GLOBAL WARMING

2 trillion tons of ice melted

Between Greenland, Antarctica and Alaska, melting land ice has raised global sea levels about one-fifth of an inch in the past five years

AP

WASHINGTON. 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 what scientists say is global warming.

More than half of 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. The water melting from Greenland in the past five years would fill up about 11 Chesapeake Bays, he said, and the Greenland melt seems to be accelerating.

NASA scientists planned to present their findings Thursday at the American Geophysical Union conference in San Francisco.

Luthcke said Greenland figures for the summer of 2008 aren't complete yet, but this year's ice loss, while still significant, won't be as severe as 2007.

The news was better for Alaska. After a precipitous drop in 2005, land ice increased slightly in 2008 because of large winter snowfalls, Luthcke said. Since 2003 Alaska has lost 400 billion tons of land ice.

In assessing climate change, scientists generally look at several years to determine a trend.

Melting of land ice, unlike sea ice, increases sea levels very slightly. In the 1990s, Greenland didn't add to world sea level rise; now that island is adding about half a millimeter of sea level rise a year, NASA ice scientist Jay Zwally said in a telephone interview from the conference.

Between Greenland, Antarctica and Alaska, melting land ice has raised global sea levels about one-fifth of an inch in the past five years, Luthcke said.

Other research, being presented this week at the geophysical meeting point to more melting concerns from global warming, especially with sea ice.

"It's not getting better; it's continuing to show strong signs of warming and amplification," Zwally said. "There's no reversal taking place."

Scientists studying sea ice will announce that parts of the Arctic north of Alaska were 9 to 10 degrees warmer this past fall, a strong early indication that the Arctic is warming faster than predicted.

As sea ice melts, the Arctic waters absorb more heat in the summer. That absorbed heat is released into the air in the fall, leading to autumn temperatures today that are six to 10 degrees warmer than in the 1980s, said research scientist Julienne Stroeve at the National Snow and Ice Data Center in Boulder, Colo. That's a strong and early impact of global warming, she said.

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