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Climate change has made severe cold spells like the one that recently gripped the Northeast far less common than they used to be, a team of researchers has found.

The reason is straightforward: The Arctic has warmed so much — twice as fast in recent decades than other parts of the world — that when polar air descends to lower latitudes, the cold snaps are warmer on average. So a spell of extremely cold weather like the recent one is rare, about 15 times rarer than a century ago, the scientists said.