|Ice sheets melting far faster than in 1990s, study finds||11/30/12|
Predictions were way off. It's much faster than thought.Associated Press
Greenland ice is melting over 5 times faster than in recent times
Fueled by global warming, polar ice sheets in Greenland and Antarctica are now melting three times faster than they did in the 1990s, a new scientific study says.
So far, that's only added about half an inch to rising sea levels, not as bad as some earlier worst case scenarios. But the melting's quicker pace, especially in Greenland, has ice scientists worried.
One of the biggest wild cards in climate change has been figuring out how much the melting of the massive sheets of ice at the two poles would add to the seas. Until now, researchers haven't agreed on how fast the mile-thick sheets are thawing - and if Antarctica was even losing ice.
The new research concludes that Antarctica is melting, but points to the smaller ice sheet in Greenland, which covers most of the island, as the bigger and more pressing issue. Its melt rate has grown from about 55 billion tons a year in the 1990s to almost 290 billion tons a year recently, according to the study.
"Greenland is really taking off," said National Snow and Ice Data Center scientist Ted Scambos, a co-author of the paper released Thursday by the journal Science.
Study lead author Andrew Shepherd of the University of Leeds in England, said their results provide a message for negotiators in Doha, Qatar, who are working on an international agreement to fight global warming: "It's very clear now that Greenland is a problem."
Scientists blame man-made global warming for the melting. Burning fossil fuels, such as coal and oil, emits carbon dioxide and other gases that trap heat, warming the atmosphere and oceans. Bit-by-bit, that erodes the ice sheets from above and below. Snowfall replenishes the ice sheets, but hasn't kept pace with the rate of melting.
Because the world's oceans are so big, it takes a lot of ice melting—about 10 trillion tons—to raise sea levels 1 inch. Since 1992, ice sheets at the poles have lost nearly 5 trillion tons of ice, the study says, raising sea levels by about a half inch.
That seemingly tiny extra bit probably worsened the flooding from an already devastating superstorm Sandy last month, said NASA ice scientist Erik Ivins, another co-author of the study. He said the extra weight gives each wave a little more energy.
"The more energy there is in a wave, the further the water can get inland," Ivins said.
Globally, the world's oceans rose about half a foot on average in the 20th century. Melting ice sheets account for about one-fifth of sea level rise. Warmer water expands, contributing to the rise along with water from melting glaciers outside the polar regions.
Just how much ice is melting at the two poles has been difficult for scientists to answer. In 2007, the Intergovernmental Panel on Climate Change did not include ice sheet melt in its calculations of future sea level rise because numbers were so uncertain.
It's an important factor because if all the polar ice sheets somehow melted - something that would take centuries - global sea levels would jump by more than 200 feet, said Pennsylvania State University ice scientist Richard Alley, who wasn't part of the research.
From Science Magazine:
Experts Agree Global Warming Is Melting the World Rapidly
Richard A. Kerr
Forty-seven glaciologists have arrived at a community consensus over all the data on what the past century's warming has done to the great ice sheets: a current annual loss of 344 billion tons of glacial ice, accounting for 20% of current sea level rise. Greenland's share—about 263 billion tons—is roughly what most researchers expected, but Antarctica's represents the first agreement on a rate that had ranged from a far larger loss to an actual gain. The new analysis, published on page 1183 of this week's issue of Science, also makes it clear that losses from Greenland and West Antarctica have been accelerating, showing that some ice sheets are disconcertingly sensitive to warming.
[Editor's Note: A word to the wise, on behalf of your grandchildren's grandchildren: If you are within 50 miles of the coast, as 50% of Americans are, consider movoing inland to higher ground, and northward, while the window is open and your coastline property is still dry and valuable. And plant hybrid Chestnut trees, so your progeny will always have something to eat. Expectation: government, owned by corporations now, will not be able to respond effectively, or in time. Forget the dikes. It's time for yikes.]
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