Earlier this week, I found myself driving along the ice-covered route of Interstate 74 through central Illinois. Traveling slowly due to the treacherous conditions, I had plenty of time to observe the apocalyptic wasteland of abandoned cars and twisted tractor-trailers stranded in the snow by those who had been less careful. I also had the time to scan through the dial of radio stations, where I happened upon Rush Limbaugh denouncing the term for the cause of the record-breaking frigid conditions: the polar vortex. In Limbaugh’s words, “Do you know what the polar vortex is? Have you ever heard of it? Well, [the media] just created it for this week… [to make] the case that all of this frigid, chilling cold is due to global warming, strange as it may sound.”
But Limbaugh’s accusation is patently untrue. Meteorologists have long used “polar vortex” as a term for the normal pattern of wind in the Arctic Circle. As illustrated in the above diagram, the region is usually encompassed by wind blowing from the west to the east, powered by the temperature difference between the North Pole and the equator. Jeff Masters, director of meteorology at the website WeatherUnderground, explains that during the Arctic winter, “the 24-hour darkness over the snow and ice-covered polar regions allows a huge dome of cold air to form. This cold air increases the difference in temperature between the pole and the equator, and leads to an intensification of the strong upper-level winds of the jet stream. The strong jet stream winds act to isolate the polar regions from intrusions of warmer air, creating a ‘polar vortex’ of frigid counter-clockwise swirling air over the Arctic.”
The jet stream of the polar vortex can be thought of as a sort of fence, keeping the temperatures of the Arctic away from the more populated regions of the world. When the jet stream weakens, however, this mass of cold air can drift southward, and the cause of this weakening may indeed be tied to global climate change. Normally, the sea ice and snow cover that blanket the Arctic reflect the sun’s energy back into space. Yet both ice and snow in the region have been decreasing over the past several decades, meaning that the area absorbs more energy in the form of heat. This phenomenon decreases the temperature difference between the pole and the equator, which is the driving force of the jet stream.
This complex consequence of warming temperatures has led some scientists to champion the phrase “global weirding” as an alternative to the more widely used global warming. More extreme winter temperatures, heat waves, droughts and storms are all predicted to arise as consequences of man-made emissions. And when the economic consequences of these events become more apparent (the current cold snap is estimated to have cost the US economy $5 billion in lost productivity and counting), even commentators like Limbaugh might take a second look at the underlying science.