Wednesday, August 4

The magnitude of the floods in Germany shocks scientists


Climate scientists are impressed by the intensity and magnitude of this week’s floods in Germany. They did not expect so many records to be broken in such a vast area and so soon.

Deadly heat waves like Canada’s are the new climate reality in more and more parts of the planet

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Following the deadly heat wave two weeks ago in the United States and Canada, where temperatures exceeded 49.6 ° C, flooding in central Europe has contributed to fears that man-made disturbances are worsening weather episodes. extreme more than anticipated.

The rainfall record was broken over a large area of ​​the Rhine basin on Wednesday and the consequences were devastating. Tens of people have died, tens of thousands of homes have been flooded, and the power supply has been interrupted.

In parts of the states of Rhineland-Palatinate and North Rhine-Westphalia the deluge was 148 liters per square meter in 48 hours, in an area of ​​Germany that usually receives around 80 liters of rain per square meter throughout the month of July.

The city of Hagen declared a state of emergency after the river Volme overflowed and its waters rose to levels that have only been reached four times in the last hundred years. The most striking record was that of the Cologne-Stammheim train station, the water level reached a height of 154 millimeters in 24 hours, destroying the previous maximum of 95 millimeters for the city’s daily rainfall.

“It is totally atypical”

Climate scientists have long predicted increases in floods, heat waves, droughts, storms and other extreme events due to human emissions of greenhouse gases, but the latest peaks reached exceed many expectations.

“I am amazed at how much the previous record has been broken,” says Dieter Gerten, Professor of Climatology and Hydrology of Global Change at the Potsdam Institute for Climate Impact Research. “It seems that we are not only above normal, but we have also worsened in fields that we did not expect, such as spatial extent and speed.”

Gerten, who grew up in a town in the affected area, remembers the area flooded from time to time, but like this week. Previous summer downpours have been just as intense but affected a smaller area, and past winter storms did not lift rivers to such dangerous levels. “This week’s episode is totally atypical for the region; it has lasted a long time and has affected a wide area.”

“The extremes that would have been news before are not now”

Scientists will need more time to assess how much human emissions have made this storm more likely, but the record downpour is in tune with general global trends.

“With climate change we expect all hydrometeorological extremes to be more extreme. What has been seen in Germany largely agrees with this trend,” says Carlo Buontempo, director of the Copernicus Climate Change Service at the European Center for Medium Weather Prediction. Term.

The seven warmest years on record have occurred since 2014, largely due to global warming from engine fumes, forest burning and other human activities. Computer models predict this will lead to more extreme weather, meaning more records will be broken, in more places, and with increasing frequency.

In recent weeks, North America has been the center of attention. Two weeks ago, Canada beat its daily heat record by a difference of more than 5 ° C, in addition to several local highs in Oregon and Washington. According to scientists, reaching these extreme points at those latitudes would have been virtually impossible without human-caused warming. Last weekend, the thermometer at the Death Valley control station in California read 54.4 ° C, which could reliably become the highest temperature on Earth.

Daniel Swain, a climate scientist at the University of California, Los Angeles, says so many records are being broken in America this summer that they are no longer in the news. “The extremes that would have made the news a couple of years ago are not now, because they seem small compared to the staggering increases of a few weeks ago.”

The same is happening in other countries, he says, with less media attention. “The United States is often in the spotlight, but we have also seen episodes of extraordinary heat in northern Europe and Siberia. It is not a localized phenomenon, it is part of a coherent global pattern.”

Lapland and parts of Siberia have also been hit by record heat in June. In recent weeks, unusually high temperatures have been endured in cities in India, Pakistan and Libya. The suburbs of Tokyo have been flooded with the heaviest rains since the measurements began, and in London all the rain that usually falls in July fell in a single day. Events that previously occurred every 100 years are becoming commonplace. Abnormal weather is becoming more and more normal.

Some experts fear that these recent shocks mean that the climate system has already crossed a dangerous threshold. Instead of a gradual increase in temperatures with a constant increase in extreme events, they are analyzing the possibility of an increasingly less linear, more irregular trend, caused by the effects of droughts or thaw in the Arctic Ocean. This theory is controversial, but recent events have fueled debate about this possibility and the reliability of models that are based on past observations.

“We need to better model non-linear events,” says Gerten. “In recent years, scientists have been surprised by some events that have been more intense and frequent than expected.”

Translated by Francisco de Zárate.



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