Catastrophic floods such as the one that hit Europe recently could become much more frequent due to global warming, researchers say.
High-resolution computer models suggest slow storms could become 14 times more frequent on earth by the turn of the century in the worst-case scenario. The slower a storm moves, the more rain it pours over a small area and the greater the risk of severe flooding.
Researchers already knew that the higher air temperatures caused by the climate crisis mean the atmosphere can hold more moisture, which in turn has led to more extreme downpours. The latest analysis, however, is the first to assess the role of slow thunderstorms in extreme downpours in Europe.
The storms projected in the new study are moving even slower than those that inundated Germany, the Netherlands and other countries last week and thus would result in even more extreme rainfall and flooding. “The simulations give the idea that even worse can happen,” said Abdullah Kahraman of Newcastle University in the UK, who led the research.
Professor Lizzie Kendon of the UK Met Office said: “This study shows that in addition to the intensification of precipitation with global warming, we can also expect a large increase in slow storms. This is very relevant for the recent floods observed in Germany and Belgium, which highlight the devastating effects of slow storms. “
Scientists believe the rapid warming of the Arctic may be causing weather systems to slow down, slowing high-altitude winds such as the jet stream. The phenomenon has already been linked to the devastating heat waves in Russia and the floods in Pakistan.
The study showed that the greatest increase in slow storms over land was in summer. “In summer, especially in August, the greatest increase occurs over much of the European continent,” Kahraman said.
He was surprised that the modeled impact spread to the colder regions of northern Europe: “We have found that all of Europe, including the UK and Scandinavia, has potential. very slow extreme rain, ”he said.
The intensity and scale of recent flooding in Western Europe, in which more than 180 people died, shocked climatologists, who did not expect the records to be so widely broken over such a large area or so early.
German Chancellor Angela Merkel visited one of the worst affected regions on Sunday and said: “We must step up the fight against climate change”. Many climatologists have said that global warming is making extreme weather events more frequent and intense.
The study, published in the journal Geophysical Research Letters, used Met Office computer models with a resolution of 2 km, the same as that used in short-term weather forecasts. Scientists have evaluated the evolution of slow storms in a scenario where carbon emissions are not reduced and continue to increase.
“It gives us a very useful idea of how the climate can change if people don’t really change in terms of emissions or behavior, so I think it’s useful in that sense,” Kahraman said.
The analysis is one of the first to model the climate of the whole of Europe at such a small resolution. The team hopes to look at slow storms in other scenarios where emissions will be reduced in the future, but expects the increase in the frequency of these storms to persist.
“Governments around the world have been too slow to reduce greenhouse gas emissions and global warming continues at a steady rate,” said Professor Hayley Fowler, also at Newcastle University and a member of the study team.
“This study suggests that changes to extreme storms will be significant and lead to an increase in the frequency of devastating floods across Europe. This, along with the current floods in Europe, is the red flag we need to produce improved warning and emergency management systems. “