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WASHINGTON (Reuters) - The world's sea levels could rise twice as high this century as U.N. climate scientists have predicted, according to researchers who looked at what happened more than 100,000 years ago, the last time Earth got this hot.
Experts working on the U.N.'s Intergovernmental Panel on Climate Change have suggested a maximum 21st century sea level rise -- a key effect of global climate change -- of about 32 inches.
But researchers said in a study appearing on Sunday in the journal Nature Geoscience that the maximum could be twice that, or 64 inches.
They made the estimate by looking at the so-called interglacial period, some 124,000 to 119,000 years ago, when Earth's climate was warmer than it is now due to a different configuration of the planet's orbit around the sun.
That was the last time sea levels reached up to 20 feet (6 meters) above where they are now, fueled by the melting of the ice sheets that cover Greenland and Antarctica.
The researchers say their study is the first robust documentation of how quickly sea levels rose to that level.
"Until now, there have been no data that sufficiently constrain the full rate of past sea level rises above the present level," lead author Eelco Rohling of Britain's National Oceanography Centre said in a statement.
Rohling and his colleagues found an average sea level rise of 64 inches each century during the interglacial period.
Back then, Greenland was 5.4 to 9 degrees Fahrenheit warmer than now -- which is similar to the warming period expected in the next 50 to 100 years, Rohling said.
Current models of ice sheet activity do not predict rates of change this large, but they do not include many of the dynamic processes already being observed by glaciologists, the statement said.
Editing by Xavier Briand