russian Academy of Sciences say that a short warming event at the very end of the last interglacial period marked the final transition to the ice age.
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Fossilised coral reefs in the Great Barrier Reef could help scientists understand how sea levels have changed over the past 20,000 years.
An international team of researchers will spend 45 days at sea, gathering core samples from about 40 sites.
Described as the "trees of the sea", coral have growth rings that show seasonal variations.

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Precise measurements of sea level from Mediterranean caves have revealed that about 81,000 years ago the seas stood much higher than previously thought - even higher than today's levels. The finding may force scientists to reconsider how Earth's large ice sheets wax and wane in response to changing climate.
Changes in global sea level are used to trace the fluctuations of ice sheets. As ice sheets advanced from a low-point around 125,000 years ago to a maximum around 20,000 years ago, sea level fell - although there was plenty of variation along the way. 125,000 years ago, seas stood roughly at today's heights, whereas at the last glacial maximum, sea levels were 130 metres lower than at present.
But a group led by Jeffrey Dorale, a geologist at the University of Iowa in Iowa City, now suggests that 81,000 years ago the sea level increased sharply to reach a high-point, roughly one metre above today's level

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Cave Reveals Southwest's Abrupt Climate Swings During Ice Age

Ice Age climate records from an Arizona stalagmite link the Southwest's winter precipitation to temperatures in the North Atlantic, according to new University of Arizona research.
The finding is the first to document that the abrupt changes in Ice Age climate known from Greenland also occurred in the southwestern U.S., said co-author Julia E. Cole, a UA professor of geosciences.

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A team led by Yale University geologists has reconstructed the climate and elevation of California's northern Sierra Nevada mountains using organic materials derived from ancient leaves and bacteria. Their findings, published in the January issue of the journal Geology, show that the Sierra Nevada was warmer in the past and was a prominent topographic feature at least 50 million years ago, helping to resolve long-standing questions regarding the tectonic history of the mountain range.
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Meteor hit unlikely cause for climate change

It's "very unlikely" that a meteor or asteroid colliding with the Earth caused an abrupt climate change leading to the extinction of the woolly mammoth and other large mammals 13,000 years ago, says the University of Hawaii at Manoa leader of a team that investigated the theory.
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Younger Dryas
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Big freeze plunged Europe into ice age in months
In the film, 'The Day After Tomorrow' the world enters the icy grip of a new glacial period within the space of just a few weeks. Now new research shows that this scenario may not be so far from the truth after all.
William Patterson, from the University of Saskatchewan in Canada, and his colleagues have shown that switching off the North Atlantic circulation can force the Northern hemisphere into a mini 'ice age' in a matter of months. Previous work has indicated that this process would take tens of years.

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Unusually warm and cold periods in Earth's pre-industrial climate history are linked to how the oceans responded to temperature changes, say scientists.
The researchers focused particularly on intervals known as the "little ice age" and "medieval warm period".

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Cave Study Links Climate Change to California Droughts
California experienced centuries-long droughts in the past 20,000 years that coincided with the thawing of ice caps in the Arctic, according to a new study by UC Davis doctoral student Jessica Oster and geology professor Isabel Montaņez.
The finding, which comes from analysing stalagmites from Moaning Cavern in the central Sierra Nevada, was published online November 5, 2009 in the journal Earth and Planetary Science Letters.

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