Florida's Global Warming Future
By the end of this century, Earth would be at least 4 degrees F (2.3 degrees C) warmer than now, or about as hot as it was nearly 130,000 years ago.
Back then, significant portions of the Greenland and Antarctic ice sheets melted, pushing the global sea levels to about 20 feet higher than current levels.
A similarly dramatic, and in some cases catastrophic, rise in ocean levels could happen by the year 2500, Overpeck said in a telephone interview, but he noted it could come sooner.
"We know when the sea level was that high in the past, and we know how much warming is necessary to get that amount of sea level rise from both Greenland and Antarctica," Overpeck said.
The Earth will get that hot sometime early in the second half of this century, he said, and once it does, the big ice sheets will start melting "in a more dramatic manner" than they currently are.
A conservative estimate would call for sea level rises of 3 feet (1 meter) per century, he said.
He cautioned, however, that this estimate assumes the Earth will get only as hot as it did 130,000 years ago when the ice sheets melted.
"If we decide to keep on the track we're on now and just keep on warming, because of greenhouse gas pollution, then we could easily cook those ice sheets more rapidly," Overpeck said.
The earlier ice melt was concentrated in the Northern Hemisphere in the summer months, and was due largely to changes in Earth's orbit, he said.
"The climate warming we're in now is global and it's year-round and it's due to human influences on the climate system," he said. "That will be more damaging to the ice sheets than the that warming we had 130,000 years ago."
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