http://www.npr.org/2014/01/07/260408972/polar-vortex-blames-...
http://www.npr.org/2015/12/15/459871063/climate-change-plays...
two NPR links here, the 2014 says how the cold in winter 2014 is the polar vortex, and the warm in 2015 is a combination of tight polar vortex and el nino, he* resisted saying it was related to climate change.
he is Mike Halpert, NOAA's deputy director of the Climate Prediction Center