Longer and more frequent heat waves

Worldwide, since the 1980s, their movements have on average been less rapid – which partly explains why they last longer in a given region: on average 12 days instead of 8. They are also, on average, more frequent: 98 days in the year. Between 2016 and 2020, compared to 75 annually between 1979 and 1983.

These are the numbers that emerge from compiling all the heatwaves that occurred around the world between 1979 and 2020. Published on March 29 In the magazine Advancement of science. A “heatwave” is defined here as temperatures exceeding 95% of the 1981-2010 temperature, over an area of ​​at least 1 million square kilometres, for at least three days.

The “speed of travel” we are talking about has risen from 340 kilometers per day in the early 1980s to 280 kilometers per day – which is the factor that explains why the same region must endure a heatwave for longer. With known public health effects: The respiratory and heart problems associated with extreme heat are already well-studied, but they are They are amplified by heat which stays put longer.

A similar finding about displacement has been observed in other research on hurricanes: although researchers still disagree on whether or not there will be more hurricanes due to global warming, This other study concluded recently Hurricanes were moving more slowly than they were 40 years ago. Which could have the effect, again, of more damage above the unlucky area.

As for the study of heat waves, it shows that most analyzes of this type observed the extent or development of heat waves in one region at a time. By providing a global view of this development and movement, researchers in China and the United States hope to provide tools to adapt and perhaps mitigate future heat waves.