June 18, 2008
June 12, 2008
To the astonishment of climate specialists, an analysis of ice extracted from the full depth of the Greenland ice sheet has shown that except for the 8,000 to 10,000 years since the last glacial epoch, the climate over the past 250,000 years has changed frequently and abruptly.
The findings suggest that the period of stable climate in which human civilization has flourished might be unusual, and that the current climate may get either warmer or colder much more quickly than had been believed -- in spans of decades or even less.
The data are likely to bolster concern that future changes in climate might not be spread over many centuries, allowing farmers to adjust to altered growing conditions and coastal cities to deal with rising sea levels, for example.
Scientists have speculated for years about the effects of climate warming. Even a rise of a few feet in sea level would flood many food-producing regions and populous areas.
Commenting on the new research, Dr. Andrew J. Weaver of the University of Victoria in British Columbia said that if the climate became colder Europe would be covered with snow much longer. As glaciers advanced, he said, they would reflect more of the Sun's energy back into space, chilling the climate even more. Warmer and Colder Periods
The scientists said their data showed that significantly warmer periods and significantly colder periods had occurred during the last interval between glacial epochs, about 115,000 to 135,000 years ago. They said they could not tell whether that meant similar changes were in store. Their findings were reported today in two papers in the journal Nature.
Previous studies had shown that there were abrupt changes in climate during glacial epochs, but the new results show that the same was true in the periods when glaciers had retreated. In one "catastrophic event" during the last interglacial period, the average temperature plunged 25 degrees Fahrenheit to ice-age levels for about 70 years, the scientists reported.
The authors said they did not have an explanation for the rapid shifts. They also said it was a mystery why the climate of the last 8,000 to 10,000 years had been "strangely stable."
Thanks to Neal Boortz for the link.
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