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Climate Model Predicts Greater Melting, Submerged Cities

Over the past 30 years, temperatures in the Arctic have been creeping up,
rising half a degree Celsius with attendant increases in glacial melting and
decreases in sea ice. Experts predict that at current levels of greenhouse
gases--carbon dioxide alone is at 375 parts per million--the earth may warm
by as much as five degrees Celsius, matching conditions roughly 130,000
years ago. Now a refined climate model is predicting, among other things,
sea level rises of as much as 20 feet, according to research results
published today in the journal Science.

Modeler Bette Otto-Bliesner of the National Center for Atmospheric Research
in Boulder and paleoclimatologist Jonathan Overpeck of the University of
Arizona matched results from the Community Climate System Model and climate
records preserved in ice cores, exposed coral reefs, fossilized pollen and
the chemical makeup of shells to determine the accuracy of the computer
simulation. Roughly 130,000 the Arctic enjoyed higher levels of solar
radiation, leading to increased warming in the summer and the retreat of
glaciers worldwide. The model correctly predicted the extent of the
resulting Arctic ice melt, enough to raise sea levels by roughly nine feet.

"Getting the past climate change correct in these models gives us more
confidence in their ability to predict future climate change," Otto-Bliesner
says. "These ice sheets have melted before and sea levels rose. The warmth
needed isn't that much above present conditions."
But sea levels rose as much as 20 feet 130,000 years ago and Overpeck
speculates that may have been the result of additional melting in
Antarctica. After all, the ice there is not all landlocked; some rests in
the ocean and a little warming in sea temperatures could melt it or pry it
loose. And this time around, the warming is global, rather than concentrated
in the Arctic. "In the Antarctic, all you have to do is break up the ice
sheet and float it away and that would raise sea level," he says. "It's just
like throwing a bunch of ice cubes into a full glass of water and watching
the water spill over the top."


Such a sea level rise would permanently inundate low-lying lands like New
Orleans, southern Florida, Bangladesh and the Netherlands. Already sea level
rise has increased to an inch per decade, thanks to melting ice and warm
water expansion, according to Overpeck. And evidence that the Arctic is
exponentially warming continues to accumulate. Indeed, in another paper in
the same issue of Science, Goran Ekstrom of Harvard University reported a
marked increase in so-called glacial earthquakes (seismic events recorded
throughout the world when Greenland's glaciers slip past rock) since 2002.
In fact, last year alone saw twice as many quakes as in previous years, with
most of that increase coming during the summer months.
"We need to start serious measures to reduce greenhouse gases within the
next decade," Overpeck says. "If we don't do something soon, we're committed
to [13 to 20 feet] of sea level rise in the future." --David Biello