The much-hyped "Polar Vortex" that plunged much of North America into dangerously low temperatures is giving the climate change denialist crowd an opportunity to gloat—and, typically, display their ignorance. Bloomberg on Jan. 7 presented a sneering Tweet from Donald Trump dismissing global warming as "bullshit" because the "planet is freezing." But the Bloomberg account, as well as a video on the Greenpeace Blog, quotes Rutgers University climate researcher Jennifer Francis explaining how the Vortex was likely unleashed by—yup, global warming! It seems that the Jet Stream, which normally serves as a boundary separating cold air to the north from warm air to the south, is being destabilized; receding arctic sea ice lessens the temperature difference either side of the Stream, thereby slowing its velocity and causing large loops and meanders to form, and even for it to get "stuck." When this happens, North America and Europe are going either into extreme heat or extreme cold, depending on where the jet gets jammed. Recent record-breaking highs in Chicago and Fairbanks, as well as shriveling heat waves across the Great Plains, may have been caused by the same phenomenon now sending the mercury plunging in the Midwest and Northeast.
We we have noted (repeatedly) that "global warming" is actually a misleading term, allowing the denialists to gloat at every cold snap. What we are looking at is better understood as climate destabilization. Others have called it "global weirding," portending more extreme weather rather than a steady and uniform rise in temperature everywhere around the word. (More at Time's Ecocentric blog, Jan. 6)