AP - An already relentless melting of the Arctic greatly accelerated this summer, a warning sign that some scientists worry could mean global warming has passed an ominous tipping point./> [Yahoo! News: Science News] 7:31:36 PM comment []
© Copyright 2007 Jonathan Butler.
![An iceberg floats in a bay off Ammassalik Island, Greenland in this July 17, 2007 file photo. A record amount of Greenland's ice sheet melted this summer [~] 13 billion tons more than the previous high mark [~] U.S. scientists are reporting this week in an ominous new sign of global warming. (AP Photo/John McConnico, file)](http://d.yimg.com/us.yimg.com/p/ap/20071211/capt.a6d01972b17346f59d9011be838703b5.arctic_melt_ny348.jpg?x=130&y=86&sig=ifud0PSM.P1Rcu5XyKK11w--)
