There has been an absolute flurry of research, news articles and blog posts over the past several weeks concerning what scientists are calling an unexpected consequence of global warming- some of the heaviest snowfalls on record across eastern North America. Scientists now believe that this phenomenon on domino effect in an interconnected series of warming-related changes that are occurring globally.
Briefly, the Arctic ice cap is melting at an alarming rate. This has already and will continue to produce an excess of moisture. Coupled with this is the warming of sea surfaces globally, which is causing more evaporation and moisture input to the atmosphere. This has resulted in a steady increase in snowfall across Siberia.
Snow changes the thermal properties of landscapes due to its high reflectivity. Just as we feel cooler in the summer if we’re outside in a white shirt, a snow covered meadow will absorb less incoming solar radiation, and produce a region of lower air temperatures. This effect known as the “albedo effect”, and it has been leading to abnormally low winter temperatures in Siberia despite globally warmer winters.
The jet stream refers to a “virtual river” of 100-250 mph winds that circle the earth at mid-latitudes. It is known to be a dominant force controlling global weather patterns. As the jet stream pushes across Siberia, it is now encountering a colder dome of air. This causes its waves of air to scatter and for its west-east trajectory to become more erratic. In particular, waves of air are now being deflected north and then south, causing cold Arctic air to push south over eastern North America.
In December 2009, northern hemisphere snow cover was the second largest extent on record. North American snow cover was the largest extent ever recorded.
I won’t go any more into the details of this discussion here, but I’ll point you to a few articles that do a good job summarizing the science:
–This is a recent New York Times article by Judah Cohen, director of seasonal forecasting at environmental research agency
–By Robert Conners, environmental journalist
— A special report by the National Science Foundation on temperature anomaly predictions for North America
Happy 2011, stay warm!!