Hotter, more often, earlier and later. The multiplication of heat waves such as those currently affecting much of Western Europe or those that hit India in March-April is an undeniable sign of climate change, the scientists explain.
Globally, the years since 2015 are the warmest on record. And punctual heat waves are multiplying all over the world, with their trove of catastrophic effects, droughts, fires and of course loss of life.
More frequent and hotter heat waves
“Every heat wave we’re experiencing has been made hotter and more frequent as a result of human-induced climate change”summarizes Friederike Otto, of the Grantham Institute at Imperial College London.
“It’s pure physics: we know how molecules of greenhouse gases behave, we know that there are more of them in the atmosphere, that the atmosphere is warming, which means we expect more frequent and hotter heat waves and less frequent and milder cold. understands”explains during an online briefing that this specialist in “attribution” from extreme events to climate change.
This growing branch of climate science has calculated that the heat wave of unprecedented intensity and speed that hit India and Pakistan in March-April was 30 times more likely due to the changing climate.
Or that the extraordinary heat wave in Canada in June 2021, which killed more than 500 people at temperatures close to 50°C, would have been “almost impossible” without climate change. Or that warming to 3°C had added to the very strong summer heat wave in Europe in 2019.
“The increase in frequency, duration and intensity of these (heatwave) events in recent decades is clearly related to observed global warming and can be attributed to human activity”was featured abundantly in the World Weather Organization on Monday, July 18, commenting on the extreme heat in Western Europe.
The worst is yet to come
And it’s not over. According to UN climate experts, extreme heat waves would have 4.1 times more “chances” to intervene at +1.5°C average global warming compared to the pre-industrial era, the most ambitious target of the Paris Agreement of 2015.
It would be 5.6 times more likely at +2°C and 9.4 times more likely at +4°C. For even more intense and rarer heat peaks, the numbers rise to 8.6 times more at +1.5°C, 13.9 times at +2°C and… 39.2 times at +4°C!
However, the planet has warmed by nearly 1.2°C since the industrial revolution and according to the UN, current commitments by states, if fulfilled, would lead to global warming. “catastrophic” +2.7°C.
The climatic cycle has already changed profoundly, as Matthieu Sorel, climatologist at Météo-France, points out, who notes that the heat waves increasing in the country – already two this year – would be 1.5°C less intense at 3°C. C without the effect of climate change. “We are moving towards increasingly hot summers, where 35°C will become the norm and 40°C will be regularly reached.”
Humans will be increasingly affected by this heat, which can be deadly: 14% of people would be exposed to the effects of global warming at +1.5°C at least once every five years, but 37 % at +2°C, according to the IPCC.
Gold, “Everywhere in the world where we have data, there is an increased risk of death if we are exposed to high temperatures. (…) And the more extreme these temperatures become, the greater the risk”warns Eunice Lo, of the Cabot Institute for the Environment at the University of Bristol.
And “It is not only vulnerable people who risk health effects, even fit and healthy people are at risk”emphasizes the specialist.
Until you can die, especially from the effect of “wet thermometer”when the humidity in the hot air prevents the body from perspiring and thus dissipating its own heat.
The impacts are also devastating to the environment, with heatwaves amplifying droughts and fostering fires such as those currently ravaging France, Portugal, Spain, Greece and Morocco.
They can also threaten human food. India, the world’s second largest wheat producer, has been hit by the heat wave and has imposed a temporary embargo on the export of this grain, exacerbating the crisis caused by the Russian invasion of Ukraine.