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solonavi 3 May 2007 Climate, Global Warming 122 views No Comment Print This Post  Email This Post

MSNBC

Arctic summer sea ice is melting at a significantly faster rate than projected by even the most advanced computer models, according to a new study that concludes recent U.N. reports on warming underestimate the changes in the Arctic.

The shrinking of summertime ice is about 30 years ahead of the climate model projections, researchers with the National Center for Atmospheric Research and the University of Colorado’s National Snow and Ice Data Center report in the online edition of the peer-reviewed journal Geophysical Research Letters.

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NCAR scientist and co-author Marika Holland added that “while the ice is disappearing faster than the computer models indicate, both observations and the models point in the same direction: the Arctic is losing ice at an increasingly rapid pace and the impact of greenhouse gases is growing.”

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Several possible factors were cited for the disparity:

• The models assume that half of the ice loss was due to increased greenhouse gases, but the study indicates those gases might play a significantly larger role.
• Several models overestimate the thickness of the present-day sea ice.
• The models might fail to fully capture changes in atmospheric and oceanic circulation that transport heat to polar regions.

A world without summer sea ice won’t raise sea levels because that ice is already on water, not land. But it would have a huge impact on polar bears and other wildlife, as well as subsistence hunters. On the other hand, it would also open shorter sea routes, facilitating commerce.

The study was funded by the National Science Foundation and NASA.

Scientists have known that Arctic summer sea ice is melting. The satellite-based illustration at left shows the minimum concentration in 1979, while the one at right shows the minimum in 2005. A new study says the melt is happening faster than recent U.N. reports have factored for.