A warming planet in a Northern snow field?
Although it is well documented that the earth’s frozen areas are in retreat, evidence of thinning Arctic sea ice does not even begin to explain why the world’s major Northern hemisphere cities are having colder winters.
Last June, during the International Polar Year conference, James Overland said that there are more cold and snowy winters to come. He argued that the exceptionally cold snowy 2009-2010 winter in Europe had a connection with the loss of sea-ice in the Arctic. The cold winters were associated with a persistent ‘blocking event’, bringing in cold air over Europe from the north and the east.
It is the way in which seasonal snow fall has continued to increase in the Northern climes, even as other frozen polar still areas are shrinking that baffles people about climate warming.
But the real story of the current snowmaggedon, snowicane, snowpocalypse or simple snow storm, lies elsewhere…
Because in the past two decades, snow cover has expanded across the high latitudes of the Northern Hemisphere, especially in Siberia, just north of a series of exceptionally high mountain ranges, including the Himalayas, the Tien Shan, the Altai, the Alps and the Lower Rockies.
Still the high topography of Asia influences the atmosphere most and 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 three decades, much more moisture has become available to fall as snow over the continents.
So the snow cover across Siberia and the North, 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 Northern Europe.
This makes us gold.
Really cold as when in the moors of Norfolk we say that we get the Siberian chill.
Yours,
Pano
PS:
That is why the Eastern United States, Northern Europe and East Asia have experienced extraordinarily snowy and cold winters since the turn of this century.
Even though this decade has been the warmest decade on record and 2010 is slated to be the warmest year on record… in a hundred years of warming.
Still the winter snow feels really cold and sharp. When you walk around London for weeks on ice you cannot fail to notice that the weather has indeed changed.
Most weather forecasts have failed to predict these colder winters because the primary drivers in their models are the oceans.
Oceans, which have been warming even as winters have grown chillier…
PS2:
Now the long range forecasters, who have succeeded in predicting the snowmaggedon, have done so only because they have paid attention to the snow in Siberia.
PS3:
Still the evidence mounts.
Climate warming causes the cold snap in London, New York and Washington…
BTW Ask the Norfolk hunters if you don’t believe me.
