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Forecast sea level rise may be overestimated by some models
mongabay.com
September 4, 2008


Global sea level rise is unlikely to exceed 2 meters (6 1/2 feet) by the end of century argues a new study published in the journal Science.

The researchers, led by Tad Pfeffer of the University of Colorado at Boulder, say that a global sea level rise by the end of the century will likely be in the 0.2 to 2 meter (30 to 80-inch) range, less than the 4-9 meters (12-30 feet) projected by some of the more extreme models.

"We consider glaciological conditions required for large sea level rise to occur by 2100 and conclude increases of 2 meters are physically untenable," the authors wrote. "We find that a total sea level rise of about 2 meters by 2100 could occur under physically possible glaciological conditions but only if all variables are quickly accelerated to extremely high limits."

"The gist of the study is that very simple, physical considerations show that some of the very large predictions of sea level rise are unlikely, because there is simply no way to move the ice or the water into the ocean that fast," said Pfeffer, lead author of the study and a fellow of CU-Boulder's Institute of Arctic and Alpine Research.

"For Greenland alone to raise sea level by two meters by 2100, all of the outlet glaciers involved would need to move more than three times faster than the fastest outlet glaciers ever observed, or more than 70 times faster than they presently move. And they would have to start moving that fast today, not 10 years from now. It is a simple argument with no fancy physics."

While Pfeffer notes that even a 0.9-meter (three-foot) rise in sea level would have serious consequences for low-lying coastal regions, he says that improved forecasting will help make better use of resources to prepare for future change.

"If we plan for 6 feet and only get 2 feet, for example, or visa versa, we could spend billions of dollars of resources solving the wrong problems," he said.

CITATION: W. T. Pfeffer, J. T. Harper, S. O’Neel (2008). Kinematic Constraints on Glacier Contributions to 21st-Century Sea-Level Rise. 5 SEPTEMBER 2008 VOL 321 SCIENCE