Climate change deniers have been in a lather telling us that the severe cold snaps in North America provide undisputed evidence that global warming is, in the words of some, a load of crap. The North American weather is certainly the major talking point but apart from the deniers telling us that it is simply because global warming doesn’t exist, nobody has bothered to explain what has actually caused this unprecedented weather pattern.

Somebody apparently has, or did, a couple of days ago, but it has conveniently escaped the major news networks. The explanation by Eric Holthaus in the online Quartz magazine under the article titled ‘How global warming can make cold snaps even worse‘ (which will make a lot of sense to anyone who has seen the 2004 movie ‘The day after tomorrow‘) is worth repeating. Below is a condensed excerpt of the article:

Global warming is probably contributing to the record cold, as counter-intuitive as that may seem. The key factor is a feedback mechanism of climate change known as Arctic amplification. Here’s how to explain the nuts and bolts of it to your under-informed family and friends:

Snow and ice are disappearing from the Arctic region at unprecedented rates, leaving behind relatively warmer open water, which is much less reflective to incoming sunlight than ice. That, among other factors, is causing the northern polar region of our planet to warm at a faster rate than the rest of the northern hemisphere. (And, just to state the obvious, global warming describes a global trend toward warmer temperatures, which doesn’t preclude occasional cold-weather extremes.)

Since the difference in temperature between the Arctic and the mid-latitudes helps drive the jet stream (which, in turn, drives most US weather patterns), if that temperature difference decreases, it stands to reason that the jet stream’s winds will slow down. Why does this matter?

Well, atmospheric theory predicts that a slower jet stream will produce wavier and more sluggish weather patterns, in turn leading to more frequent extreme weather. And, turns out, that’s exactly what we’ve been seeing in recent years. Superstorm Sandy’s uncharacteristic left hook into the New Jersey coast in 2012 was one such example of an extremely anomalous jet stream blocking pattern.

When these exceptionally wavy jet stream patterns occur mid-winter, it’s a recipe for cold air to get sucked southwards. This week, that’s happening in spectacular fashion.

Climate scientist Jennifer A. Francis of Rutgers University explains this process in a short video (h/t Climate Progress):

This effect has already been measured with mid-level atmospheric winds in the northern hemisphere decreasing by around 10% since 1990. Not-so-coincidentally, that’s about the same time when Arctic sea ice extent really started to crash.

That all makes sense to me (but I’ve also seen the movie).

And news.com.au – of all places – give us a bit of a hint that the above is more than likely plausible after all. In telling us the other day that Canada is colder than Mars they also tell us, without the spectacular headlines, that:

The North Pole was also 10 degrees warmer than Winnipeg.

Interesting, isn’t it?