Arctic Sea Ice Is Melting Fast

Arctic sea ice is melting at a much faster rate than projected by the most advanced computer models, says a government-funded study published online May 1 in Geophysical Research Letters (DOI: 10.1029/2007GL029703, 2007).

In February, the United Nations Intergovernmental Panel on Climate Change concluded on the basis of computer models that September sea ice in the Arctic had declined an average of 2.5% per decade between 1953 and 2006. (September marks the yearly minimum of Arctic sea ice.) In the new study, scientists from the National Center for Atmospheric Research (NCAR) and the National Snow & Ice Data Center, in Boulder, Colo., compared decades of measurements by ships, airplanes, and satellites and found that the area of September sea ice actually declined 7.8% per decade over that period. As a consequence, they predict that if greenhouse gas emissions are not reduced, the Arctic will be ice-free in September as soon as 2020.

"Although the ice is disappearing faster than the computer models indicate, both the observations and the models point in the same direction: The Arctic is losing ice at an increasingly rapid pace, and the impact of greenhouse gases is growing," says NCAR scientist Marika M. Holland, one of the study???s coauthors.