Scientists Blame Dramatic Weather On Weakening 'Arctic Fence'

Many parts of Europe and the U.S. have seen unusual snowstorms and frigid temperatures for two years in a row. But places like northern Canada and Greenland have seen temperatures that in some months are running 15 to 20 degrees above average.

The reason, some researchers say, is a weakening "vortex," a kind of atmospheric fence, that normally keeps cold air up north and warmer air south. We speak with Justin Gillis, who covers climate issues for the New York Times, about why the weather world seems to have flipped upside down.