NOAA recently declared this winter to be the 4th warmest on record for the contiguous United States. That sort of announcement might be expected in a warming world. But what about the relatively cold winters of 2009-2010 and 2010-2011, which featured historic blizzards in the Midwest and the East Coast? Florida had snow seven times in 2010! And while we Americans enjoyed a very mild winter this year, Europe endured its most frigid cold snap in decades. That sort of winter weather may seem counter-intuitive in a warming world; it’s the sort of weather columnist Thomas Freidman has in mind when he writes about “Global Weirding.”
Over the past few years, science has begun to demystify the weirdness in our winter weather, linking it directly to global warming. A paper published prior to the 2009-2010 blizzards found that changes in atmospheric circulations triggered by sea ice loss—a factor strongly connected to climate change—could also mean snowier winters in mid-latitudes. The lead author, Dr. James Overland, concluded that, “This can result in a warmer-than-average Arctic region and colder temperatures that may include severe winter weather events on the North American and European continents.”
More recent research provides further evidence that reduced Arctic sea ice cover generates wind patterns linked to heavy snowfall in North America, Europe and East Asia. Jiping Liu and coauthors concluded “that the recent decline of arctic sea ice has played a critical role in recent cold and snowy winters.”
|Normal jet stream configuration (Left). Jet stream configuration during the cold snap (Right)|
The jet stream separates cold air in the north from warmer air to the south. Normally, relatively gentle bends in the jet cause warmer or cooler than normal weather. However, the circulation changes linked to the reduction of sea ice increases the risk of a more meandering jet stream in mid-latitudes; a southward meander of the jet brings frigid arctic air with it, resulting in cold surges. This increasing tendency of the jet stream to meander means an increased risk of frigid temperatures and snowstorms in areas where most Americans and Europeans live. Meanwhile, this same meandering jet stream allows warmer air into the Arctic, which can further contribute to sea ice melt, reinforcing the cycle.
This dynamic is consistent with the cold snaps and blizzards of the past few years, most of which have been associated with perturbed jet flow. In other words, the past winter’s unusually cold temperatures in Europe and Alaska, as well as cold waves in recent years in the continental U.S., are indeed the types of events that we can expect to see more of in a warming world.
This recent science provides more evidence that global warming can alter the climate in ways that we don’t expect—global weirding. From cold snaps to droughts and extreme rainfall, climate change is influencing a multitude of weather events all over the globe, resulting in more weather at both extremes. Last year’s record snowpacks in the Western U.S. gave way to record snowpack deficits this year and the recent yearlong drought in Texas was punctuated by massive floods just north and east along the Mississippi and Missouri Rivers. The string of blizzards along the east coast, from 2009’s Snowpocalypse through the blizzards of January 2011, was a historic run of storminess, but since then there has been nary a flake to be found. Meanwhile, Europe experienced a historic cold snap coupled with abnormally heavy and widespread snow this winter. In Asia, heavy snow and avalanches have buried towns and the coldest weather in years caused the price of heating fuels to spike. This cold snap was in sharp contrast to heat waves in recent summers, some of which broke all time records in 12 Asian countries.
In the future we must prepare for more “weird” weather events, especially since studies suggest that as the arctic continues to melt, its influence on weather patterns here at home will grow. It has already changed wind patterns and as they continue to change, we’ll find out how weird the weather can really get.
Dan Huber is a Science & Policy Fellow at C2ES.