The planet is burning, but most French people are wearing a light sweater: This is the paradox of summer in 2023. July was marked by scorching temperatures around the Mediterranean and spectacular fires in Sicily and Greece, prompting the UN to declare the start of "the era of global boiling," while at the same time, gloomy, rainy weather descended over the northern half of the country.
Unsettling? Yes, if conversations in everyday life are anything to go by. On social media, some climate change skeptics have even seized on the paradoxical weather, making jokes about what some are calling an "asymptomatic heatwave." And yet the current situation does not contradict the science and nor does it minimize the seriousness of the situation. Here's why:
Because of the jet stream. This "wind tube," as France's national weather forecaster Météo-France calls it, crosses the globe from west to east in the upper atmosphere, bringing wind and precipitation. It usually moves over Scandinavia in summer, but not this year. "It is currently located over the north of France, which explains why temperatures are cooler," explained François Gourand, forecaster at Météo-France.
As a result, the mercury plummeted during the second half of July, with France largely protected by the low-pressure veil. However, France's situation is unique: In contrast, July 2023 was the hottest month on record worldwide.
Back in June, scientists were worrying about a scorching summer, not least because of the El Niño phenomenon. This powerful high-pressure system, responsible for some of the hottest years on record, was set to add to the steady rise in summer temperatures. But the fundamental dynamics of climate, which are established over the long term, can be blurred by numerous short-term meteorological phenomena, which are linked to atmospheric air and wind flows: This is the difference between climate and weather.
The shift in the jet stream was "not really anticipated," admitted Gourand, and "it is part of the variability of weather." It is expected to move northwards across Europe from the second week of August, leading to a return to seasonal norms across France.
It's too early to say: For that, complex attribution studies would be needed, and the phenomenon would have to be repeated over several summers. That's the problem we're currently facing when it comes to studying the climate: Without the benefit of hindsight, it's difficult to tell the difference between short-term meteorological phenomena and new climatic phenomena.
In any case, the idea that the jet stream is influenced by climate disruption cannot be ruled out, since it moves according to changes in pressure and temperature contrasts. A study by the University of Pennsylvania showed in 2022 that climate disruption was causing a change in its behavior, which has accentuated its propensity to change latitude. This is what is happening this summer.
"France lies between the Mediterranean, hit by a heat dome of exceptional magnitude, and northern Europe, which is subject to low-pressure conditions," explained Gourand. "The heat has probably accentuated the contrast, which feeds the famous jet stream."
No. Firstly, because if you move away from the north of France, temperatures were (very) high in the south. In July, Météo-France reported that Corsica experienced its second longest heatwave since 1947. Furthermore, several records were set in Provence-Alpes-Côte d'Azur and Pyrénées-Occidentales, with readings of 39.2oC in Cannes on July 19, and 40.4oC in Serralongue. "The month of July is the 15th hottest since 1900 for France as a whole," pointed out climatologist Christine Berne in the French daily Libération.
June had already ranked as the second hottest month over the 1900-2023 period, according to Météo-France records. And while France is unlikely to experience a heatwave between now and August 15, temperatures are expected to rise again after that.
No, on the contrary. In all forecasting models, rain does not disappear, but falls differently, more sparsely and more intensely. "In regions like France, the total amount of precipitation will fluctuate little," confirmed CNRS researcher Julie Deshayes. "But it's the concentration of precipitation in a smaller window of time that changes: What we had over a month before, now we'll have over two days. This, too, is an indicator of climate change."
As a result, the northern half of France – for example in the Doubs – was hit by violent thunderstorms and torrential rain. "We think that as soon as there's no more heat wave, there's no global warming , but that's not how it works," said Deshayes. In reality, global warming is accompanied by more general disruption, which takes the form of extreme episodes, both in one direction (heat waves, drought) and the other (cold snaps, storms, torrential rain). In Beijing, a record amount of rain fell in three days at the end of July, leaving dozens dead and missing.
Conversely, Italy, Greece, Turkey, Tunisia and Algeria experienced extreme temperatures in the second half of July, with peaks of 48.2oC in Jerzu (Sardinia), 47.8oC in Syracuse (Sicily), 48.7oC in Algiers, 49oC in Tunis, and there were fires in Croatia, Portugal and Bulgaria.
It's true that hot summers are expected in this part of the world, and very high temperatures have already been recorded in isolated cases. "But the fact that they are occurring with increasing frequency and amplitude is characteristic of climate change," said Deshayes, who sees in them "a glimpse of the climate of the future," with increasingly intense and frequent heat waves.
The heat dome that marked the month of July around the Mediterranean took forecasters by surprise. "If we look at the heat waves in southern Europe, whose duration and intensity is shaping up to be exceptional, we're looking at an event that we would expect to happen more around 2050," climatologist Davide Faranda recently told Le Monde.
Not local weather, which is by definition changeable. Many short-term phenomena mask long-term upheavals. One indicator that seems to provide indisputable proof of global warming is ocean temperatures. This is because the oceans capture a large proportion of atmospheric heat, and unlike air, they are less changeable, less exposed to contradictory atmospheric dynamics, and retain this heat for longer. "This makes them a better indicator of global warming," said Deshayes. At the end of July, the Mediterranean Sea and the North Atlantic broke all-time records.
Translation of an original article published in French on lemonde.fr; the publisher may only be liable for the French version.