Global warming has increased the likelihood and intensity of the floods that ravaged Germany and Belgium in July, claiming more than 200 lives and billions of euros in damage, according to a study released on Tuesday.
The occurrence of such an extreme episode in these regions has been made up to nine times more likely by human-induced warming, with at least 20% more probability.
Climate change has also "increased the amount of rain over a day by between 3% and 19%," according to scientists from the World Weather Attribution (WWA), which brings together experts from various research institutes around the world.
This is the second study to clearly point to warming in the natural disasters that have multiplied this summer.
The WWA had previously calculated that the "heat dome" that suffocated Canada and the American West at the end of June would have been "almost impossible" without the effects of climate change.
In early August, the UN climate experts (IPCC) had also sounded the alarm in a shock report, pointing to global warming even faster and stronger than feared, threatening humanity with disasters. " unprecedented ".
The threshold of + 1.5 ° C - an ideal target not to be exceeded according to the Paris agreement - could thus be reached around 2030, i.e. 10 years earlier than estimated.
The devastating effects - droughts, fires or floods - are already being felt around the world.
On July 14 and 15, heavy flooding caused by torrential rains had killed at least 190 people in Germany and 38 in Belgium.
Read also Floods in Germany: ten edifying photos of the disaster
Germany will have to devote 30 billion euros to the reconstruction of disaster areas and the disaster has placed the issue of the climate emergency at the center of public debate, a few weeks away from decisive elections at the end of September for the succession of the Chancellor Angela Merkel.
Precipitation records largely broken
For the 39 international scientists gathered under the banner of WWA, there is no doubt: "Climate change has increased the probability, but also the intensity" of the events of July, underlined during an online presentation Frank Kreienkamp, of the service. German meteorologist, who piloted the study.
The episode "largely broke historically recorded precipitation records" in the affected areas, the researchers said.
The increase in precipitation is an expected consequence of warming, since a physical phenomenon increases the humidity of the atmosphere by about 7% for each additional degree.
The authors ran different models to estimate how warming affected the maximum amount of precipitation over a period of one or two days in the worst affected regions, the Ahr and Erft river basins in Germany and the Meuse valley. in Belgium.
But also over a larger region covering these two countries, as well as the neighboring Netherlands, affected to a lesser extent.
They observed a "tendency to strengthen", although there is still "great variability" from year to year. And evaluated the probability of occurrence in Western Europe of an episode like that of July at once every 400 years. In other words, a one in 400 chance each year that such a disaster will occur. And they "will become even more common" if the warming continues, the study said.