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Saturday, March 25, 2006

Cities Under The Sea?

The curious thing is that this post isn't about Plato, and the mythical submerged city of Atlantis, rather it is about a report in Scientific American based on a study which is published today in 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.

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.......

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.

Now anyone with just a smattering of background in the modelling issues which arise in macro-economics will be only too well aware of the modelling problems attached to such complex processes and the margins of error likely to be associated with any such forceasts, yet there is obviously still plenty of food for thought here.

Clearly there are alternative theories, and I still think it is a very open issue whether the long run consequences may not be substantial global cooling (which could be an even worse problem), but there you are. One possibility to keep in mind.

Science has a very interesting collection of material here.