If you've caught yourself donning your shorts recently, you've noticed it's been a bizarrely mild winter for most Americans. As the AP reports, snowfall in parts of the country accustomed to wintry weather is nowhere near seasonal average. Bismarck, N.D., has seen one-fifth its normal snow, while Buffalo is three feet below average. Then there's Midland, Texas, which has seen more snow this season than Minneapolis or Chicago.
The culprit, as Kim Mackrael writes in The Globe and the Mail, is a volatile weather pattern called the Arctic oscillation. When the oscillation value is negative the jet stream loosens, allowing pockets of icy Arctic air to travel south. When it's positive, as it has been this winter, it results in 70 degree January days in Washington D.C..
But not all of the hemisphere is sunbathing and playing golf. Wide swaths of Asia have been blanketed by snow. Earlier this month, record snowfalls in Anchorage, Alaska, left drifts so heavy that they sank fishing boats. In Eastern Europe, where temperatures have plummetted to -30 Celsius, blizzards and deep freeze have left 123 people dead and more than 11,000 villagers trapped by heavy snow in Serbia's mountains.
Why this winter's double standard? According to Mike Halpert, Deputy Director of the National Weather Service's Climate Prediction Center, it's because of the way the Arctic oscillation is interacting with another weather phenomenon: the North Atlantic oscillation. As he says to the AP, about 90 percent of the time, the North Atlantic and Arctic oscillations are in synch. This winter, for some reason, the Arctic jet stream escaped into Europe and Asia while staying tightly sealed over North America.
Opponents of climate change like to use any aberrant winter weather as an argument against a warming planet. The reality is that the planet's climate systems is an intricate system of moving parts. Changes aren't uniform; for example, this year's snowfall numbers are actually comparable to seasonal averages, except nearly all of that snowfall was in Europe and Asia, which saw its ninth snowiest January since 1966. There's still a lot we don't know about climate change, but we do know that it's changing. Back in the fall, a Pennsylvania-based weather tracking company predicted that this would be one of the coldest winters on record for North Americans. They were right, just on the wrong side of the planet.