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Sunday, March 1, 2009

Jason Box, David Bromwich, Richard Alley: Greenland warming lags, but is bound to catch up -- starting to look slushy

Greenland warming lags, but is bound to catch up

In a Game of Catch-Up
In a Game of Catch-Up | Discovery News Video
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by Michael Reilly, Discovery News, Feb. 27, 2009

One of the world's most important remaining ice reserves on Earth remains deceptively cold.

As the planet's poles thaw out, global sea level rise looms as one of the most dangerous side effects of global warming. Any excess chill may seem like good news for the planet. But a new study suggests that Greenland is lagging behind rest of the northern hemisphere's warming trend and that it's bound to catch up soon.

Air temperatures have been rising steadily in the northern half of the planet since about 1975, when scientists think the effects of human-induced global warming began to dominate the climate. But Greenland was left behind, perhaps kept cool when dust released from the eruptions of Mount St. Helens, El Chicon and Mt. Pinatubo reduced the amount of sunlight hitting the ice.

Around 1985 the icy island started to thaw, and has continued apace ever since. Climate scientists have been alarmed by the speed of the melting, watching as glaciers recede and meltwater pools in lakes on top of the ice.

Still, in an analysis of temperature records in Greenland from 1840 until 2007, Jason Box of Ohio State University and a team of researchers found that the ice sheet remains between 1.0 and 1.5 degrees Centigrade (1.8-2.7 °F) behind the rest of the northern hemisphere. And it should catch up in the coming decades.

"The temperature increase could be three to four times what we've seen already. If that holds it will be far above anything we've seen before," David Bromwich of Ohio State University said. "The ice will continue melting and probably accelerate in the future."

If Greenland's ice sheet ever melts entirely, the results would be catastrophic. The water unleashed into the ocean would be enough to raise sea level 6.5 meters (21.3 ft.), jeopardizing the homes and lives of hundreds of millions of people worldwide.

That's not likely to happen any time soon. But Greenland is already starting to look slushy, and an additional degree or two of warming could be dangerous.

"We've said [in a previous study] that if you sustain between 2 and 7 degrees (3.6-12.6 °F) of warming, Greenland's ice will be gone," Richard Alley of Pennsylvania State University said. "It's already warmed a good chunk of one degree, so if you add another 1-1.5 on top of that, you're at the low end of really worry, and a lot closer to the upper end, too."

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