From one end of the hemisphere to the other, a heat wave that is suffocating. In Italy and Spain, tourists and locals are overwhelmed by the heat. 35°C were recorded in Berlin, and the Greek authorities were forced to close the Acropolis of Athens during the hottest hours of the day on Sunday for the third consecutive day, when temperatures can reach 41°C. In Asia, a temperature record for mid-July was crossed on Sunday in the Xinjiang region, in the west of the country with 52.2°C, according to the national meteorology. In the United States, where the weather services describe an “oppressive” heat wave in the south of the country, the heat wave alert concerned nearly 100 million people across the country on Monday morning.
A record heat wave has settled on the surface of the globe, further highlighting the consequences of human-caused global warming. Scientists assure it, with this one, heat waves are more frequent, more intense and longer. In this context, the heat waves observed on the globe are also more probable, but their concomitance does not respond to a single meteorological event. “The situations observed in China, the United States and Europe are not a priori linked to each other, but depend on local atmospheric phenomena”, explains Aglaé Jézéquel, climatologist at the Dynamic Meteorology Laboratory of the University of Paris Sciences and Letters.
Cascading records
In Europe, an important “heat dome” has settled, an anticyclonic phenomenon of high atmospheric pressure which retains a hot air whose heat intensifies still further. These blocking phenomena explain in particular the major episodes of heat waves observed during the summers of 1976 and 2003 in Europe; and heat waves with forest fires in the summer of 2010 in Russia, underlined in an article in The Conversation, Cathy Clerbaux, research director at the CNRS, and at the LATMOS laboratory of the Institut Pierre Simon Laplace (IPSL). In some regions there are now more blocking phenomena or heat domes than before, note the scientists who believe that climate change can play a role.ole in the geographical extent of these phenomena.
In some regions, such as Andalusia in southern Spain, these heat domes could cause temperatures 10 to 15°C higher than normal. France seemed to escape it for a few days, but the heat is rising from the south. While the Minister of Ecological Transition and Territorial Cohesion, Christophe Béchu, launched his national heat wave management plan on Monday July 17 in 23 French departments, Météo-France placed seven departments on heat wave orange vigilance, until at midnight Tuesday evening.
These temperatures do not surprise scientists, however. “In a changing climate, records are also meant to be broken. What makes it visible is the number of records that fall annually, which is much higher than what we knew previously”, explains Aglaé Jézéquel . These localized heat waves are therefore to be read in a global atmosphere largely warmed by greenhouse gas emissions. Last week, the World Meteorological Organization (WMO) revealed that the period from July 3 to 9 was the hottest week on record globally. Already last May, the WMO had warned that the coming years would be likely to break records. “Global temperatures are expected to reach record highs over the next five years, driven by heat-trapping greenhouse gases and a natural phenomenon, El Niño,” she wrote on May 17.
Major impacts
For the moment, it is difficult to incriminate the El Niño phenomenon as responsible for these temperatures on the European continent, its effects being rather expected next spring. “In Europe and on this date, it cannot yet be El Niño, the phenomenon is only settling in the Pacific”, deciphers Cathy Clerbaux. A study published in the journal Environmental Research Letters in 2020 pointed out that the extreme heat observed in North America, Eastern Europe, Central Asia and Northeast Asia tended to be more frequent during the summers of development of the La Niña phenomenon (observed previously) and less frequent during the development phases of El Niño. But climate change, by greatly increasing the probability of such weather events occurring, makes the occurrence of simultaneous heat waves on the globe more likely. Last year, the first half of the year also saw several overlapping heat waves in northern India, southwestern Europe and North America.
The consequences of these heat waves are cascading. “Extreme weather – an increasingly frequent event in our warming climate – has a major impact on human health, ecosystems, economies, agriculture, energy and water supplies. underscores the growing urgency to reduce greenhouse gas emissions as quickly and as deeply as possible.” in a note WMO Secretary-General, Professor Petteri Taalas. Beyond the heat that makes organisms suffer, heat waves also make the air less breathable. To the direct consequences on the health of populations, to the devastating effects of torrential rains swollen by these temperatures, are added major impacts on ecosystems, such as the weakening of CO2 absorption capacities by forests or destructive sea heat waves for many organizations.