Melting ice threatens coast cities

At the current warming rate, the Arctic will be 4 degrees higher by 2100.
WASHINGTON (AP) -- Low-lying communities such as New Orleans and Miami could face increasing peril as melting polar ice raises the ocean to levels not seen in thousands of years.
By the end of this century, Arctic temperatures could reach as high as 130,000 years ago, when the oceans were 13 to 20 feet higher than now, according to research appearing in today's issue of the journal Science.
That doesn't mean the water would rise that much by 2100 -- more likely 3 feet or so, the researchers say. But it would launch a process that would continue for long after, and even 3 feet could affect populated areas around the planet and increase the potential damage from storms.
The principal findings:
At the current warming rate, Earth's temperature by 2100 will probably be at least 4 degrees higher than now, with the Arctic at least as warm as it was 130,000 years ago, reports a research group led by Jonathan T. Overpeck of the University of Arizona.
Computer models indicate that warming could raise the average temperature in parts of Greenland above freezing for multiple months and could have a substantial impact on melting of the polar ice sheets, says a second paper by researchers led by Bette Otto-Bliesner of the National Center for Atmospheric Research. Melting could raise sea level 1 to 3 feet over the next 100 to 150 years, she said.
And a team led by Goeran Ekstroem of Harvard University reported an increase in "glacial earthquakes," which occur when giant rivers of ice -- some as big as Manhattan -- move suddenly as meltwater eases their path. That sudden movement causes the ground to tremble.
Otto-Bliesner and Overpeck wrote separate papers and also worked together, studying ancient climate and whether modern computer climate models correctly reflect those earlier times. That allowed them to use the models to look at possible future conditions. The researchers studied ancient coral reefs, ice cores and other natural climate records.
"Although the focus of our work is polar, the implications are global," Otto-Bliesner said. "These ice sheets have melted before and sea levels rose. The warmth needed isn't that much above present conditions."
According to the studies, increases in greenhouse gases in the atmosphere over the next century could raise Arctic temperatures as much as 5 to 8 degrees.
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