Arctic ice melt is accelerating even faster than the most recent projections - temperatures over the past six years are the highest since measurements began in 1880.
A study released today concludes that average global sea level could rise by as much as five feet during this century, according to the international Arctic Monitoring and Assessment Program. The study is one of the most comprehensive updates on climate change in the Arctic, and builds on a similar assessment in 2005.
The report says that feedback mechanisms that would accelerate warming in the climate system have now started kicking in.
The ocean is absorbing more heat because less of it is covered by ice, which would otherwise reflect the sun's energy.
Ice cover has been at or near record lows since 2001, says the report, which predicts the Arctic Ocean will be nearly ice free during the summer within 30-40 years.
"The observed changes in sea ice on the Arctic Ocean, in the mass of the Greenland ice sheet and Arctic ice caps and glaciers over the past 10 years are dramatic and represent an obvious departure from long-term patterns," says the report.
Yearly mass loss from Greenland's ice sheet, which covers an area the size of Mexico, increased from 50 gigatons in 1995-2000 to more than 200 gigatons in 2004-2008.
The report projects that average fall and winter temperatures in the Arctic will climb by 5.4-10.8 F (3-6 C) by 2080, unless greenhouse gas emissions are drastically reduced.
