Nature - U. Washington Study - Tipping Point For Arctic Ice Cap Not Necessarily So - AFP

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There is no "tipping point" beyond which climate change will inevitably push the Arctic ice cap into terminal melt off, according to a study released Wednesday.

The northern polar cap has shrunk between 15 and 20 percent over the last 30 years, unleashing concern that on current trends -- with regional temperature increases twice or triple the global average -- it could disappear entirely during the summer months by century's end.

One of the factors in this calculation is a so-called positive feedback, in which a reduced area of floating ice helps to stoke global warming. As ice cover recedes decade by decade, more of the Sun's radiative force is absorbed by dark-blue sea rather than bounced back into space by reflective ice and snow.

But a new study published in the British science journal Nature shows that there is nothing inevitable about this process, and that it can be halted or even reversed. "There is no 'tipping point' that would result in unstoppable loss of summer sea ice when greenhouse gas-driven warming rose above a certain threshold," said Steven Amstrup, a professor at the University of Washington and lead author of the study.

EDIT

http://www.spacedaily.com/reports/Arctic_icecap_safe_from_runaway_melting_study_999.html