Sunday, March 04, 2007

In my initial post on the Intergovernmental Panel on Climate Change 4th Assessment Report (IPCC AR4), I discussed some errors made in the compilation of data on Global Sea Level (GSL). Table SPM-0 in the AR4 suggested that GSL is currently rising at a rate of 1.8 ± 0.5 mm/yr (18 ± 5 cm/100 yr). However, the authors did not appear to have much confidence in their estimate or the contribution that might be made by melting of Antarctic and Greenland ice. In comments that I made on several blogs at the time, I suggested that the present panel may have lacked the expertise needed to develop a model of ice sheet melting and isostatic response by the Earth's crust.

A paper has just been published in Physics Today, coauthored by a physicist and a climatologist, which takes a stab at a comprehensive evaluation of GSL and possible effects from 20th century global warming. The authors show Holocene rates along the shores of the North American continent to be most rapid in the Mid-Atlantic region due to the presence of the proglacial forebulge, which peaks over the Chesapeake Bay. Maximum rates of 2 mm/yr might be explained by a suite of natural forcing factors, although the authors favor either increasing thermal expansion due to warm sea surface temperatures or some small contributions from the melting of Antarctic or Greenland ice.

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