Paul Krugman has become pretty famous for being able to peer into the complex economy and find something to justify whatever he is promoting. Higher interest rates, lower interest rates, more growth, less growth, unemployment, or boom times all simultaneously are proof of whatever theory he currently holds (which, in turn, is generally exactly the theory required to support actions by the Democratic leadership).
In the same way -- hot weather, cold weather, drought, wet weather, mild weather, lost of hurricanes, a lack of hurricanes -- are all simultaneously the proof for man-made global warming. Whatever the weather currently is, someone can use a government grant to build a model to prove that it is due to anthropogenic global warming. Thus this story -- Global warming causing freezing.