Human-caused climate change has made drought in the Northern Hemisphere this summer "at least 20 times more likely", scientists warn.
A continuation of warming would make these episodes more intense and more frequent, add these researchers from the World Weather Attribution (WWA), a network of pioneering experts in the attribution of extreme events to climate change, which publish a study this Wednesday.
The summer drought has affected many European countries, starting with France, with dry rivers and restrictions in some localities.
Parts of the United States or China were also affected.
The consequences were felt in the agricultural sector, with declining harvests and possible effects on already high inflation.
This situation has also favored forest fires and disrupted the production of electricity, particularly hydraulic and nuclear.
Experts from the European Commission's Joint Research Center had estimated this summer that the drought was "the worst for at least 500 years".
Such a drought of the soil, which has affected Europe, China or the United States, is likely to occur approximately every twenty years with the current climate, against approximately every 400 years or even less often without warming, according to the WWA scientists.
True influence of human activities 'probably higher'
In the northern hemisphere (outside the tropics), human-induced climate change has made drought "much more likely", say researchers from the WWA network, who work in prestigious institutions in Europe, the United States and in New Zealand.
Da,s detail, this probability was increased by a factor of "at least 20" for the lack of soil moisture in the root zone, the part of the soil corresponding to 1 m underground and where the plants extract the water for food.
It is when this very important area is affected that we speak of “agricultural” or “ecological” drought.
The probability of the event was increased by a factor of "at least 5" for surface soil moisture, which is only the top seven centimeters.
"But as is usually the case for quantities that are difficult to observe, the exact figures are uncertain," warn the authors.
"The estimates of the influence of climate change in the study are conservative: the true influence of human activities is probably higher," said the WWA.
“We need to stop burning fossil fuels”
Warming since the start of the industrial era, which has been fueled by fossil fuels, has already reached almost 1.2°C, leading to a series of disasters.
The Paris agreement aims to keep this warming below 2° and if possible close to 1.5°.
"The summer of 2022 has shown how human-caused climate change is increasing the risk of agricultural and ecological droughts in agricultural and densely populated regions of the northern hemisphere," said Sonia Seneviratne, a professor in Zurich, who co-authored the study.
“We need to stop burning fossil fuels if we want to stabilize climatic conditions and prevent these droughts from getting worse.
They will become more frequent and intense with any increase in warming,” she warned.
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The researchers also looked at the region of Central and Western Europe alone.
The results are less spectacular: global warming linked to human activity has made surface drought about 5 to 6 times more likely there and agricultural drought about 3 to 4 times more likely, according to their calculations.
This difference does not mean that climate change has had a lesser impact on Europe compared to the rest of the northern hemisphere, but rather reflects the methodological ease of better understanding events over a larger region.
“Usually you get stronger climate change signals over larger regions,” said Friederike Otto of Imperial College London, co-author of the study, in a presentation to journalists.
"When you look at smaller regions, you find more daily weather variability in the data," while that effect is "mitigate" by considering larger areas, she explained. .
