Researchers from the World Weather Attribution initiative warn: Due to climate change, extreme weather events such as the storm “Boris” will occur twice as often in the future as they have done so far.
Never has a summer been warmer than in 2024, wrote the EU climate change service Copernicus at the beginning of September. A few days later, it was all over: the storm “Boris” caused torrential rain. It poured for several days.
It was the heaviest rainfall ever recorded in Central Europe. Shortly afterwards, flooding occurred in Poland, the Czech Republic, Austria and Romania. It caused great devastation. At least 24 people died and thousands had to leave their homes.
Analysis of the Attribution researchers: Climate change is to blame
For ten years, the World Weather Attribution (WWA) has been analyzing the influence of climate change on extreme weather events such as storms, extreme rainfall, heat waves and droughts. In a recent study, 24 WWA scientists from seven European countries and the USA examined the storm “Boris”.
The result of their study: Man-made climate change, which has already warmed the earth by 1.3 degrees Celsius since the pre-industrial era, doubles the likelihood of such extreme weather events and causes rainfall to increase by seven percent.
The research group stresses that the increase in precipitation is estimated very cautiously, so it could also be higher. “Boris” could therefore not remain a “once-in-a-century event” that only occurs every 100 to 300 years. Polish climatologist Bogdan H. Chojnicki, a member of the WWA research group, says:
The floods of 1997 and 2002 in Central Europe were described as once-in-a-century events, but two decades later, global warming has increased from 0.5 to 1.3 degrees Celsius, and they have occurred again. Europe is warming even faster than the rest of the world.
Cause investigation: How did this heavy rain come about?
In the exceptionally warm summer of 2024, the Mediterranean was warmer than ever and evaporated heavily. The air over the sea was also particularly warm and absorbed more moisture than usual.
The warm, moist air masses from southern Europe then met cold polar air moving over the Alps. This contrast between cold and exceptionally warm, moist air – a so-called Vb low – led to the storm that brought the extreme rainfall over a huge region.
Without protective measures, things would have been worse
Although such extreme rainfall has never been seen before, the death toll is lower than in previous extreme weather events. It is currently estimated that 24 people have died. In contrast, in 2002, when Germany, Austria, the Czech Republic, Romania, Slovakia and Hungary were affected by flooding, 232 people lost their lives. In 2021, the total number of deaths in Western Europe was more than 200.
Fewer fatalities than before – WWA scientists see this as a success of the extensive investments in forecasts and early warning systems in recent decades. Emergency management systems across Europe have been expanded. This meant that heavy rain could be predicted several days in advance. The population was warned, reservoirs were emptied preventively and flood protection walls were built.
But every fatality is one too many, say the research group. The extent of the floods has overwhelmed many – the damage is so immense that the European Union is providing ten billion euros for emergency repairs. The researchers warn of the escalating costs of climate change.
Change development plans to save lives
Maja Vahlberg, member of the research group and technical advisor to the Red Cross and Red Crescent Climate Centre, says: “These floods show how costly climate change is becoming. Even after days of preparation, the floods devastated cities, destroyed thousands of homes and led to the European Union pledging ten billion euros in aid. Countries must prepare for unprecedented floods and integrate climate change into land use planning.”
The conclusion of the WWA research group: In order to save lives in the future, development in flood-prone areas must be reduced, large-scale floodplains must be created and additional warning systems must be set up.
Even more frequent Extreme events expected
The research group notes that if the earth warms by two degrees above pre-industrial levels, which is expected for the 2050s, such extreme weather events will become even more frequent and intense.
The World Weather Attribution Group expects that at least another five percent more rain will fall and that extreme rainfall will become fifty percent more frequent than it is today – again, this is a conservative estimate.
Limiting climate change
There is no doubt: Man-made climate change will lead to heavier rainfall in many regions of the world. The WWA scientists involved in the study urgently appeal for climate change to be limited.
Joyce Kimutai of Imperial College London stresses: “Unless oil, gas and coal are replaced by renewable energy, storms like ‘Boris’ will trigger even heavier rainfall and lead to floods that destroy the economy.”
Friederike Otto, a climate scientist at Imperial College London, criticises politicians across Europe for backtracking on their climate pledges: “Climate change is an existential threat, especially for the poorer parts of society, and all Europeans need to know that tackling climate change will make their lives so much better – phasing out fossil fuels will create jobs, reduce energy bills, make cities healthier places to live and reduce the risk of deadly floods.”