El Niño Southern Oscillation (ENSO)


The connection between Earth’s oceans and atmosphere has a direct impact on the weather and climate conditions we experience. El Niño and La Niña, together called the El Niño Southern Oscillation (ENSO), are periodic departures from expected sea surface temperatures (SSTs) in the equatorial Pacific Ocean. These warmer or cooler than normal ocean temperatures can affect weather patterns around the world by influencing high and low pressure systems, winds, and precipitation. ENSO may bring much needed moisture to a region while causing extremes of too much or too little water in others.

El Niño

El Niño Warmer than normal tropical Pacific sea surface temperatures.

La Niña

La Niña Cooler than normal tropical Pacific sea surface temperatures.
drought flooding coral bleaching
ENSO impacts can include hazards to people and property from droughts, heatwaves, and floods. Ecosystems are also at risk, for example corals may become bleached by distress from unusually warm ocean temperatures.
Understanding the processes driving these types of interactions is a key component in improving forecasts and warnings. The ESRL Physical Sciences Division studies multiple aspects of ENSO including its precursors, prediction, diversity, and climate and ecosystem impacts. This information can help keep communities safe and guide decisions related to issues such as water managagement, emergency planning, and ecosystem resilience.
The following pages contain information, tools, and resources we hope you will find useful in broadening your understanding of ENSO.

What's New?

Animation showing average sea surface temperature anomalies over the past year. Updated weekly. (Larger View)
Video on potenial impacts of El Niño in Colorado.