Ominous Arctic melt worries experts

http://news.yahoo.com/s/ap/20071211/ap_on_sc/arctic_melt;_ylt=ArE9.Y4L0i7gZvS9OhzJpFas0NUE

Melting of sea ice and Greenland's ice sheets also alarms scientists because they become part of a troubling spiral.

White sea ice reflects about 80 percent of the sun's heat off Earth, NASA's Zwally said. When there is no sea ice, about 90 percent of the heat goes into the ocean which then warms everything else up. Warmer oceans then lead to more melting.

"That feedback is the key to why the models predict that the Arctic warming is going to be faster," Zwally said. "It's getting even worse than the models predicted."

NASA scientist James Hansen, the lone-wolf researcher often called the godfather of global warming, on Thursday was to tell scientists and others at the American Geophysical Union scientific in San Francisco that in some ways Earth has hit one of his so-called tipping points, based on Greenland melt data.

"We have passed that and some other tipping points in the way that I will define them," Hansen said in an e-mail. "We have not passed a point of no return. We can still roll things back in time — but it is going to require a quick turn in direction."
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