Climate change makes the weather in humid areas not only more humid, but above all more extreme. Researchers expect more heavy rain.
Berlin – An international team of researchers warns of an increasing number of extreme weather events worldwide as a result of climate change.
About two thirds of the mainland are facing a wetter and at the same time more fluctuating climate. The difference between extremely dry and extremely wet weather will therefore be greater there.
In contrast, a third of the land area is becoming drier, according to the study, which was published in the journal “Science Advances”. The increase in extreme precipitation events poses an additional threat to infrastructure and to society in general.
Global warming makes the climate more unbalanced – “more extreme in both wet and dry conditions,” write the authors around Wenxia Zhang from the Chinese Academy of Sciences in Beijing.
Precipitation increases on a global average
“The water cycle intensifies with global warming, with the global mean precipitation increasing by 1 to 3 percent per degree of temperature increase,” the authors write, referring to earlier studies. But this does not happen evenly. Extreme precipitation could increase even more if there is enough water in the atmosphere in the regions. According to a long-known equation, the possible water content in the atmosphere could increase by 6 to 7 percent per degree, which is why more rain is then possible.
According to the authors, humid regions are becoming more variable, i.e. there is more heavy rainfall, among other things. This applies, for example, to the Indian monsoon region.
Around a third of the land area is becoming drier, but not all regions in the same way. The authors include south-western Europe and southern Africa among the regions that are becoming drier and at the same time more fluctuating in the weather. The risk of droughts and scarce water resources is increasing there. In the Mediterranean region, which is also becoming drier, and the Amazon region, the water cycle is becoming weaker and weaker with ever lower and less variable rainfall. These assessments are important so that agriculture and water management can adapt to them.
Jetstream is changing
Changes in the so-called jet stream played a role in the weather extremes, said hydrologist Fred Hattermann from the Potsdam Institute for Climate Impact Research (PIK) of the German Press Agency. This works like a motor that moves the high and low pressure areas across Europe in the upper atmosphere. It is driven by the temperature difference between the equator and the Arctic.
“But the engine is getting weaker because the Arctic is warming up more than the equator due to climate change,” says Hattermann. This could lead to longer-lasting weather conditions in an area. “Persistent weather with a lot of precipitation then leads to floods, while persistent weather without rain leads to drought and drought.” The danger was recently made clear by the flood disaster in Rhineland-Palatinate and North Rhine-Westphalia.
The study shows that one cannot concentrate solely on mean values when considering, said Hattermann’s PIK colleague, the meteorologist Peter Hoffmann. It is therefore important to see how values are composed. “That makes the choice of the right protective measures so complicated, because you can expect the average course less often, but rather the extremes.” Dpa
