No prizes for guessing how this story ends: it’s your fault, or so the researchers want us to believe. Human-caused emissions of trace gases are supposed to have made weather systems more prone to being stationary for longer, reports Phys.org. But where’s the mechanism that points to humans, we may ask. Blocked weather itself is a long-known and well understood weather phenomenon.
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“In our study, we show that persistent weather conditions have an increasing similarity in summer over the North Atlantic, Europe and Siberia, favoring more pronounced extreme weather events. In Europe alone, about 70% of the land area is already affected by more persistent weather situations,” says Peter Hoffmann from the Potsdam-Institute for Climate Impact Research (PIK), lead author of the study published in Nature’s Scientific Reports.

“This means that people, especially in densely populated Europe, will likely experience more and also stronger and more dangerous weather events.”

Prolonged sunny or rainy conditions lead to extreme events

To prove this, the scientists analyzed the persistence of specific weather conditions. They applied established image comparison methods on atmospheric data, comparing millions of successive weather circulation patterns worldwide over the last 40 years. They especially looked at two individual extreme events, the 2010 heat wave over Russia and the extraordinary dry summer over Europe in 2018.

“We found that weather patterns in general are more persistent now than some decades ago,” says Hoffmann. “Especially in summer, heat waves often last longer now, and also rainfall events tend to linger longer and to be more intense. The longer these weather conditions last, the more intense the extremes can become, both on the warm and dry side as well as on the steady rain side.”

The rise in persistent weather conditions is to a large extent due to dynamical changes in the atmosphere as the westerly winds tend to stop pushing forward weather systems which therefore become more persistent, turning some sunny days into heatwaves of several weeks as well as intensive rainfall into floods.

Full report here.

via Tallbloke’s Talkshop

December 8, 2021 by oldbrew

Too dry, too hot, or too wet: Increasing weather persistence in European summer , say researchers