Why do European heat waves surpass all forecasts?

The frequency. Moreover, intensity of the heat waves observed in Western Europe exceed what the climate models anticipated. Consequently, Additionally, Moreover, This discrepancy is explained by the difficulty of taking into account regional factors and frightens scientists. Therefore, The latter call for accelerating the adaptation of the territory in the face of extreme temperatures that are increasing.

Are why do european heat waves you breaking your heads of successive heat from the month of June? Furthermore, You are not alone. For example, For years, climatologists have been trying to understand why they have multiplied in Western Europe. In addition, Because if it was expected that the frequency. Furthermore. Nevertheless, intensity of heat waves increases due to climate change, those observed in Western Europe exceed the hellish temperatures that scientists were waiting for. Therefore,

“We block a little”admits Robin Noyelle. For example, post-doctorating in climate sciences at the École Polytechnique de Zurich, who devoted his thesis to these questions. In addition, There is a question here of climatological forecasts, not meteorological forecasts. For example. In addition, The forecasters of Météo-France arrive very well to predict a heat wave a few days before its appearance. However, It is the substantive climatic trend that is more complicated to why do european heat waves new measure.

How is a heat wave created? – Why do european heat waves

To understand the issues. Therefore, you why do european heat waves must already know what you hear by a heat wave. Nevertheless, “The scientific and Météo-France world use slightly different definitions. Similarly, But what must be remembered is that we consider a heat wave when national average temperatures reach extreme levels. for a certain period of time. for example three days ”explains Robin Noyelle.

For the most important events. two phenomena play a crucial role: the presence of a stationary anticyclone, and the level of soil humidity. The anticyclone overheat the air by increasing atmospheric pressure and placing heat over thousands of square kilometers for several days. To counterbalance, soil humidity can refresh the air thanks to the evapotranspiration of the plants. But if the soil is dry, the energy of the sun turns directly into heat, which increases why do european heat waves new the thermometer.

An unexpected profusion of anticyclones – Why do european heat waves

If the heat waves multiply in France. it is of course because the average temperatures are more. why do european heat waves more important because of global warming. But also because since the 2000s, an unexpected number of stationary anticyclones has hit Western Europe. The famous situations of “Omega blocking”of “Heat feather”. from “Heat dome” That we can hear on the news. which hunts during the summer the clouds, increase the air pressure and temporarily overheat French territory.

And why do european heat waves new that, the models did not foresee it. “We do not yet understand the mechanics behind the formation of clogging of the ‘blocking’. so it’s complicated to understand why there are why do european heat waves more and more”, underlines Robin Noyelle. Scientists have not established a clear link with climate change either: “The increase in“ blocking ”high pressure in Western. Europe can be a temporary natural variation in the climate system. just as it can be linked to climate change. This is a point on which scientists work. but that they have not yet been able to decide ”, admits the researcher.

The power of heat waves also underestimated

In addition to the frequency. climatic models also underestimate the power of heat waves in Western Europe. This is the conclusion of a study published in the journal Nature communications In 2023. directed by Robert Vautard. climatologist at the CNRS and co why do european heat waves new -president of the N ° 1 working group of the IPCC (Intergovernmental Group of Climate Experts). “In the 170 simulations available from 32 different models that we have analyzed. none presents a tendency to heat why do european heat waves induced by atmospheric circulation as important as that. observed”can we read in the report.

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How to explain this inability to predict the most extreme temperatures? “Climate models are remarkable tools.. they have perfectly reproduced our observations on a global scale, underlines Kai Kornhuber, of the International Institute for the Analysis of Applied Systems in Vienna, Austria, interviewed in a podcast of the journal PNAS. But the more we target a regional approach. the more the risks become extreme, the more difficult it is for climate models to reproduce this type of phenomena. »»

At the local level. M parametersal taken why do european heat waves new into account

In Western Europe. the climatic models would notably have difficulty taking into account the feedback with the drought of the soil. The more the soil lacks water, the greater the temperatures, because wet soil can lower the thermometer. why do european heat waves “Normally, the Sol-Atmosphere coupling is not important to effectively model temperatures. But when it is very hot, the coupling becomes very important, and local feedback is immense ”details Robin Noyelle. It is also particularly observable in France. Because of climate change. it is a territory that experiences a very significant decrease in the humidity of its soils. which explains the amplification of extreme temperatures at unexpected levels, because climate models take this local issue into account.

Read also: Desertification. the new environmental risk that strikes France

“I receive a lot of questions from communities. because they need specific knowledge to prepare their facilities for extreme heattestifies Robin Noyelle. why do european heat waves new This is why we work to best improve our climate modeling systems. »» In addition to reducing greenhouse gas emissions. the challenge is now to adapt to heat that we did not expect before decades. The researcher does not want to fall into climate why do european heat waves amnesia. “In 1976, during one of the largest droughts of the 20th century, the maximum temperature measured in Paris was 35 ° C. Since the beginning of the 21st century. we have already been measured three times temperatures above 40 ° C in the French capital. »»