This July 4, 2012 image provided by Ian Joughin, shows surface melt water rushing along the surface of the Greenland Ice Sheet through a supra-glacial stream channel, southwest of Ilulissat, ... more 
This July 4, 2012 image provided by Ian Joughin, shows surface melt water rushing along the surface of the Greenland Ice Sheet through a supra-glacial stream channel, southwest of Ilulissat, Greenland. Polar ice sheets are now melting three times faster than in the 1990s, but so far that's added just less than half an inch to already rising global sea levels, a new giant scientific study says. While the amount of sea level rise isn't as bad as some earlier worst case scenarios, the acceleration of the melting, especially in Greenland, has ice scientists worried. (AP Photo/Ian Joughin) less 
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Associated Press | Photo By Ian Joughin
Thu, Nov 29, 2012 9:02 PM EST