Scientists at the National Center for Atmospheric Research and the University of Colorado in Boulder concluded, using actual measurements, that Arctic sea ice has declined at an average rate of about 7.8% 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% 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% 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.
News Release: From the National Center for Atmospheric Research
Arctic Ice Retreating More Quickly Than Computer Models Project: Arctic sea ice is melting at a significantly faster rate than projected by even the most advanced computer models, a new study concludes. The research, by scientists at the National Center for Atmospheric Research (NCAR) and the University of Colorado's National Snow and Ice Data Center (NSIDC), shows that the Arctic's ice cover is retreating more rapidly than estimated by any of the 18 computer models used by the Intergovernmental Panel on Climate Change (IPCC) in preparing its 2007 assessments.
Click here or on image to enlarge.
The figure above illustrates the extent to which Arctic sea ice is melting faster than projected by computer models. The dotted line represents the average rate of melting indicated by computer models, with the blue area indicating the spread among the different models (shown as plus/minus one standard deviation). The red line shows the actual rate of Arctic ice loss based on observations. The observations have been particularly accurate since 1979 because of new satellite technology. (Illustration by Steve Deyo, ©UCAR, based on research by NSIDC and NCAR