Columbia Earth Institute - Abrupt Climate Shifts May Be Speedier Than Previously Thought - ENN

[hatrack]

San Francisco-- The United States could suffer the effects of abrupt climate changes within decades—sooner than some previously thought--says a new government report. It contends that seas could rise rapidly if melting of polar ice continues to outrun recent projections, and that an ongoing drought in the U.S. west could be the start of permanent drying for the region. Commissioned by the U.S. Climate Change Science Program, the report was authored by experts from the U.S. Geological Survey, Columbia University's Lamont-Doherty Earth Observatory and other leading institutions. It was released at this week's meeting of the American Geophysical Union.

Many scientists are now raising the possibility that abrupt, catastrophic switches in natural systems may punctuate the steady rise in global temperatures now underway. However, the likelihood and timing of such "tipping points," where large systems move into radically new states, has been controversial. The new report synthesizes the latest published evidence on four specific threats for the 21st century. It uses studies not available to the Intergovernmental Panel on Climate Change (IPCC), whose widely cited 2007 report explored similar questions. "This is the most up to date, as it includes research that came out after IPCC assembled its data," said Edward Cook, a climatologist at Lamont-Doherty and a lead author of the new study.

The researchers say the IPCC's maximum estimate of two feet of sea level rise by 2100 may be exceeded, because new data shows that melting of polar ice sheets is accelerating. Among other things, there is now good evidence that the Antarctic ice cap is losing overall mass. At the time of the IPCC report, scientists were uncertain whether collapses of ice shelves into the ocean off the western Antarctica were being offset by snow accumulation in the continent's interior. But one coauthor, remote-sensing specialist Eric Rignot of the Jet Propulsion Laboratory, told a press conference at the meeting: "There is a new consensus that Antarctica is losing mass." Seaward flow of ice from Greenland is also accelerating. However, projections of how far sea levels might rise are "highly uncertain," says the report, as researchers cannot say whether such losses will continue at the same rates.

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The panel said two other systemic changes seem less imminent, but are still of concern. Vast quantities of methane, a potent greenhouse gas, have long been locked up in ocean sediments, wetlands and permafrost. These could be destabilized by climate change, leading to blowouts of gas, and thus even more abrupt temperature shifts. The panel said blowouts appear unlikely in the next 100 years—but that steady emissions could double, especially in the north, as land and water warm up. The panel also looked at the continuous circulation of the Atlantic Ocean, which sends warm water northward and cold water southward, controlling the climate of western Europe and beyond. Some scientists say this circulation could collapse if enough northern ice melts and dilutes the salty water. The panel found this scenario unlikely in the short term, but warned that the circulation's strength might decline 25% to 30% by 2100. "Abrupt climate change presents potential risks for society that are poorly understood," the researchers write. urgent need for committed and sustained monitoring of those components are particularly vulnerable."

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http://www.enn.com/climate/article/38913

[n2doc]

1. You know, I always thought that I would not live to see the ice caps melt

I am beginning to think I will, unfortunately.

Crap is really going to hit the fan the first time a big city becomes inundated permanently. New Orleans was only the start. If Miami or lower Manhattan goes, the panic is going to be incredible.

[Citizen Number 9]

2. Do you think it will really be panic?

I'm not sure what that would look like as the inundation would probably happen gradually with a few point events for emphasis.

I think what we will see is another slow catastrophe where people first try to sell their (rapidly devaluing) low-lying property then just abandon it to move elsewhere. Of course that will devalue other waterfront property that might not be at immediate risk....

There will be calls for the Fed to step in and assist the folks who have lost their primary asset.

[n2doc]

3. My feeling is, there will be a trigger event

Like Miami getting hit by a hurricane and subsequently becoming uninhabitable because it is under sea level. It seems like things are changing rapidly enough that we may see sea level rise on a noticeable scale, not just mm/year but inches.....