2023-07-21 01:43:40
CARLOS FRESNEDA
Correspondent
London
Updated Friday, July 21, 2023 – 01:43
Climate change, El Niño, dry soils, alterations in atmospheric circulation in Europe and an increase in sea temperatures, the main causes of heat waves
A man drinks and pours water on himself in Beirut.Hassan AmmarAP
Heat waves are (and will be) increasingly frequent, long and intense. And virtually all experts agree that the main cause is climate change, combined with warming caused by the natural El Niño event in the Pacific, and exacerbated by the changes in atmospheric circulation in Europeparched soils and rising sea temperatures.
“What is happening can be explained in two words: climate change,” says Isabel Moreno, a meteorologist for the RTVE program Aquí la Tierra. “Heat waves are surely the weather phenomenon most easily attributed to climate change. You couldn’t understand so often and so many temperature records every summer if that factor wasn’t behind it.”
Three successive waves of heat (June 23, July 10 and July 17) have hit Spain and the southern Mediterranean since the start of summer. And that without forgetting the episode of extreme heat that caused Crdoba to reach 38.8 degrees at the end of April, until hundred times more likely due to the effect of climate changesegn un informe del World Weather Attribution (WWA).
“Behind extreme heat there may always be an element of natural climate variability,” warns German climatologist Friederike Otto, co-founder of WWA. “But the longer, more intense and more frequent heat waves that we are seeing in Europe are mainly caused by climate change. induced by human activity“.
From the observatory at the Grantham Institute for Climate Change in London, Otto no longer considers it necessary to wait for a new attribution study on this summer’s heat waves to take action: “The role of climate change in what is happening is already sufficiently proven.”
“We are trying unprecedented heat for humans“adds Otto. “And as long as we continue to burn fossil fuels, temperatures are going to continue to rise. But we are not facing the collapse of the climate, we are still in time to act and reach the goal of zero emissions.”
“The possibility of sequential and longer heat waves like the one we are seeing is increasing,” says Clement Albergel, climate applications scientist at the European Space Agency (ESA). “The link to human-induced climate change is very clear. Although this year there are an element that is adding fuel to the fire: the El Niño weather pattern that is taking shape in the tropical Pacific”.
The impacts of El Nio reach the entire planet. The year 2016, the hottest ever recorded, it was precisely the penultimate one in which the natural warming effect of the Eastern Pacific was experienced. “Every time El Nio occurs, global temperatures rise,” warns Albergel. “2023 may ultimately be the hottest year on record.”
A person rides a bicycle past a fountain in Rome. MASSIMO PERCOSSIEFE
June 2023 already was, and on July 3 the record for the hottest day in recent history was broken (17.18 degrees). Successive heat waves have caused temperatures above 44 degrees in Spain and around 47 degrees in Italy (the European maximum continues to be in Sicily with 48.8 degrees in 2021). In Greece, temperatures above 43 degrees forced the temporary closure of the Acropolis and caused a chain of forest fires.
The dangers to health still persist, and the meteorologist Isabel Moreno emphasizes the difference in criteria between Health and AEMET in the face of heat waves, defined as “an episode of at least three consecutive daysin which at least 10% of the stations register maximums between the 5% of the highest temperatures of their series between 1970-2000″.
The last two heat waves experienced this summer have had their origin “by the rise of a mass of very warm, dry and stable air originating in North Africa”, according to the AEMET, which also warns how “this type of gusts of extreme heat which has become more frequent in recent decades as the jet stream that dominates the Western Hemisphere has become unstable.”
The increase in the frequency of heat waves in Europe may in fact be related to the fluctuations in the jet stream (jet stream) that flies over the Eurasian region, according to the results of a study sponsored by the Potsdam Institute for Climate Impact and published in Nature.
From statistical data of the last 42 years, it has been verified that heat waves on the European continent increased three to four times faster than than in the rest of the northern mid-latitudes, such as the United States or Canada. Researchers have verified how the “double jet states” -when the current divides into two branches- last longer and cause the upward trend of heat waves in 30% of the continent.
Another factor that comes together this year is the a prolonged sequel, which may be feeding back the situation. Moist soils serve to absorb extreme heat, but when they dry, evapotranspiration decreases: less water evaporates from plants or directly from the soil, and that energy goes on to heat the air.
The slowdown in the ocean circulation and the increase in sea temperatures may also be contributing to the situation. The British Met warned at the beginning of the summer that temperatures in the eastern North Atlantic between April and May were the highest recorded in those months in a series beginning in 1850with temperatures up to four or five degrees above average (the first heat wave in June reached the United Kingdom, which has, however, been “protected” from the last two by the “double jet”).
The phenomenon of heat islands has also worsened this summer, with lows of 25 degrees at night in some of our cities. The lack of vegetation, pollution, the layer of asphalt, glazed surfaces, human crowds or refrigeration systems are some of the factors that contribute to temperatures in the city being higher (one to three degrees) than in rural areas. They know it well in Phoenix, the Arizona city that this summer has broken its own record with 19 consecutive days above 43 degrees.
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