At the same time, the World Meteorological Organization has just released a report showing that 2010 will be among the three warmest years on record - possibly the warmest on record. Moreover, the decade ending with 2010 will be the warmest decade on record.
How does one resolve the seeming dichotomy between the fact of four foot snow drifts and the fact that the world will be setting a record for heat this year? According to Judah Cohen, writing today in The New York Times, it is all due to the topography of Asia.
The high topography of Asia influences the atmosphere in profound ways. The jet stream, a river of fast-flowing air five to seven miles above sea level, bends around Asia’s mountains in a wavelike pattern, much as water in a stream flows around a rock or boulder. The energy from these atmospheric waves, like the energy from a sound wave, propagates both horizontally and vertically.
As global temperatures have warmed and as Arctic sea ice has melted over the past two and a half decades, more moisture has become available to fall as snow over the continents. So the snow cover across Siberia in the fall has steadily increased.
The sun’s energy reflects off the bright white snow and escapes back out to space. As a result, the temperature cools. When snow cover is more abundant in Siberia, it creates an unusually large dome of cold air next to the mountains, and this amplifies the standing waves in the atmosphere, just as a bigger rock in a stream increases the size of the waves of water flowing by.
The increased wave energy in the air spreads both horizontally, around the Northern Hemisphere, and vertically, up into the stratosphere and down toward the earth’s surface. In response, the jet stream, instead of flowing predominantly west to east as usual, meanders more north and south. In winter, this change in flow sends warm air north from the subtropical oceans into Alaska and Greenland, but it also pushes cold air south from the Arctic on the east side of the Rockies. Meanwhile, across Eurasia, cold air from Siberia spills south into East Asia and even southwestward into Europe.
And so we get the Metrodome in Minneapolis collapsing under the weight of snow, people dying in Poland due to subzero temperatures, and New York shut down for days because of four foot snow drifts. Even here along the humid Gulf Coast, we are not totally immune. We had our first frosts in November, almost three weeks ahead of schedule this year.
But all of this cold weather is not a contradiction of global warming. It is, in fact, confirmation of it. If we don't begin to take steps to walk back our human influence on the climate, we can expect to experience even more severe extremes in weather - both hot and cold - in the future.