Polar meltdown: 2 trillion tons of ice gone in 5 years

More than 2 trillion tons of land ice in Greenland, Antarctica and Alaska have melted since 2003, according to new NASA satellite data that show the latest signs of global warming.

More than half the loss of landlocked ice in the past five years has occurred in Greenland, based on measurements of ice weight by NASA's GRACE satellite, said NASA geophysicist Scott Luthcke.

NASA scientists planned to present their findings on Thursday in San Francisco. Luthcke said Greenland figures for the summer of 2008 aren't complete yet, but this year's ice loss won't be as severe as in 2007.