Oceans Rising Fast

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OCEANS RISING FAST, NEW STUDIES FIND
Melting ice could raise levels up to 20 feet by 2100, scientists say
David Perlman, Chronicle Science Editor

Friday, March 24, 2006


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Glaciers and ice sheets on opposite ends of the Earth are melting faster than previously thought and could cause sea levels around the world to rise as much as 13 to 20 feet by the end of the century, scientists are reporting today.

If the researchers' estimates are correct, a rise in ocean waters projected by the new studies not only would drown many of the low-lying inhabited atolls and islands that are already endangered by rising ocean waters, it also would threaten coastal cities and harbors on every continent.

Scientists have been warning for decades that greenhouse gases from autos and industry are warming the planet and raising the seas, but the studies appearing today in the journal Science are the first to suggest that sea levels could climb as high as 20 feet as a result of global warming.

The studies by two teams of researchers are the first to combine data on long-term climate change and sea ice melting from both the north and south polar regions.

"This is a real eye-opener set of results," said geoscientist Jonathan T. Overpeck of the University of Arizona, who led one of two teams of university and government climatologists. "We need to start serious measures to reduce greenhouse gases within the next decade, (and) if we don't do something soon, we're committed to 4 to 6 meters (13 to 20 feet) of sea level rise in the future."

The scientists used models of climate change widely accepted by government and university researchers and the fossil record of episodes of global warming thousands of years ago.

The teams, which Overpeck led together with Bette L. Otto-Bliesner, a climatologist at the National Center for Atmospheric Research in Boulder, Colo., analyzed climate and polar ice records from 130,000 years ago during a period of global warming when Earth was tilted somewhat more on its axis than it is today and its orbit around the sun was slightly different. As a result, the sun at that time warmed the north polar regions by about 5 degrees Fahrenheit, Overpeck and his colleagues calculated.

By using evidence from ice cores, stranded coral reefs, fossilized pollen and ancient ocean sediments, the team estimated that Greenland's glaciers and Arctic sea ice all melted rapidly in that period and thrust sea levels up by about 10 feet. Overpeck said that during the same period, the West Antarctic ice sheet, much of which is unstable below sea level, may have also melted along with other ice-clad coasts of Antarctica and added another 10 feet to the rise in global sea level.

The teams then compared that era to what might happen in this century if emissions of carbon dioxide and other industrial gases into the atmosphere continue to increase dramatically, as present trends foresee.

They concluded that ice in both the Artic and Antarctic regions is now melting faster than previously believed and, unless the trend is reversed, that would lead to an average global temperature increase of at least 4 degrees Fahrenheit and a rise from today's global sea level of 13 to 20 feet. Melting of glaciers on Greenland and Arctic sea ice alone could raise sea levels by considerably more than 3 feet, they calculated.

Their conclusions are already provoking controversy -- even among other scientists who are concerned about the impact of greenhouse gases on warming trends but who foresee much smaller increases in future sea levels.

John R. Christy, a noted atmospheric scientist at the University of Alabama who supports the idea that human activities are a major cause of global warming, said in an interview that "these papers don't alarm me. When you look at all the data, it's confusing but not alarming. People are searching for hard answers, and there's still a lot of speculation."

Where Overpeck's team said that "sea level rise could be faster than widely thought," Christy said: "I wish they'd written 'could or could not be faster.' "

On the other side, James Hansen, a leading NASA climate expert who recently accused White House officials of trying to censor his scientific reports, supported the findings.
[Environmental studies have been changed and fudged for years and years and years to serve special interests, which usually means politicians and the businesses that own them]

The work by the two teams "is a useful contribution because they point out that sea level change may be much more rapid than we thought," Hansen said in an e-mail. "The practical problem for humanity is that ice sheet disintegration starts slowly, but once it gets going fast enough it will be out of our control and there will be no way to stop it.

"The further implication is that we have to get serious about reducing greenhouse gas emissions now, not wait 15 years until some magic new technology is available."

Michael Oppenheimer, a Princeton geoscientist and member of the university's Atmospheric and Ocean Sciences Program, agreed with Hansen.

"These are important papers," he said in an interview, "because they provide new insights into the effects of temperature change on melting ice at both poles. They show how even modest increases in global temperatures could put the Earth in a dangerous spot.

"We don't have to know for sure how fast the glaciers and polar ice sheets would disappear to realize that this is a serious warning, and by the end of this century we could be locked into an irreversible trend that no technology could reverse."

In a report that also appears in today's issue of Science, Robert Bindschadler, a glaciologist at NASA's Goddard Space Flight Center in Greenbelt, Md., wrote that Canadian and European satellites monitoring glaciers around the margins of both Greenland and Antarctica provide strong support for the new findings.

Radar aboard the satellites shows that for the past five years, in both the northern and southern regions, warmer waters have been moving into cold ocean layers 3,000 feet deep where the bases of many large glaciers lie, Bindschadler said. The warm waters are rapidly increasing the rate at which those glaciers, as well as deep-rooted sea ice around them, are melting -- and thus are speeding the pace of the rise in sea level, he concluded.
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