Droughts in Africa, floods in South America, record temperatures everywhere: for several years, the name El Nino has been popping up repeatedly in weather reports. The World Meteorological Organization (WMO) assured Tuesday June 2 that there was an 80% chance of an El Nino episode returning between June and August this year, increasing the risk of extreme weather events.
The World Meteorological Organization is now able to anticipate an El Nino episode up to six months in advance. This is possible thanks to the Jason program satellites which measure the height and temperature of the oceans in real time, and a network of meteorological buoys deployed in the Pacific. It is on this basis that the alert was issued.
What exactly is El Nino?
It all starts in the Pacific. Normally, tropical winds called trade winds blow from east to west and push warm surface waters towards Indonesia and Australia. On the Peruvian side, cold, nutrient-rich waters rise from the depths to the great benefit of the region’s fishermen.
But in certain years, these trade winds weaken. The warm waters, deprived of their “pusher”, overflow towards the East and abnormally warm the surface of the equatorial Pacific, near the South American coasts. This is the effect of El Nino, a thermal anomaly of around 4 to 6°C above average, explains Météo France. A phenomenon that is enough to disrupt the entire atmospheric mechanics of the planet.
The name comes from Peruvian fishermen who, in the 19th century, named this warm current “El Nino”, literally “the child” in reference to the Child Jesus, because its effects were felt around Christmas.
What are the consequences for the planet?
On the one hand, El Nino will accentuate droughts in certain regions. Australia, Indonesia, the Sahel, South Africa, part of Southeast Asia and northern South America are seeing their rains become scarce, their harvests collapse and their food security weaken. During the 2015-2016 episode, at least 3.5 million people were in need of humanitarian assistance, according to the World Food Organization (FAO). During the 2023-2024 episode, the drop in precipitation in Panama affected the level of the canal, disrupting global maritime trade, recalls the WMO.
On the other hand, certain regions find themselves drowned in rain. The equatorial Pacific, the southern United States and the Horn of Africa are receiving much higher than normal precipitation, with their share of flooding and landslides. In 1997-1998, more than 250 cm of rain fell in six months in Ecuador and northern Peru. The fish, particularly Peruvian anchovies, then fled the warmed waters, plunging the fishermen into crisis.
Does El Nino come back more often?
This is the question that worries scientists. El Nino is a very ancient natural phenomenon. The fossil corals of Papua New Guinea have borne traces of this for 130,000 years. Episodes affected pre-Columbian civilizations in Peru 4,000 years ago. Its natural rhythm has been known for a long time: it returns every two to seven years, for periods of nine to eighteen months.
To date, there is no scientific consensus on an increase in the frequency or intensity of El Nino episodes due to global warming. But there are interactions: climate change is already warming the oceans, and this warmer base amplifies its effects.
Each episode is superimposed on an already warmer planet. “El Nino adds to climate change and can lead to temperatures higher than average by around 0.1 to 0.2°C, which will create extreme events,” specifies Robert Vautard, co-president of the IPCC, on TF1.
Are France and Europe concerned?
France and Europe are not directly concerned, but they are not completely spared. El Nino acts on Europe through what climatologists call “tele correlations”, very long-distance atmospheric interactions.
In practice, El Nino years tend to produce wetter autumns and colder, drier winters from January to March in Northern Europe. In the Mediterranean basin, there was a slight increase in autumn precipitation, of around 10%, the year preceding the phenomenon, according to data compiled by climatological research.
