Sunday, September 23, 2007

Submergency! Three-foot sea level rise ahead.

More scientists have just come out and told it like it is. The AP story by Seth Borenstein is less about what its title says - Rising Seas Likely to Flood U.S. History - and more about the certainty of two dozen climatologists that the sea level will rise by at least 3 feet no matter what we do to slow global warming.

Global warming — through a combination of melting glaciers, disappearing ice sheets and warmer waters expanding — is expected to cause oceans to rise by one meter, or about 39 inches. It will happen regardless of any future actions to curb greenhouse gases, several leading scientists say. And it will reshape the nation.

Rising waters will lap at the foundations of old money Wall Street and the new money towers of Silicon Valley. They will swamp the locations of big city airports and major interstate highways.

There are discrepancies between the scientists' estimations of when the 3-foot rise metric will be reached; some say 50 years, some 100, and some 150. However long it takes, the sea will be rising up to that point, maybe inch-by-inch, maybe in larger steps.

Sea level rise is "the thing that I'm most concerned about as a scientist," says Benjamin Santer, a climate physicist at the Lawrence Livermore National Laboratory in California.

"We're going to get a meter and there's nothing we can do about it," said University of Victoria climatologist Andrew Weaver, a lead author of the February report from the Intergovernmental Panel on Climate Change in Paris. "It's going to happen no matter what — the question is when."

Sea level rise "has consequences about where people live and what they care about," said Donald Boesch, a University of Maryland scientist who has studied the issue. "We're going to be into this big national debate about what we protect and at what cost."

This is why I'm most concerned about sea level rise. It affects almost everything and everybody and it's not temporary. The sea goes's gonna stay there a good long time. And as it goes up, how do we know what to plan for? Will it stop at 3 feet of rise? Not necessarily or even probably. Some climatologists can envision a 20-foot rise and more.

As Joe Romm and Jim Hansen keep telling us, SHUT DOWN COAL EMISSIONS. Somehow, today, preferably yesterday, but tomorrow at least. Joe is a bit more optimistic than the least optimistic of the scientists interviewed, but he admits we're using up our window of opportunity to get the energy producers and governments to put a lid on coal. As Joe explains:

My point — and I think Hansen’s point — is that the “when” (i.e. the rate of change) matters a lot! One meter by mid-century would be an unmitigated catastrophe. Sea level rise would have to average 9 inches a decade from now to 2050, implying seas rising over a foot a decade by then — which could continue for centuries. Who could adapt to that?

Strong actions to limit further emissions starting today — what Hansen calls the alternative scenario — can limit total warming from preindustrial levels to about 2°C, which should keep sea level rise below one meter per century. That’s a disaster, but a slow-moving one, leaving time for some adaptation. And if we were lucky, the rate might be well below a meter per century.

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