Arctic Temperatures Highest in 2,000 Years

Sept. 3, 2009 -- The Arctic is warmer than it's been in 2,000 years, even though it should be cooling because of changes in the Earth's orbit that cause the region to get less direct sunlight.

Indeed, the Arctic had been cooling for nearly two millennia before reversing course in the last century and starting to warm as human activities added greenhouse gases to the atmosphere.

"If it hadn't been for the increase in human-produced greenhouse gases, summer temperatures in the Arctic should have cooled gradually over the last century," said Bette Otto-Bliesner, a National Center for Atmospheric Research scientist and co-author of a study of Arctic temperatures published in Friday's edition of the journal Science.

The most recent 10-year interval, 1999-2008, was the warmest of the last 2,000 years in the Arctic, according to the researchers led by Darrell S. Kaufman, a professor of geology and environmental science at Northern Arizona University.

Summer temperatures in the Arctic averaged 2.5 degrees Fahrenheit (1.4 degrees Celsius) warmer than would have been expected if the cooling had continued, the researchers said.

The finding adds fuel to the debate over a House-passed climate bill now pending in the Senate. The administration-backed measure would impose the first limits on greenhouse gases and eventually would lead to an 80 percent reduction by putting a price on each ton of climate-altering pollution.

WATCH VIDEO: If climate change is evident anywhere in the United States, it's in Alaska.

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It is the latest in a drumbeat of reports on warming conditions in the Arctic, including:

• A marine scientist reports that Alaskan waters are turning acidic from absorbing greenhouse gases faster than tropical waters, potentially endangering the state's $4.6 billion fishing industry.
• NASA satellite measurements show that sea ice in the Arctic is more than just shrinking in area, it is dramatically thinning. The volume of older crucial sea ice in the Arctic has shrunk by 57 percent from the winter of 2004 to 2008.
• Global warming effects in Alaska also include shrinking glaciers, coastal erosion and the march north of destructive forest beetles formerly held in check by cold winters.

And with the melting of land-based ice, such as the massive Greenland ice cap, sea levels could rise across the world, threatening millions who live in coastal cities.