Increased melt

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, reported Newsminer.com Tuesday.

Newsminer quotes the NASA geophysicist Scott Luthcke as saying that more than half of the loss of terrestial ice in the past five years has occurred in Greenland, based on measurements of ice weight by NASA's GRACE satellite, and the Greenland melt seems to be accelerating.

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, when the NASA satellite started taking measurements, Alaska has lost 400 billion tons of land ice.

In assessing climate change, scientists generally look at several years to determine the overall 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. Sea levels also rise as a result water expanding as it warms.