‘Nowhere is safe’ – lethal floods in Europe were at least 20pc more likely to happen due to global climate change, say scientists
Destroyed houses are seen close to the Ahr river in Schuld, Germany last month
Isla Binnie
Isla Binnie
August 25 2021
Climate change has made extreme rainfall events of the kind that sent lethal torrents of water hurtling through parts of Germany and Belgium last month at least 20pc more likely to happen in the region, scientists have said.
The downpour was likely made heavier by climate change as well.
A day of rainfall can now be up to 19pc more intense in the region than it would have been had global atmospheric temperatures not risen by 1.2C above pre-industrial temperatures, according to research by the World Weather Attribution (WWA) scientific consortium.
“We will definitely get more of this in a warming climate,” said the group’s co-leader Friederike Otto, a climate scientist at the University of Oxford.
Recalling that she urgently contacted relatives living in the affected areas to make sure they were safe when the floods hit, Dr Otto added: “Extreme weather is deadly. For me it was very close to home.”
With extreme weather events dominating headlines in recent years, scientists have been under pressure to determine how much climate change is to blame.
In the past year alone, scientists found that US drought, a deadly Canadian heatwave and wildfires across the Siberian Arctic have been worsened by a warming atmosphere.
The July 12 to 15 rainfall over Europe triggered flooding that swept away houses and left more than 200 people dead in Germany and Belgium.
Thousands were forced to flee their homes in the Netherlands.
o“The fact that people are losing their lives in one of the richest countries in the world – that is truly shocking,” said climate scientist Ralf Toumi at the Grantham Institute, Imperial College London, who was not involved in the study. “Nowhere is safe.”
Although the deluge was unprecedented, the 39 WWA scientists found local rainfall patterns are highly variable.
They conducted their analysis over a wider area spanning parts of France, Germany, Belgium, the Netherlands, Luxembourg and Switzerland and used local records and computer simulations to compare the July flooding event with what might have been expected in a world unaffected by climate change.
Because warmer air holds more moisture, summer downpours in this region are now 3pv to 19pc heavier than they would be without global warming, the scientists found.
The event itself was anywhere from 1.2 to 9 times – or 20pc to 800pc – more likely to have occurred.
That broad range of uncertainty was partly explained by a lack of historical records and worsened by the floods destroying equipment that monitored river conditions.
CLIMATE CHANGE MADE GERMAN EU FLOODING WORSE
Climate change has made extreme rainfall events of the kind that sent lethal torrents of water hurtling through parts of Germany and Belgium last month at least 20% more likely to happen in the region, according to an international study published Tuesday (August 24).
Germany floods were up to 9 times more likely because of climate change, study estimates
By Angela Dewan, CNN
Record rainfall that triggered deadly floods in Western Europe in July was made between 1.2 and 9 times more likely by human-caused climate change, according to a new study.
By Angela Dewan, CNN
Record rainfall that triggered deadly floods in Western Europe in July was made between 1.2 and 9 times more likely by human-caused climate change, according to a new study.
© Michael Probst/AP The Ahr River in Insul, Germany, on July 15, 2021 after heavy rainfall.
At least 220 people were killed between July 12 and 15 -- mostly in Germany, though dozens also died in Belgium -- and homes and other buildings were destroyed in flash flooding that followed heavy rainfall. Some parts of the region experienced more rain in a single day than they would typically expect in a whole month.
The study, conducted by 39 scientists and researchers with the World Weather Attribution (WWA) project, also found that the most extreme rain was a once-in-400-year event, and that climate change increased the intensity of daily extreme rainfall by 3% to 19%.
"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," Friederike Otto, the associate director of the Environmental Change Institute at the University of Oxford, said in a statement. "This is an urgent global challenge and we need to step up to it. The science is clear and has been for years.
The one-in-400-year frequency only refers to the particular region studied and does not mean it will be another 400 years until other parts of Europe, or the world, will see a similar weather event, explained Maarten van Aalst, a professor of climate and disaster resilience from the University of Twente in the Netherlands.
"In this case, [the projection for next year is] possibly worse because, year by year, if the trend so far is that the climate is increasing, the risk will continue to grow. So, if anything, we're expecting a higher chance of this happening next year than this year. But it's basically a one-over-400 chance every single year," van Aalst said at a news conference.
The scientists focused on the areas around the Ahr and Erft rivers in Germany and the Meuse in Belgium, where rainfall records were broken. But they also took into account what was happening across a larger region, including parts of France, the Netherlands, Luxembourg and Switzerland, to establish how the extreme weather event had been influenced by increasing global temperatures.
The scientists looked at weather records and used computer simulations to compare the picture today -- in a world that is 1.2 degrees Celsius warmer than it was in pre-industrial times -- to that of the late 1800s.
They warned that the warmer Earth gets, the more frequent and intense these rain events will be. Specifically, if global temperatures rose to 2 degrees above pre-industrial levels, the intensity of rain in a single day would increase by a further 0.8 to 6% and would be between 1.2 and 1.4 times more likely to happen, their models project.
River measurement stations destroyed
Van Aalst said that the findings should be a "wake-up call" for governments and local leaders to improve their preparedness for extreme weather events, including looking at how homes are constructed so that children, the elderly and people with disabilities can reach safety in events like floods or fires.
"I hope it's a wake-up call also to people that have not just been affected by this one, but also people elsewhere -- because it's been heatwaves elsewhere, where I could tell a similar story," he said. "We are just facing more extreme events of many kinds, and the only thing we can do is, on the one hand, closing the tap off the increase in greenhouse gases to avoid the risk of getting further out of hand, and on the other hand, preparing for that more extreme climate."
The scientists acknowledged their estimate -- 1.2 to 9 times more likely, due to climate change -- was a wide range, and explained that the models they used and the data available to them around such localized events prevented them from narrowing their findings down further.
They were also missing crucial data, as some measurement stations were destroyed by the floods.
The study acknowledged that a number of conditions had worsened the severity of the floods, including that the soil in the region was already saturated, and that the terrain in some locations, with narrow valleys and steep sloping mountains, led "to funnel-like effects in the event of extreme floods." Those factors were taken into account in their models.
This summer, the Northern Hemisphere has experienced wide range of extreme weather events beyond deadly flooding, including record-breaking temperatures that in some instances have triggered wildfires in the US, Canada, Siberia, Algeria and southern Europe.
On August 14, rain fell on the summit of Greenland for the first time on record, as temperatures there rose above freezing for the third time in less than a decade. The warm air fueled an extreme rain event that dumped 7 billion tons of water on the ice sheet.
The US state of Tennessee is now experiencing heavy rains and deadly floods, as the National Weather Service in Nashville reported more than 17 inches of rain in the city of McEwen, possibly setting a new state record for 24-hour rainfall. If verified, it would smash the previous state record set in September 1982 with 13.6 inches of rain the city of Milan.
At least 220 people were killed between July 12 and 15 -- mostly in Germany, though dozens also died in Belgium -- and homes and other buildings were destroyed in flash flooding that followed heavy rainfall. Some parts of the region experienced more rain in a single day than they would typically expect in a whole month.
The study, conducted by 39 scientists and researchers with the World Weather Attribution (WWA) project, also found that the most extreme rain was a once-in-400-year event, and that climate change increased the intensity of daily extreme rainfall by 3% to 19%.
"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," Friederike Otto, the associate director of the Environmental Change Institute at the University of Oxford, said in a statement. "This is an urgent global challenge and we need to step up to it. The science is clear and has been for years.
The one-in-400-year frequency only refers to the particular region studied and does not mean it will be another 400 years until other parts of Europe, or the world, will see a similar weather event, explained Maarten van Aalst, a professor of climate and disaster resilience from the University of Twente in the Netherlands.
"In this case, [the projection for next year is] possibly worse because, year by year, if the trend so far is that the climate is increasing, the risk will continue to grow. So, if anything, we're expecting a higher chance of this happening next year than this year. But it's basically a one-over-400 chance every single year," van Aalst said at a news conference.
The scientists focused on the areas around the Ahr and Erft rivers in Germany and the Meuse in Belgium, where rainfall records were broken. But they also took into account what was happening across a larger region, including parts of France, the Netherlands, Luxembourg and Switzerland, to establish how the extreme weather event had been influenced by increasing global temperatures.
The scientists looked at weather records and used computer simulations to compare the picture today -- in a world that is 1.2 degrees Celsius warmer than it was in pre-industrial times -- to that of the late 1800s.
They warned that the warmer Earth gets, the more frequent and intense these rain events will be. Specifically, if global temperatures rose to 2 degrees above pre-industrial levels, the intensity of rain in a single day would increase by a further 0.8 to 6% and would be between 1.2 and 1.4 times more likely to happen, their models project.
River measurement stations destroyed
Van Aalst said that the findings should be a "wake-up call" for governments and local leaders to improve their preparedness for extreme weather events, including looking at how homes are constructed so that children, the elderly and people with disabilities can reach safety in events like floods or fires.
"I hope it's a wake-up call also to people that have not just been affected by this one, but also people elsewhere -- because it's been heatwaves elsewhere, where I could tell a similar story," he said. "We are just facing more extreme events of many kinds, and the only thing we can do is, on the one hand, closing the tap off the increase in greenhouse gases to avoid the risk of getting further out of hand, and on the other hand, preparing for that more extreme climate."
The scientists acknowledged their estimate -- 1.2 to 9 times more likely, due to climate change -- was a wide range, and explained that the models they used and the data available to them around such localized events prevented them from narrowing their findings down further.
They were also missing crucial data, as some measurement stations were destroyed by the floods.
The study acknowledged that a number of conditions had worsened the severity of the floods, including that the soil in the region was already saturated, and that the terrain in some locations, with narrow valleys and steep sloping mountains, led "to funnel-like effects in the event of extreme floods." Those factors were taken into account in their models.
This summer, the Northern Hemisphere has experienced wide range of extreme weather events beyond deadly flooding, including record-breaking temperatures that in some instances have triggered wildfires in the US, Canada, Siberia, Algeria and southern Europe.
On August 14, rain fell on the summit of Greenland for the first time on record, as temperatures there rose above freezing for the third time in less than a decade. The warm air fueled an extreme rain event that dumped 7 billion tons of water on the ice sheet.
The US state of Tennessee is now experiencing heavy rains and deadly floods, as the National Weather Service in Nashville reported more than 17 inches of rain in the city of McEwen, possibly setting a new state record for 24-hour rainfall. If verified, it would smash the previous state record set in September 1982 with 13.6 inches of rain the city of Milan.
© Thomas Frey/picture alliance/Getty Images Flooding in July damaged the main road leading through the Ahr river valley in Germany.
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