The Weather Outside is Frightful

OK, maybe not so much here in southern New Mexico, though I suppose you could get a sunburn if you left your shirt off too long outside - but Europe is having its third tough winter in a row and the eastern US is also in the fridge again. So what does it mean? Proof of global warming or disproof (I couldn't bring myself to say "a refudiation", but I was tempted).

Judah Cohen, a commercial weather forecaster, offers a interesting meteorological theory in the NYT.

Annual cycles like El Niño/Southern Oscillation, solar variability and global ocean currents cannot account for recent winter cooling. And though it is well documented that the earth’s frozen areas are in retreat, evidence of thinning Arctic sea ice does not explain why the world’s major cities are having colder winters.

But one phenomenon that may be significant is the way in which seasonal snow cover has continued to increase even as other frozen areas are shrinking. 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 and the Altai.

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.

As always, for the details you need to read the article, but the argument is that less artic ice cover puts more moisture and hence snow cover in Siberia and that steers the jet stream differently than it was formerly. It sounds plausible, but I wonder how it runs in the weather and climate models. Doubtless we shall learn more over the next decade or so. Meanwhile, you might consider: is a snow blower really a luxury purchase - though it will increase your carbon footprint.