It is not over yet, but summer 2022 will certainly stay stuck in the memories of a lot of people. Countless heatwaves, very strong drought, fires… Since June, one’s body has been put through the mill with heat peaks very difficult to handle, a rain that does not fall. But then, how to explain these many heatwaves, more frequent than over the past summers?
In a study released this July 4 in the prestigious Nature magazine, a team of five scientists points out “double jet-stream”. They say the phenomenon has originated most heatwaves hitting Western Europe and France this summer.
“Here we identify Europe as a heatwave hotspot, exhibiting upward trends that are three-to-four times faster compared to the rest of the northern midlatitudes over the past 42 years”, they explain in their study. But then, how to explain these growing trends? The team of scientists also blames the “atmospheric dynamical changes via an increase in the frequency and persistence of double jet stream states over Eurasia”.
New study out of France says that the creation of a "double jet stream" due to global warming and the loss of jet stream stability is a major factor behind the heatwaves this year. The authors say Europe, in particular the UK and France, is over-exposed to this phenomenon. pic.twitter.com/sFGyl2ylYl
— XR Cambridge (@xr_cambridge) August 8, 2022
To understand what “double jet-stream” is, let us first focus on the standard jet-stream. It usually characterizes in a corridor of strong winds allowing to regulate – on the Old Continent – the cold air streams from Greenland and the warm air stream from Sahara – among others. But global warming considerably changes the game. as Greenland is warming quicker than other places in the world, cold air from this country is less strong as before, and now not enough to face the warm streams from Sahara. Jet-stream not only decreased, but also moved north.
Furthermore, this decrease creates a division of jet stream, leading to the famous “double jet-stream”. As a consequence? Western Europe and France are stuck between these two streams, and hot stream stay put over these regions.
“We find that double jet occurrences are particularly important for western European heatwaves, explaining up to 35% of temperature variability. The upward trend in the persistence of double jet events explains almost all of the accelerated heatwave trend in western Europe, and about 30% of it over the extended European region”, searchers say.
Because of climate change, this phenomenon is unfortunately likely to increase. Still according to scientists, France and the south of the United Kingdom are likely to be the places the most exposed to “double jet-stream” in the coming years.
