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That’s the massive storm, the “Great Groundhog’s Day Blizzard of 2011,” that is just now clearing out of the Great Plains and pummeling the Northeast.
If you’re interested in the technical side of weather, as always, I’ll point you to Jeff Master’s analysis of the storm.
But seeing as I’ve already heard a couple of “So much for global warming, huh?” comments uttered by well meaning, but ill-informed people around the country, it’s my duty to, once again, address it.
I know I’m being a broken record (skip…skip…skip…skip…skip…skip…) about weather and climate but, honestly, I can’t blame people for looking at an absurdly intense North American winter and thinking, “Is this really what global warming looks like?”
Actually, it probably is. And thankfully, meteorologists and climate experts are getting better at explaining it.
Back in December, we wrote about some theories on why a warmer arctic could mean a colder North America and Northern Europe.
Andrew Freedman writes on Capitol Weather Gang, “The unusually wintry weather gripping Europe as well as the cold plaguing the eastern United States are linked by a historically strong weather system locked over Greenland.” Believe it or not, this frigid start to winter in northern North America and Europe may have to do with unusually warm temperatures in the Arctic.
And as Climate Central explained this “Warm Arctic/Cold Continents Pattern,” linking the loss of sea ice to the cold northerly blasts.
When the ice melts, it allows incoming solar radiation to warm water and air temperatures, which in turn has an influence on atmospheric pressure and circulation, and may help shift Arctic air southward, while the Arctic remains unusually warm.
Last week, NASA released this map that helps illustrate this point.
This map of the United States, Canada, eastern Siberia, and Greenland shows temperature anomalies for January 9 to 16, 2011, compared to the same dates from 2003 through 2010…Because this image shows temperature anomalies rather than absolute temperatures, red or orange areas are not necessarily warmer than blue areas. The reds and blues indicate local temperatures that are warmer or colder than the norm for that particular area. The overall configuration of warmer-than-normal temperatures in the north and cooler-than-normal temperatures in the south probably results from a climate pattern known as the Arctic Oscillation (AO).
So while the beginning of January was unusually frigid down in most of the country, temperature at higher latitudes were abnormally warm. So warm that residents of Iqaluit, the capital Nunavut in far northern Canada, had to cancel their New Year’s snowmobile parade. So what exactly is this Arctic Oscillation, anyways? I’ll leave it to NASA to explain:
The AO is a pattern of differences in air pressure between the Arctic and mid-latitudes. When the AO is in “positive” phase, air pressure over the Arctic is low, pressure over the mid-latitudes is high, and prevailing winds confine extremely cold air to the Arctic. But when the AO is in “negative” phase, the pressure gradient weakens. The air pressure over the Arctic is not quite so low, and air pressure at mid-latitudes is not as high. In this negative phase, the AO enables Arctic air to slide south and warm air to slip north.
The big question is how exactly this Arctic Oscillation is being impacted by loss of sea ice and generally warmer surface and ocean temperatures. NOAA’s recent “Arctic Report Card” is the best resource so far for answers. The very basic formula seems to be: warmer Arctic temperatures lead to loss of sea ice in the Arctic, which leads to changes in air pressure and wind patterns in northern latitudes, which very probably lead to colder temperatures and more severe winter storms across North America and northern Europe.