When climate change sends us a shot of cold

Quand le changement climatique nous envoie un coup de froid

Photo: Annik MH de Carufel Le Devoir
In the next few years, while the rest of the world will continue to break heat records, the North-east of North America, he will continue to have (very) cold.

While another shot of cold is preparing to fall on a part of the North America, a reminder : it is not only predictable in the context of global warming, but it is also possible that, in the next few years, while the rest of the world will continue to break heat records, the North-east of North America, he will continue to have (very) cold.

The culprit : the jet stream a polar, known by its English name of jet stream. It is a powerful air corridor, a “ribbon” winds up to 300 km/h, which “encloses” the cold air where it is supposed to be locked up : above the Arctic. It is at its strongest in winter, when the temperature differences between its north and south sides are the greatest. Result, when the jet stream weakens, the cold air — what we call the polar vortex — descends further south than usual. This is what we witnessed earlier this month in the American east, and the risk of review this week. Temperatures and snowfall which Quebecers are accustomed to are likely to hit a good portion of the interior of the continent.

As the jet stream weakens at irregular intervals is not, in itself, abnormal. The whole question is rather to know if the jet stream weakens, more frequently as the Arctic warms. This is the hypothesis put forward by several leading climate scientists, and it has all the more weight that the Arctic is warming faster than the rest of the planet, thus increasing the risk that the jet stream is disrupted.

In the meantime, as the “victims” of a polar vortex had already noted, it has another characteristic : its duration. Once the barrier of the jet stream has left to escape the cold air — which, this winter, occurred around New Year — it often takes days, or even weeks, to bring it back to its starting point. In other words, temperatures below normal the first half of January could come back to haunt North Americans until February.

During this time the other side of the planet, Australia’s record heat : on the 24th of January, at least 28 meteorological stations have registered record temperatures of over 35 degrees. One of them, in Adelaide, showing a peak of 46.6 degrees, while the city of Port Augusta announced 49,5 degrees. If the trend of the past two weeks continues, this will be there in the summer the warmest since over a century that such measures exist.

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