Brutal cold weather is gripping much of Canada and the U.S. today, as a 'polar vortex' treks down from the north, and while it may seem contradictory, global warming is playing a role in the spread of this bitter cold.
Even with Canada and the U.S. experiencing a more 'normal' winter this year, after two very mild winters thanks to the El Nino-La Nina pattern in the Pacific, this kind of extreme weather is still not what we usually see. We're certainly used to cold, snowy weather, but this shot of bone-chilling cold is coming at us from what's known as a 'polar vortex'.
This may sound like something out of the disaster movie, The Day After Tomorrow, or maybe a made-up name to make headlines sound more urgent and scary. However, the polar vortex is very real. In the northern hemisphere, these strong circulations of frigid air typically hang out over the north pole, trapping most of the extreme cold over the Arctic. The jet stream — that wavy 'ribbon' of extremely strong winds that wraps itself around the world — is the southern edge of where the polar vortex is spinning. The strength of the vortex depends on there being a big difference in temperatures between the Arctic and the equatorial regions.