El Niño back before Christmas? The possibility that this climatic phenomenon, known to have a global impact on temperatures, will make an appearance in 2023 is increasingly evoked even in the highest meteorological spheres.
Such a phenomenon is characterized by an increase in water surface temperatures in the eastern equatorial Pacific of at least 0.5°C.
This return of El Niño is considered almost certain for climatologists from the German Institute in Potsdam, while their American counterparts estimated on Wednesday, April 12, that an El Niño episode had a 62% probability of occurring at the end of the summer.
As for the World Meteorological Organization, it is more cautious and puts forward a probability of only 55% of the occurrence of this phenomenon before the end of the year.
An average El Niño every four years
But it's not just about a classic El Niño. Several forecasting models suggest a "Super El Niño" for this year, analysts at the Australian Bureau of Meteorology say.
Water surface temperatures in the El Niño birth zone would then rise by more than 2°C, says The Guardian. "There have only been three episodes of 'Super El Niño' in the last forty years – in 1982-1983, 1997-1998 and 2015-2016," says Jérôme Vialard, an oceanography specialist and research director at the Institut de recherche pour le développement.
The consequences can be terrible. During the last episode, between 2015 and 2016, American scientists had observed a multiplication of epidemics around the world, including dengue and cholera.
El Niño occurs on average every three to four years. The last one was in 2018-2019, suggesting that his return this year would not be a statistical aberration.
These phenomena arise from "the accumulation of warm water in the equatorial Pacific, which will lead to an increase in surface temperatures in a large part of the Pacific Ocean," explains Grégory Beaugrand, research director at the Laboratory of Oceanology and Geosciences. "It is such a powerful phenomenon that it has an influence on the climate all over the globe," adds Jérôme Vialard.
The Pacific Ocean can, in fact, "be seen as a kind of planetary air conditioner", explains this specialist. When it's warmer, the thermometer freaks out everywhere. This is not illogical since "the Pacific Ocean covers a large part of the southern hemisphere, and a rise in temperatures naturally raises the global average," says Grégory Beaugrand.
Rising temperatures and extreme weather events
But El Niño is only one side of the climate coin playing out in the Pacific Ocean. The other is La Niña, which is the exact opposite, since it is an episode of cooling waters in the Pacific Ocean.
In fact, "when water temperatures are 0.5 °C below average [in the East South Pacific] it is estimated that we enter a La Niña episode, if the temperature exceeds the average by more than 0.5 °C, it becomes an El Niño, and between the two it is a neutral phase", summarizes Grégory Beaugrand.
The Australian Bureau of Meteorology has just indicated, on April 11, the end of a very long episode La Niña. These phenomena extend, on average over periods of one to two years, "while this time, it lasted three years, which is almost unprecedented," says Jérôme Vialard.
The world is thus emerging from a long three-year hiatus during which global temperatures were dragged down by La Niña. Hence a certain fear of seeing El Niño arrive, since La Niña has not prevented humanity from experiencing episodes of record heat, as during the summer of 2022 in France.
But it's not just about rising temperatures. El Niño is associated with a series of extreme weather events. The first to feel the effects will probably be the inhabitants of South America, towards the end of the year. It is from this geographical area that the name of this phenomenon comes: it was Peruvian fishermen who, in the seventeenth century, noticing that the sea warmed regularly towards the end of the year celebrations, began to call it "El Niño", in reference to the baby Jesus.
In South America, "the consequences are particularly strong, with very heavy rains, risks of landslides, and a drop in the productivity of the ocean," says Jérôme Vialard. In 1972-1973, an El Niño episode led to the virtual disappearance of the entire anchovy fishing industry in Peru, which was essential to the country.
In Australia, El Niño increases the risk of "drought, which aggravates that of fires," recalls the Guardian. Drought is also the usual companion of El Niño in Africa, which dangerously reduces agricultural yields and increases the likelihood of famines, says the Food and Agriculture Organization of the United Nations (FAO).
"Spring barrier of predictability"
A "Super El Niño" would cause "even more brutal changes in global temperatures," notes Grégory Beaugrand. Increases that "persist even after the end of a 'Super El Niño' for reasons that are still difficult to understand," continues this expert.
"The impacts are not only stronger, they can also be different," adds Jérôme Vialard. Thus, torrential rainfall episodes in California seem to be a "specialty" of Super El Niño episodes.
But "we must remain very cautious about the possibility of a 'Super El Niño' because it is a very difficult phenomenon to anticipate at this stage," says Grégory Beaugrand.
Spring is not the ideal time to assess the risk of a return of El Niño before the end of the year, say experts interviewed by France 24. "We are talking about a spring barrier of predictability. At this time, there are unpredictable atmospheric phenomena, such as westerly gales, which can have an impact on the probability of an El Niño episode," adds Jérôme Vialard.
For him, it would be better to wait until late spring and early summer to get a better idea of what is likely to happen or not from October.
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