Climate change has always happened faster in the Arctic than anywhere else,partly because of a sort of accelerating feedback loop. Reflective ice absorbs less heat than dark sea water, so as ice cover gets smaller and smaller, the water gets warmer and warmer. But what happened to the North Pole in 2012 was record-breaking. Arctic sea ice—the ever-changing cap over the top of the globe—melted this summer to just 1.32 million sq. miles (3.41 sq. km), the lowest level since satellite records began in 1979. This year’s minimum extent is 50% smaller than the average between 1979 and 2000. And the melting is unlikely to stop—scientists believe that the Arctic itself could be ice-free during the summer as early as the end of the decade. That has an additional effect on warming—white sea ice reflects sunlight back into space, while dark open water absorbs it, further speeding global warming in a feedback process.