Name and discovery
In the 19th century, Peruvian fishermen called a warm current that arrived around Christmas and drove away anchovies El Niño, after the Christ child. In the 1920s Gilbert Walker, head of the India Meteorological Department, tried to forecast monsoon failures. He found the Southern Oscillation, a seesaw in air pressure between the eastern and western Pacific. In 1969 Norwegian-born meteorologist Jacob Bjerknes showed that El Niño and the Southern Oscillation are one coupled ocean–atmosphere phenomenon, now called ENSO. After nobody predicted the 1982–83 El Niño, the US deployed a buoy network across the equatorial Pacific.
Mechanism and La Niña
Normally, east-to-west trade winds push warm surface water toward Indonesia, and cold deep water wells up off South America. When the trade winds weaken, warm water spreads east and El Niño develops, with the main rain belt shifting east as well. La Niña ("the girl") is the opposite: stronger trade winds and a cooler-than-normal eastern Pacific. NOAA declares El Niño when temperatures in the Niño 3.4 region stay at least 0.5°C above normal.
Global impacts
El Niño tends to bring flooding to Peru and Ecuador, drought and wildfires to Indonesia and Australia, and a weaker Indian monsoon. It can push up prices of coffee, cocoa, and rice. In the US it often means a wetter South and a milder North in winter. It also lifts global average temperatures temporarily. Strong events in 1998, 2016, and 2023–24 set record highs, especially on top of warming from the greenhouse effect. Warmer seas, together with ocean acidification, also worsen coral bleaching.
FAQ
- Does El Niño mean a mild winter?
- In the northern US it often does, but other factors such as Arctic outbreaks can override it.
- Is climate change making El Niño more frequent?
- Some studies suggest strong events may become more common, but there's no consensus yet.
Sources reviewed: 2026-10-26
References
- Bjerknes, J. (1969). Atmospheric teleconnections from the equatorial Pacific. Monthly Weather Review, 97(3), 163–172.
- Walker, G. T. (1924). Correlation in seasonal variations of weather IX. Memoirs of the Indian Meteorological Department, 24, 275–332.
- NOAA Climate Prediction Center. ENSO: Recent Evolution, Current Status and Predictions.