Many unsuspecting states were recently surprised with some unusually cold temperatures. According to Los Angeles Times writer Matt Pearce, Atlanta reached a record low of 6 degrees. South Carolina, Florida, Georgia and Texas felt the brunt of the polar vortex. The polar vortex is made up of wind currents that circle the North Pole. Think of it like a spinning top. Like a top, the polar vortex will sometimes tip to one side. However, unlike a top, when the polar vortex tips, it releases extremely cold air.
As it turns out, the tipping action may have been a direct result of global warming.

When you think of global warming, you think hot temperatures. It refers to the rise in average temperature across the world, causing record highs and the polar caps to melt.
Around there is usually where our mental picture of global warming ends. What we fail to think about is the enormous effects of all those high temperatures and melted ice.
The warming of the arctic may have actually caused a change in the jet stream, which led to the tipping of the polar vortex. Between the North Pole and the equator, there is a balance of heat, which directly affects the upper level winds of the jet stream. Manmade climate change may have upset the balance, causing a shift of the wind flow.

While the polar vortex has finally lifted, we can expect to see more extreme weather events in the future.

Sources:
http://www.latimes.com/nation/la-na-deep-freeze-20140108,0,2384395.story#axzz2q78yWGNB
http://www.cnn.com/2014/01/06/us/polar-vortex-explained/
http://www.climatecentral.org/news/polar-vortex-in-u.s.-may-be-valid-example-of-global-warming-16927