Sea surface temperature variation in the tropical Pacific Ocean between February and May 2026. An anomalous Pacific current<\/p>\n This occasional anomalous warm ocean current in the Pacific was originally noted by 19th-century Peruvian fishermen. They called it El Ni\u00f1o \u2013 \u201cthe child\u201d in Spanish \u2013 because it often arrived around Christmas time.<\/p>\n It occurred when warm waters from the equatorial Pacific replaced the usual cold waters off the coasts of Ecuador (south of the city of Guayaquil), Peru and northern Chile. These waters are normally quite cold due to the Humboldt Current<\/a> \u2013 which flows from south to north along this sections of South America\u2019s coastline \u2013 and due to the upwelling of deep cold waters. <\/p>\n The impact of these currents is significant. Take, for instance, the Chilean city of Antofagasta on the Pacific coast, and Rio de Janeiro on the Atlantic coast. They are at almost exactly the same latitude, the Tropic of Capricorn, but their average sea temperatures are very different: around 18\u00b0C in Antofagasta and 24\u00b0C in Rio de Janeiro. <\/p>\n For Peruvian fishermen, the arrival of the warmer El Ni\u00f1o current meant the disappearance of their most abundant and prized fish, the anchoveta, which thrives in cold, plankton-rich waters.<\/p>\n Read more: An ocean and atmospheric phenomenon<\/p>\n In the 1920s, British physicist and climatologist Gilbert Walker<\/a> made a surprising discovery. While analysing vast amounts of atmospheric pressure data, he realised that when pressure increased in the South American Pacific, it decreased in northern Australia and Indonesia, and vice versa. In other words, these two regions of the planet, thousands of kilometres apart, were connected in terms of atmospheric pressure behaviour. This is what we now call a teleconnection, a long-distance meteorological link. <\/p>\n This coordinated oscillation in atmospheric pressure across the South Pacific was named the Southern Oscillation. But what does El Ni\u00f1o, an ocean current, have to do with the Southern Oscillation, an atmospheric phenomenon?<\/p>\n As well as having a negative impact on the Peruvian fishing industry, El Ni\u00f1o brings rainfall \u2013 sometimes torrential \u2013 to the arid regions of Peru and northern Chile, home to the world\u2019s driest desert, the Atacama. In 1957-1958, a very intense El Ni\u00f1o<\/a> caused torrential rainfall in Peru and other countries, and a severe drought in India and Southeast Asia, spurring further research into the phenomenon. <\/p>\n Read more: In the 1960s, Norwegian-American meteorologist Jacob Bjerknes<\/a> found that the warming of the South American Pacific caused by El Ni\u00f1o was linked to the Southern Oscillation, thereby establishing a close connection between the ocean and the atmosphere. <\/p>\n When the South Pacific tropical anticyclone \u2013 with its associated trade wind pattern that blows from South America towards Australia and Indonesia \u2013 weakens, the waters of the equatorial Pacific warm and begin to shift towards Central America. There they branch off, mainly southwards, along the coasts of parts of Ecuador, Peru and Chile. This is how El Ni\u00f1o is generated. <\/p>\n Bjerknes demonstrated that the atmosphere and the ocean are closely linked, and that what happens in one part of the climate system has an impact elsewhere. Combining the names of the oceanic and atmospheric components gave rise to the El Ni\u00f1o\u2019s official name: El Ni\u00f1o-Southern Oscillation (often abbreviated to ENSO<\/a>).<\/p>\n Sea surface temperature map, with above average temperatures shown in red and below average in blue. The \u2018tongue\u2019 that stretches out to the west of South America is characteristic of El Ni\u00f1o associated heating. This NOAA map from 2016 shows one of the strongest El Ni\u00f1os ever recorded. The worst El Ni\u00f1o of the 20th century<\/p>\n In 1982\u201383, the most intense El Ni\u00f1o of the 20th century<\/a> caused extreme weather events<\/a> throughout the world, including floods in the American Pacific and in the southern United States, and droughts in north-eastern Brazil and Indonesia. It also caused a very mild winter in the mid-latitudes of Europe, Asia and North America. <\/p>\n From that point onward it was observed that, from time to time, temperatures in the equatorial Pacific also showed a negative anomaly, meaning they were lower than normal. At the same time, the South Pacific high-pressure system strengthened, along with the trade winds. This situation was the opposite of El Ni\u00f1o and was named La Ni\u00f1a<\/a>. <\/p>\n In short, El Ni\u00f1o brings warm waters and instability, while La Ni\u00f1a brings colder waters than normal and greater stability to Ecuador, Chile and Peru. These phenomena form recurring cycles, though not over fixed periods of time. <\/p>\n The last intense El Ni\u00f1o of the 20th century occurred in 1997\u201398<\/a>, causing severe flooding in California. It received widespread media coverage, as the disasters occurred in the US. <\/p>\n El Ni\u00f1o can cause severe droughts in some parts of the planet and torrential rain in others. How might the next intense El Ni\u00f1o behave?<\/p>\n![\"A](\"https:\/\/www.newsbeep.com\/il\/wp-content\/uploads\/2026\/06\/file-20260521-57-gwcgni.gif\")
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