Europe’s Extreme Floods Are ‘Up to Nine Times More Likely’ Because of Climate Change

July’s heavy rains were made more severe by human-caused warming

Destroyed houses, roads and a bridge pictured during ongoing cleanup efforts in the Ahr Valley region following catastrophic flash floods on August 04, 2021 in Rech, Germany.
A town along the Ahr river was damaged following intense flooding. Photo by Thomas Lohnes/Getty Images

The extreme rainfall that devastated parts of Europe last month was made more likely and more severe by climate change, according to a new report. The downpours, which swept through Germany and Belgium in July, were 3 to 19 percent more intense and 1.2 to 9 times more likely because of human-caused warming.

"It is difficult to analyze the climate change influence on heavy rainfall at very local levels, but we were able to show that, in Western Europe, greenhouse gas emissions have made events like these more likely," says study co-author Sjoukje Philip to Matt McGrath for BBC.

The rainfall that swept through the area from July 12 to July 15 killed more than 200 hundred people and forced thousands to flee from their homes. Communities around the Ahr and Erft rivers in Germany and in the Meuse region of Belgium received between 5 to 7 inches of rain per day, according to the Washington Post’s Jason Samenow. Some areas in the region got as much rain in the span of a few days as they expected in an entire year.

"Extreme weather is deadly," says study co-author Friederike Otto, a University of Oxford climatologist, to Reuters. She has family that lives in some of the impacted areas, adding, “For me, it was very close to home."

Otto and other climate scientists at the World Weather Attribution (WWA) project were curious how much human-induced climate change altered the likelihood and intensity of July’s heavy rains. Using local weather records and climate models, the team analyzed the areas hit hardest by the recent floods: France, Germany, Belgium, the Netherlands, Luxembourg, and Switzerland. Then, they compared weather records to a model of a world without human-caused warming—onw 1.2 degrees Celsius cooler than our own. Researchers found that climate change made severe flood events 1.2 to 9 times more likely, and 3 to 19 percent more severe. The team says their broad range is due to limited historical records and damage caused to monitoring systems during the floods.

“This event demonstrates once again in 2021 that extremes breaking observed records by far, exacerbated by climate change, can strike anywhere, induce huge damages and cause fatalities,” says study co-author Frank Kreienkamp, a climate scientist with the German Meteorological Service, to David Vetter for Forbes.

Part of the reason climate change means more rainfall is because a warmer atmosphere can hold more moisture. Rising temperatures can also slow down weather systems, causing them to linger for longer. A recent report from the United Nations Intergovernmental Panel on Climate Change (IPCC) predicts more severe rains and flooding worldwide, and this pattern is likely playing out in other regions across the globe.

Otto says we should prepare for flash floods like those in July, which should be a once-in-400-year event, to become more frequent.

"We will definitely get more of this in a warming climate,” says Otto to Reuters. "These floods have shown us that even developed countries are not safe from severe impacts of extreme weather that we have seen and known to get worse with climate change. This is an urgent global challenge and we need to step up to it. The science is clear and has been for years."