Monday, April 30, 2007

"Arctic sea ice melts faster than thought"

Arctic sea ice is melting three times faster than many scientists project, U.S. researchers reported Monday, just days ahead of the next major international report on climate change.

Scientists at the National Center for Atmospheric Research and the University of Colorado in Boulder concluded that Arctic sea ice has declined at an average rate of about 7.8 percent per decade between 1953 and 2006.

By contrast, 18 computer models used by the Intergovernmental Panel on Climate Change, a U.N.-sponsored climate research group, estimated an average rate of decline of 2.5 percent per decade over the same period, the researchers said.

International delegates are meeting in Bangkok, Thailand, this week to hammer out the final wording of the third IPCC report.

Both the observations cited in the new study and projections from the IPCC computer models are for September, when Arctic sea ice is typically at its low point for the year.

For March, when the ice is typically at its most extensive, the new study found the rate of decline was 1.8 percent per decade, about three times larger than the mean from the computer models.

The researchers said their observations indicate the retreat of summertime Arctic sea ice is about 30 years ahead of the pace projected by climate models...

They said the discrepancy between their observations and computer projections indicate computer models may have failed to portray the entire impact of increasing levels of greenhouse gases such as carbon dioxide in the atmosphere.

The computer models indicated that increased greenhouse gases and natural climate variations were about equally responsible for ice loss between 1979 and 2006, the researchers said.

They said their own study indicates greenhouse gases may have a "significantly greater" role than the models suggested.

For more info - see: Geophysical Research Letters

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