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Between intense cold and extreme heat: what if this was just the beginning?

Heat dome. | Posted on 2021-06-29 18:55

Waves of intense cold in winter, extreme heat in summer. What if this is just the beginning?

The various meteorological services tell us how polar cold waves hit North America in unprecedented proportions, reaching certain regions of the United States for the first time. Texas, Oregon, Louisiana, Mississippi, Kentucky, Ohio paralyzed by freezing cold with temperatures often 20 degrees below normal for the season!

They also know how to explain to us how, now, episodes of extreme heat are raging in many parts of the world.

What may be more complicated to explain, however, is why all these extreme phenomena occur. Obviously, we cannot help but, like a majority of the scientific community, to highlight global warming. Records of cold or heat have already been broken in the more or less distant past, but the violence with which these meteorological phenomena strike nowadays, is the major cause of concern for scientists. Their recurrence will certainly be proof of a profound disruption of the climate which can lead us to very difficult living conditions.

We have often mentioned the heat records broken summer after summer in the tundra or the Arctic. 2021 should not escape this new rule. No more in Russia than in many other countries, judging by the temperatures recorded over the last two days: 48 ° C in Russia, 46.6 ° C in Canada, 44 ° C in Portland in the Oregon and Seattle, 32 ° C at Saskylah in northern Russia.

While temperatures have flirted with 45 ° C in many cities in these regions, weather forecasts warn of the likelihood of many heat records falling again.

Never seen. More than 40 new temperature records were set in the province of British Columbia, western Canada, on Saturday June 26 and Sunday June 27. Lytton is now the town holds the absolute record heat in the country for keeping weather records 46.6 ° C. Hotter than Dubai. A little further south, in the northwest of the United States, records are falling into disarray, prompting the authorities to sound the alert: they fear that hospitals will be filled with victims of heatstroke and fear the departure of devastating forest fires.

At the origin of this furnace? A "heat dome" over the American Northwest.

This extreme weather phenomenon hits Oregon and Washington State, in the northwestern United States, and British Columbia, located in southwestern Canada. By touching the Pacific Northwest, this dome broke the heat record not only for Canada, but also for all the territories located above 50 degrees north latitude. The Canadian city of Lytton at 46.6 ° C is located at 50.2 degrees latitude.

“Since there is no precedent in local climate records for the events we are experiencing, it's a bit disconcerting to work without a point of comparison,” concedes a local forecaster . "The records are going to fall dramatically." For Jeff Berardelli, meteorologist and climate specialist for CBS , "this is the type of event that is only supposed to occur once every thousand years."

Specialists, used to sounding the alarm, seem to lack words to describe the situation. "I think I really have difficulty in making people understand the severity of this heat wave" , admitted the American climatologist Zack Labe, on Twitter, noting that there was no shade of purple capable, on the maps he uses, to report such temperatures. "I can't believe my eyes," British meteorologist Scott Duncan tweeted, referring to the "most frightening heat wave in history."

The previous week had already been marked by the creation of a heat dome over the American West. This time, it was the southwest of the United States that had lived in a furnace, the thermometer reaching 46.6 ° C in Las Vegas (Nevada). On June 17, the city of Palm Springs, built at the gates of the desert in southern California, had matched its record heat of 50.5 ° C - the city was still 49.4 ° C ten days later.

Quoted Friday by National Geographic , the weather program manager of the weather services for the western United States, Andrea Bair, estimated that the heat dome forming over the north was part of the " same high pressure pattern that we had here : it only moves north, south, west or east, getting stronger or weaker ". And to already announce that "the models predict that new episodes of heat will occur as we approach July 4".

Daily life overheating

"My children's schools are closed tomorrow due to the extreme heat. It had never happened in my life. The climate emergency is upon us ," tweeted Canadian researcher Seth Klein, an expert in policy on struggle. against global warming, based in Vancouver (Canada). Nearby, in Pemberton, also in British Columbia, authorities ordered the evacuation of neighborhoods , fearing that the rapid melting of the mountain ice could cause the river to suddenly overflow.

In the region, stores are out of stock of air conditioners and fans, while cities have opened cooling centers and vaccination campaigns against Covid-19 have been canceled. Electricity consumption in British Columbia has hit record highs as locals try to cool off. Unlike California homes, few families have air conditioning. In the vicinity of Portland, Oregon, the power grid broke, leaving thousands of people without power on Sunday. In Seattle, Washington, the heat melted the asphalt , forcing authorities to close several roads.

But with peaks of 45 ° C in the shade, it is still the human body that suffers the most, in this region where seasonal temperatures traditionally hover around 24 ° C in June, reports The Verge . Thus, the last events of the US Olympic athletics selections, which take place in Eugene, Oregon, were suspended Sunday due to the extreme heat: difficult to hold such a competition in 41 ° C.

A well-known phenomenon that can be observed all over the world

At the origin of these extreme temperatures is a well-known phenomenon: the northward rise " of a very hot air mass arriving from Mexico, to which are added high pressure conditions which favor what is called de subsidence, " Frédéric Nathan, forecaster at Météo France, told franceinfo. "Subsidence is the fact that a wind blowing vertically comes to compress the air mass." However, by crashing onto the ground, the mass of hot air further increases its temperature. "It's a bit like the phenomenon we have in a bicycle pump, continues Frédéric Nathan. When you press hard on it, it heats the air: it's compression."

"Heat dome" is therefore the expression "to say that it is very hot and that the high pressure conditions press the hot air on the ground, promoting even more heat" , summarizes the forecaster.

If a heat dome has settled in western North America, the conditions that gave rise to it can occur anywhere in the world, notes Frédéric Nathan. On Twitter, climatologist Christophe Cassou points out that "omega circulations" - the articulation of depressions and an anticyclone, here taking the form of the Greek letter - " also occur in the west of the Europe". "Are France and Europe more broadly ready to suffer such a blow from the point of view of health (lethal heat), agriculture and other major risks (fires, etc.)?" he asks ?

A phenomenon amplified by global warming

The creation of a heat dome is a phenomenon that can occur anywhere and has always been, notes Frédéric Nathan, of Météo France. It is even this phenomenon that had allowed the previous record recorded in Canada, in 1937: 45 ° C recorded in two weather stations in Saskatchewan, in the center-west of the country. On the other hand, "warm air masses today are generally warmer than they were fifty years ago. So when there is a somewhat extreme situation, like the one we are witnessing at the moment in Canada, we systematically break records, " he continues, indisputably pointing to " the impact of global warming ".

"What is new with global warming is the fact that, on a global scale, records for heat fall almost every day, while we increasingly rarely see records for cold, even if it still happens from time to time ", concludes the specialist.

Source : France Info.

Posted on 2021-06-29 18:55

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