Future Sea Level Rise

The Earth may be warm enough by 2100 for widespread melting of the Greenland Ice Sheet and partial collapse of the Antarctic Ice Sheet, according to two new papers in the 24 March 2006 issue of Science that feature model comparisons of Earth’s climate 129,000 years ago and over the next century.

Bette Otto-Bliesner and colleagues used a combination of paleoclimate data, a climate model, and an ice sheet model to determine how large the Greenland Ice Sheet was during the last interglacial, about 129,000 years ago, when sea level was several meters higher than it is today. On the basis of their reconstruction of surface temperatures at that time, they estimate that the Greenland Ice Sheet and other Arctic ice fields contributed between 2.2 and 3.4 meters of sea level rise during the second-most-recent deglaciation.

In the related paper, Jonathan Overpeck and colleagues compared the same model's predictions of warming over the next 130 years to the climate reconstruction presented in the Otto-Bliesner et al. paper, and conclude that surface temperatures will be as high by the end of the 21st century as they were 129,000 years ago. If the past is a guide to the future, then conditions with the potential to melt enough of the Greenland and Antarctic ice sheets to raise sea level by several meters may exist by the end of the 21st century.

Daniel B. Kane

24 March 2006