The heat wave that hit western North America last year was, statistically speaking, one of the most intense on record anywhere in the world, according to a study released Wednesday.
At the end of June 2021, a “heat dome” of extremely rare intensity pushed the mercury to temperatures never seen in Canada. In Lytton, a village that has become symbolic of the climate crisis, the temperature approached 50°C, before the municipality was completely razed by flames.
British researchers now confirm that this heat wave is, relative to the climatology of the affected region, one of the six most extreme events to have occurred on the planet since 1960.
To reach these conclusions, the scientists first analyzed the distribution of temperatures during the three hottest months of the year in a region encompassing southwestern British Columbia and parts of the states of Washington and Oregon.
They later found that the regional maximum (39.5°C) on June 29, 2021 was well above the average for the past decade (23.4°C). Specifically, it was within 3.6 standard deviations of the mean. (Standard deviation is a measure of the typical spread of a data distribution.)
Applying the same methodology to the entire planet, they found only five other heat waves that were equally out of the ordinary. Of the eight most extreme events, four occurred in North America, and three in the last three years (in Alaska in 2019, in Brazil in 2020 and in Canada in 2021).
“Extremes of heat are a natural part of our climate system, but they are getting hotter and longer due to human-induced climate change,” writes Vikki Thompson, from the University of Bristol, author of this published article. in Science Advances with a handful of colleagues.
Increasingly extreme heat waves?
The scientists answer another question in their paper: will heat waves become more and more extreme compared to the average temperature, which will increase by a few degrees by the end of the century?
The answer is somewhat reassuring: according to them, heat waves will not be more exceptional, compared to the climatology of the last decade, than they are now. Their intensity will follow the increase in temperature, but nothing more.
“Our results confirm the conclusions of the Intergovernmental Panel on Climate Change (IPCC) that there are changes in the extremes, but that these shifts in extreme temperatures can be explained by a shift in the average” , they point out.
Nevertheless, the average moves quickly. If the worst-case scenarios for greenhouse gas emissions materialize, in British Columbia, a heat wave such as that of 2021 will occur every six years by 2080.