Quick on the Thaw

Melting Arctic sea ice may have hit point of no return, scientists fear

Experts on the climate of the Arctic have been busy this summer altering their dire predictions for a globally warmed future -- to make them even direr. According to scientists at the National Snow and Ice Data Center at the University of Colorado, the Arctic's sea ice has been gradually retreating since about 1978 -- no surprise there -- but the trend has worsened in the last four years or so to the point where the climate system may be unable to recover. Since September 2002, the ice has failed to make any sort of significant comeback in the winter. Worried researchers point to a vicious cycle of melted ice exposing more ocean -- a better heat absorber than ice -- to the sun, leading to more ice loss, leading to more exposed ocean, and so on. Says an Arctic ice specialist at Cambridge University, "You're essentially changing land into ocean ... [which] will have a very big impact on other climate parameters." Though vast quantities of melted sea ice alone wouldn't raise sea levels*, experts worry the rapid changes to the Arctic's climate might also lead to rapid melting of Greenland's glaciers, which could dramatically affect ocean levels.

*[Clarification, 20 Sep 2005: This summary originally implied that the melting of sea ice would raise sea levels, which isn't the case.]