Deadly floods nine times likelier in warmer climate

The World Weather Attribution group studies the possible influence of climate change on extreme weather events.

The aftermath of the recent flood at Rech in the Ahr River region of Germany’s Rhineland-Palatinate state. Picture: AFP

Climate change has made extreme rainfall similar to the downpours that caused last month’s devastating floods in Germany and Belgium up to nine times more likely, a study has found.

More than 90mm of rain fell in a single day around the Ahr and Erft rivers in Germany, far more than previous records. The resulting floods killed at least 220 people.

Scientists calculated the role of climate change on the intense rainfall that caused the floods by analysing weather records and computer simulations to compare today’s climate, which is about 1.2C warmer on average globally than in pre-industrial times, with the climate of the past.

They found that climate change had made such intense rainfall between 1.2 and 9 times more likely to happen and had also increased the amount of rain that fell in one day by between 3 per cent and 19 per cent.

They said similar events could be expected to hit any part of western Europe from the north of the Alps to The Netherlands about once in 400 years in the present climate, meaning that several such events were likely across the wider region over that timeframe. The scientists analysed rainfall rather than river levels partly because some measurement stations were destroyed by the floods.

The results reinforce the conclusions of this month’s report by the Intergovernmental Panel on Climate Change, which said there is unequivocal evidence that humans are warming the planet, and that human-caused climate change is the main driver of changes in weather extremes. The report found that as temperatures rise, western and central Europe will be exposed to more extreme rainfall and flooding.

The study of last month’s flooding was conducted by the World Weather Attribution group, which studies the possible influence of climate change on extreme weather events such as storms, extreme rainfall, heatwaves, cold spells and droughts.

It includes scientists from the University of Oxford, the Met Office and universities and meteorological agencies in Belgium, France, Germany, Luxembourg, the Netherlands and the US.

Friederike Otto, an author from the Environmental Change Institute at the University of Oxford, said: “These floods have shown us that even developed countries are not safe from severe impacts of extreme weather that we have seen and (know will) get worse with climate change. This is an urgent global challenge”.

A study by the same group found that climate change made last year’s heatwave in Siberia and the Australia bushfires in 2019-20 more likely, and that the recent heatwave in North America would have been almost impossible without climate change.

Hannah Cloke, professor of hydrology at Reading University, said the study, in which she was not involved, showed the importance of preparing communities for more such events in future.

“It is crucial to highlight how climate change makes floods and other impacts more likely, but it is important that we do not use climate change as an excuse for inaction,” she said.

“Individuals, local authorities and governments still have the power to make specific, local changes that can save lives and protect property from the worst impacts of floods.

“Blaming others far away, or long ago, for these problems just shirks responsibility.

“We must tackle climate change, or these problems will only get worse in the future. We have to do more to adapt ourselves to deal with the natural hazards that we face now, whether they are made worse by climate change or not.”

The Times