El Niño/Southern Oscillation

atmospheric phenomenon

Also known as: ENSO

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 23, 2026

Quick Summary

The El Niño/Southern Oscillation (ENSO) is a climate pattern characterized by fluctuations in sea surface temperatures and atmospheric pressure across the tropical Pacific Ocean. It has two main phases: El Niño, marked by warmer-than-normal sea surface temperatures in the eastern Pacific, and La Niña, characterized by cooler-than-normal temperatures.1234

These shifts in ocean temperatures influence global weather patterns, leading to varied effects such as droughts in some regions and increased rainfall in others. ENSO events occur irregularly, typically every two to seven years, and can have significant impacts on ecosystems, agriculture, and weather worldwide.124

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

4 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

Australia
Climate
…negative phases are related to El Niño episodes in the South Pacific, and most of Australia’s major droughts have been related to those episodes. Prolonged positive SOI phases (during La Niña) normally bring above-average rainfall and floods to eastern and northern Australia. In each case, however, the correlations are not…
Read More
…negative phases are related to El Niño episodes in the South Pacific, and most of Australia’s major droughts have been related to those episodes. Prolonged positive SOI phases (during La Niña) normally bring above-average rainfall and floods to eastern and northern Australia. In each case, however, the correlations are not…
Read More

global warming
Regional predictions
of El Niño/Southern Oscillation (ENSO) events will adjust to climate change. Since ENSO is one of the most prominent sources of interannual variations in regional patterns of precipitation and temperature, any uncertainty in how it will change implies a corresponding uncertainty in certain regional patterns of climate change. For…
Read More
of El Niño/Southern Oscillation (ENSO) events will adjust to climate change. Since ENSO is one of the most prominent sources of interannual variations in regional patterns of precipitation and temperature, any uncertainty in how it will change implies a corresponding uncertainty in certain regional patterns of climate change. For…
Read More

Southern Oscillation
…the El Niño/Southern Oscillation (ENSO). The phase of the Southern Oscillation at a given point in time may be understood using the Southern Oscillation Index (SOI), which compares the difference in atmospheric pressure over Australia and Indonesia with that of the eastern South Pacific.
Read More
…the El Niño/Southern Oscillation (ENSO). The phase of the Southern Oscillation at a given point in time may be understood using the Southern Oscillation Index (SOI), which compares the difference in atmospheric pressure over Australia and Indonesia with that of the eastern South Pacific.
Read More

weather
…scientists call the El Niño/Southern Oscillation (ENSO). It is believed that ENSO is responsible not only for unusual weather events in the equatorial Pacific region (e.g., the exceedingly severe drought in Australia and the torrential rains in western South America in 1982–83) but also for those that periodically occur…
Read More
…scientists call the El Niño/Southern Oscillation (ENSO). It is believed that ENSO is responsible not only for unusual weather events in the equatorial Pacific region (e.g., the exceedingly severe drought in Australia and the torrential rains in western South America in 1982–83) but also for those that periodically occur…
Read More