The Frozen Why’s and Wherefore’s

“Cold enough for you?” I know: a trite thing to say. Everyone knows already that it’s cold: Europe, North America, Asia. Better if someone could tell us why, and what we can do about it!

Comes now Pierre Le Hir, writing in Le Monde, with a bit of explanation (Why the Northern Hemisphere suffers under cold waves). According to his account, this winter’s extraordinary cold is the product of one key variable, together with another aggravating factor. That variable is NAO, or North Atlantic oscillation, which is the weather-pattern determined by the intensities of the low-pressure center usually somewhere around Iceland and the high-pressure center usually around the Azores. If NAO is positive, then winds coming into Europe carrying warmth stored by the Atlantic are strong, resulting in a mild winter; if it’s negative, they are weak, resulting in cold.

Naturally, right now NAO is negative. Then there is that aggravating factor, of which you have heard before: El Niño, defined as abnormally-high surface-water temperatures in the Pacific. Starting from last summer the El Niño phenomenon has been elsewhere than where it usually is found (more mid-Pacific than near to the South American coast). This helps to make things yet colder in the Northern Hemisphere, particularly in North America. In fact, author Le Hir reports that the weather establishment still does not regard the cold experienced so far this winter in Europe to be particularly outside of the realm of expectation – for all of the deaths (22 in the UK) and various disruptions to transport in France and some other countries that the article goes on to list.

Oh, and as to that second point: We can’t do anything about it.

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