Last month, climate scientists announced that Arctic sea ice had shrunk to its smallest surface area since satellite observations began in 1979. An ice-free summer in the Arctic, once projected to be more than a century away, now looks possible just a few decades from now. Some scientists say it may happen within the next few years.
The loss is hugely significant because Arctic sea ice reflects most solar energy into space, helping to keep the Earth at a moderate temperature. But when the ice melts it reveals dark waters below, which absorb more than 90 percent of the solar energy that hits them, leading to faster warming both locally and globally.
Peter Wadhams, professor of ocean physics at Cambridge University, warns that the Arctic may be ice-free in summer as soon as 2015. Such a massive loss would have a warming effect roughly equivalent to all human activity to date. In other words, a summer ice-free Arctic could double the rate of warming of the planet as a whole. No wonder that leading NASA climate scientist James Hansen says bluntly: "We are in a planetary emergency."