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Scientists have found other indications of global cooling. For one thing there has been a noticeable expansion of the great belt of dry, high-altitude polar winds —the so-called circumpolar vortex—that sweep from west to east around the top and bottom of the world.

Another Ice Age? – TIME
http://content.time.com/time/magazine/article/0,9171,944914,00.html

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But not only does the cold spell not disprove climate change, it may well be that global warming could be making the occasional bout of extreme cold weather in the U.S. even more likely. Right now much of the U.S. is in the grip of a polar vortex, which is pretty much what it sounds like: a whirlwind of extremely cold, extremely dense air that forms near the poles. Usually the fast winds in the vortex—which can top 100 mph (161 k/h)—keep that cold air locked up in the Arctic. But when the winds weaken, the vortex can begin to wobble like a drunk on his fourth martini, and the Arctic air can escape and spill southward, bringing Arctic weather with it. In this case, nearly the entire polar vortex has tumbled southward, leading to record-breaking cold

Polar Vortex: Climate Change Could Be the Cause of Record Cold Weather
http://science.time.com/2014/01/06/climate-change-driving-cold-weather/