This winter's weather does not reveal anything about global warming

Last month in Science, a group of five prominent atmospheric scientists from around the country published a letter cautioning us not to interpret this winter's severe weather through the lens of climate change (Wallace et al., 2014). This winter has witnessed the dip in the polar vortex over much of the U.S., resulting in all time low temperatures; there have also been a series of heavy snowstorms on the east coast. Speaking of these events, the authors write:

Some have been touting such stretches of extreme cold as evidence that global warming is a hoax, while others have been citing them as evidence that global warming is causing a “global weirding” of the weather. In our view, it is neither.

As climate scientists, we share the prevailing view in our community that human-induced global warming is happening and that, without mitigating measures, the Earth will continue to warm over the next century with serious consequences. But we consider it unlikely that those consequences will include more frigid winters.

Although such a hypothesis has been proposed, the authors do not find it corroborated with either “alternate observational analyses” nor climate model simulations. Moreover they “do not view the theoretical arguments underlying it as compelling.” The authors caution about mistaking coincidence for causation, and although they believe such hypotheses “deserve a fair hearing”, the authors seem to imply that this one is too half-baked to be made “the centerpiece of the public discourse on global warming.” They conclude:

Even in a warming climate, we could experience an extraordinary run of cold winters, but harsher winters in future decades are not among the most likely nor the most serious consequences of global warming.

Reference

John M. Wallace, Isaac M. Held, David W. J. Thompson, Kevin E. Trenberth, and John E. Walsh, 2014: Global warming and winter weather. Science, 343: 729-730.