2023-05-05 19:00:31
El Niño regularly brings flooding to the usually dry Peruvian coast. JULIO REANO / AFP
FOCUS – The United Nations has issued an alert on the consequences of floods and drought implied by this natural anomaly. A heat record could be reached in the year.
«The Terrible Child of the Pacificis making a comeback this year. A new El Niño episode will begin in the second half of 2023 and will continue until 2024, the World Meteorological Organization (WMO), the UN’s specialized agency, announced on May 3. This natural phenomenon is characterized by a rise in the temperature of the eastern Pacific Ocean, off the coast of Peru, and results in a rise in the global temperature of the planet.
In the latest WMO bulletin, scientists estimate between 70 and 80% the probability that an El Niño episode will begin between July and October 2023. This natural anomaly occurs every three to seven years for an average duration of nine to twelve months. The beginning of the episode is generally in the spring then intensifies between October and December, to disappear during the winter.
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This phenomenon is the consequence of a disturbance in the general atmospheric circulation between the poles and the equator. Its appearance causes a displacement of the precipitation zones towards the east of the Pacific Ocean and prevents the upwelling of cold water along the coast of South America. Under the effect of a Niño, the temperature of the Pacific Oceanincreases by 0.5 to 4°C compared to normalsays Fabio d’Andrea, CNRS researcher at the Dynamic Meteorology Laboratory.
El Niño – the child in English – was named by Peruvian fishermen hundreds of years ago. In question, the disappearance of fish that migrated to cold waters because of an underwater heat wave at Christmas time. A poisoned gift attributed to the child Jesus.
Drought, floods, cyclones…
«The world must prepare for the development of El Niño“Warned WMO chief Petteri Taalas in a statement. The movement of precipitation towards South America could thus lead to severe droughts in Australia and Indonesia. On the contrary, rains could be increased in the northwestern United States, southern South America and the Horn of Africa. This rainfall may be good news for this African region hard hit by drought, due to global warming.
But will El Niño increase the risk of extreme weather events? “Not necessarily, they will just be distributed to another place“, answers Christophe Cassou, CNRS research director at CERFACS in Toulouse. “The usually dry Peruvian coast could experience flooding“, he gives as an example. “The number of cyclones in the Caribbean will also decrease to rage in the central Pacific, towards Polynesia”continues the researcher.
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However, the impacts of Niño will be little felt in Europe because “it mainly affects the Pacific tropics and the American continent“, he reassures. In view of the previoussuper child» over the periods of 1982-1983, 1997-1998 and 2015-2016, the consequences on our continent were «limited“. Christophe Cassou evokes “heavier precipitation», in particular around the Mediterranean at the beginning of autumn.
Beat the 2016 heat record
Niño’s last event of the 2015-2016 period had been particularly powerful. The year 2016 has since been considered as “the warmest year on record due to the “double effect” of the El Niño and the warming caused by greenhouse gases“, underlines the WMO in its report. Compared to the period from 1901 to 2000, “the year 2016 experienced a temperature anomaly of +1°C“says Christophe Cassou.
If for the moment it is too early to predict the intensity or the duration of El Niño to come, “its impact on the atmosphere will certainly be stronger than in 2016“Warns Christophe Cassou. Over the past ten years, the global temperature of the Earth has increased by 0.3°C. As a result, “if this year’s Niño is virulent, it is almost certain that we will break the heat record of 2016“, he explains.
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El Niño is to be differentiated from La Niña, the opposite phenomenon which occurs alternately and at the same frequency. It causes a cooling of the waters of the Eastern Pacific. For three years, the Earth had been under the influence of this phenomenon. For Christophe Cassou, it is also one of the factors that explains “why the global temperature record has not yet been broken».
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