He measured the minimum extent of sea ice in each region - and that revealed the much higher rate of loss. The trend is continuing. This past summer, "we had the least amount of permanent ice cover ever observed," says Comiso.

"If the permanent ice cover disappears, the entire Arctic ocean climate and ecology would become very different," says Comiso, at NASA's Goddard Space Flight Center in Greenbelt, Maryland. It will give an extra kick to global warming and polar bears, which live by hunting on the sea ice, will have nowhere to go.