Barely a week after a severe heat wave hit British Columbia in western Canada and across the northwestern United States, 27 scientists from major climate research organizations (including Princeton, Columbia, Cornell, Berkeley and Washington University in the United States, among others, British Columbia in Canada, the Royal Meteorological Institute of the Netherlands, Oxford for the United Kingdom, Pierre-Simon Laplace Institute for France) “Rapid analysis” of the link between this extreme meteorology on the site of the “World Weather Attribution” program do publish. Event and current climate change. Their conclusion is clear: an episode like this would not have been so intense without a 1.2 °C increase in global temperature since the start of the industrial era.
Beginning June 27, the west coast of Canada and the northwestern United States experienced extreme heat that the region had never experienced in living memory. A record 49.6 °C was recorded at the foot of the Rocky Mountain range on June 29. This is about 5 °C higher than the previous Canadian record of 45 °C recorded in 1937. According to Météo France, it is also an absolute record for a station located above 50 degrees north latitude. Values observed elsewhere in British Columbia are 40 °C, 20 °C above the mean seasonal temperature, and above the symbolic threshold for North Americans of 100 °F (38 °C). This phenomenon is due to the coincidence of two different events. The rising heat from Mexico was blocked by a powerful high pressure system, keeping a bubble of hot air at great height. A “heat dome” formed, which for several days diverted the sediments from the Pacific to the North Pole.
an extraordinary weather phenomenon due to its intensity
This series of meteorological events is not exceptional. Its intensity itself raises questions on researchers. They obtained measurements very quickly from stations located between 45 and 52 degrees north latitude in the vicinity of the cities of Vancouver, Seattle and Portland. He compared this data to his numerical model to compare the climate as it is with the 1.2 °C added by human activity since the beginning of 1919.I century and the climate of the past.
The study area and measurement station (the redder the dot, the higher the temperature) were selected to study the multiplication of Canadian heatwaves to climate change. Copyright World Weather Attribution
The recorded extreme temperatures far exceeded the average range observed in previous centuries, making any comparison difficult. But the researchers came to the conclusion that without the recent rise in temperature, such a heat wave would not have been possible at these latitudes. According to the most realistic statistical estimates, such temperatures may occur only once every 1,000 years in the early 21s.I century.
fear of crossing the irreversible threshold
According to the researchers, there are two possible reasons for this phenomenon. The first, the most reassuring one, is that it is an episode that has little chance of occurring and can be compared to a series of “misfortunes” in a succession of phases caused by this extraordinary heat wave. from global warming. The second – more worrisome – is that interactions within the climate system cause us to exceed irreversible boundaries that increase the likelihood of events that are beginning to be observed. Researchers recognize this: they must explore this second possibility to obtain certainty.
According to this hypothesis, a heat wave of this magnitude would be 150 times rarer in a climate warmer than 1.2 °C. In addition, the temperature recorded in June 2021 would have been 2 °C lower than at the start of the industrial era. And if we look to the future, a world with a 2°C increase, according to the limit set by the Paris Agreement, which can be met in 2040, such heat waves will return every five to ten years. France experienced a similar phenomenon in 2003. So this extraordinary heat wave can be repeated up to twice in a decade.