This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: El Niño is part of a natural climate pattern that occurs roughly every two to seven years, bringing warmer-than-normal water to parts of the equatorial Pacific. The most recent very strong El Niño events, in 1997–98 and 2015–16, upended weather patterns.
Impacts spanned the planet, from fires in Indonesia and the Amazon to crop failures due to drought in southern Africa to heavy rain and coastal flooding in Southern California. The current El Niño rivals these past heavyweights. Every El Niño grows from a feedback loop between the atmosphere and the ocean.
Trade winds normally keep warm water piled up in the western Pacific, where it stands higher than in the east. When those winds weaken, that warm water begins to pulse eastward, which further weakens and sometimes reverses the winds, allowing even more warm water to move east. The cycle intensifies as waters continue to warm and pile up in the central and eastern Pacific.
But each El Niño has its own character, shaped by where in the Pacific the warmth builds and how the atmosphere responds. "The search for the 'typical' El Niño is very elusive," said Josh Willis, project scientist for sea level missions at NASA's Jet Propulsion Laboratory (JPL). "They're all different in terms of where they land and how their impacts play out." Altimetry satellites can track those differences by measuring the height of the sea surface.
Because water expands as it warms, higher-than-normal sea levels in the central and eastern equatorial Pacific signal the buildup of heat associated with El Niño. The maps above depict sea surface height anomalies across the Pacific Ocean on Oct. 13, 1997 (left), and on Oct. 12, 2026 (right). Data are from the TOPEX/Poseidon satellite and the Sentinel-6 Michael Freilich satellite, respectively, and were processed by scientists at JPL.
Shades of red indicate where sea levels were higher than average. Normal sea level conditions appear white, and lower areas are blue. Signals related to seasonal cycles and long-term trends have been removed to highlight sea level anomalies associated with El Niño and other short-term natural phenomena.
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