El Niño–Southern Oscillation

El Niño–Southern Oscillation is a recurring climate fluctuation linking tropical Pacific sea-surface temperatures with atmospheric pressure and winds. Its warm El Niño and cool La Niña phases alter weather patterns worldwide.

Walker circulation: An east–west atmospheric circulation over the tropics driven by temperature differences between ocean regions. Its strength and position shift as tropical Pacific temperatures change.
El Niño: The warm phase of ENSO, marked by unusually warm sea-surface temperatures in the central and eastern equatorial Pacific. It is the warm-ocean phase of the coupled fluctuation.
Seasonal climate prediction: Forecasting average climate conditions over periods of months to about a year. ENSO supplies a major source of predictability for seasonal rainfall and temperature.
1982–1983 El Niño: A very strong El Niño event spanning 1982 and 1983, associated with widespread climatic disruptions. It demonstrated the global reach of a major event before satellite monitoring was mature.
Teleconnection: A statistical or physical connection between climate variations in widely separated regions. ENSO is a leading source of recurring climate links between the tropics and distant regions.
Trade winds: Persistent easterly winds that blow across the tropics toward the equator. Their weakening helps warm water spread eastward during El Niño.
La Niña: The cool phase of ENSO, marked by unusually cool sea-surface temperatures in the central and eastern equatorial Pacific. It is the cool-ocean phase of the coupled fluctuation.
Drought: A prolonged period of unusually low water availability caused by deficient precipitation or other factors. ENSO shifts the odds of drought in regions including Australia and southern Africa.
1997–1998 El Niño: A very strong El Niño event spanning 1997 and 1998, marked by exceptional tropical Pacific warming. Its extensive observations helped document a powerful event across ocean and atmosphere.
North Atlantic Oscillation: A fluctuation in atmospheric pressure differences over the North Atlantic that affects regional winds and weather. ENSO can influence North Atlantic circulation, though the relationship varies.

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