Know Your Anomaly

NASA Earth Observatory image

If you live in western Canada or the Continental U.S., your problem has a name: the Arctic Oscillation. Normally, low air pressure over the Arctic keeps cold air trapped at high latitudes. But if southern-latitude barometric pressure drops, the atmospheric dike between north and south weakens and arctic air leaks out, chilling the continent’s middle and giving the Arctic a bit of a break from the cold. Not that that’s always a good thing: Iqualit, Nunavut’s New Year snowmobile parade was cancelled due to the unusual warmth.

In the image from NASA above, deep red indicates a surface-temperature anomaly of 18 degrees above normal; deep blue marks locales 18 degrees above their average temperature for this time of year. Note that the reds aren’t necessarily warmer than than the blues; the colors indicate departures from local norms. Also note: this isn’t the phenomenon formerly known as global warming. It’s weather. One of the strange effects of climate change might be the disruption or disappearance of the Arctic Oscillation, which itself is a normal periodic occurrence. Tired of all the snow? Be careful what you wish for. —via NASA’s Earth Observatory

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