The Cold Truth

Could climate change be to blame for record-low U.S. temps?

November 15, 2014

It's baaaack. (The polar vortex, that is—or rather, its relative, the "Arctic outbreak," as the batch of unseasonably cool weather currently chilling the United States is being called.) Back in January, Jason Bittel explored how unusually frigid weather patterns might be connected to climate change.

So just in case you missed all of those school closingssafety warnings,transportation delaysNFL broadcasts#DeepFreeze tweets, and videos of boiling water turning into insta-ice, you should know that it's cold outside. A "polar vortex" has North America in its icy grip, breaking low temperature records everywhere it goes.

So of course, the climate deniers are out in force, trying to use the #DeepFreeze as proof that global warming is fake. But in fact, it could be just the opposite: some scientists are suggesting that climate change might be making this cold snap all the more bitter.

Let me explain. Though "polar vortex" might sound like some new phrase made up by the Weather Channel, it’s actually a term that meteorologists use to describe large cyclones found at the North and South poles. Polar vortices are always occurringif you remember, they figured prominently in the climate thriller The Day After Tomorrow—but the current extension of the polar vortex this far south is unusual, making it so cold that your tongue would stick to a pole, should you be foolish enough to lick one.

Jennifer Francis, a climatologist at Rutgers University, gets into the nitty-gritty in the video above, but here’s a quick synopsis: It's all about the jet stream, which is like a swirly-twirly river of wind that flows around the Northern Hemisphere, high up in the atmosphere. These currents form a boundary between cold and warm air, with lower temperatures occurring north of the jet stream and higher temperatures to the south. Depending on a number of factors, this boundary can take the shape of a mild S-curve, or it can sometimes resemble the loopy oxbow of a river (which is what it’s doing right now).

One of the factors that dictates how curvy and fast the jet stream becomes is the difference between temperatures at the poles and the equator. The bigger the temperature differential, the faster and straighter these air currents travel. Enter climate change. We know that increased air and ocean temperatures have caused an unprecedented loss of Arctic sea ice. With a warmer Arctic comes a smaller temperature differential and a slower jet stream. And a weak jet stream meanders wildly, not unlike a drunk.

Should this weather wave invert (as it did in the spring of 2012), the same areas that are currently purple and deep blue on the meteorological maps would turn to warmer hues of orange and yellow. For instance, as the Midwest and Northeast shiver, Californians—on the other side of the stream—are enjoying record high temperatures. Making matters worse, weak jet stream patterns have a way of getting stuck (as explained by Weather Underground’s Jeff Masters in the video). And nasty weather that sticks around for a while can turn extreme.

Still, no one can say with certainty that climate change caused this “deep freeze.” After all, every storm front and weather system is the product of several factors, many of which scientists are only beginning to understand. But most climatologists do agree that the probability of extreme weather events has increased with a warming world. As Climate Central’s Andrew Freedman writes:

The state of the science on the links between Arctic warming and weather extremes in the midlatitudes can be likened to a court case. Scientists have gathered reams of mainly circumstantial evidence to prove a suspect’s guilt, or in this case, the existence of an Arctic warming link. But such evidence, which comes in the form of published studies in peer reviewed scientific journals, may not be enough to convince a jury quite yet.

So no smoking gun, but what we do know for sure is that the “polar vortex” was not invented by “the left, the media, everybody” in order to perpetuate the hoax of climate change, as science denier Rush Limbaugh says. Though, at the moment as our fingers and toes go numb, we do appreciate all that hot air Rush and his ilk are blowing our way.

onEarth provides reporting and analysis about environmental science, policy, and culture. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. Learn more or follow us on Facebook and Twitter.

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