El Niños and La Niñas are the third-most dominant influences on Earth's climate, after the sun and the greenhouse effect. But they haven't been easy to decipher or to predict in terms of when they will happen and what exact effects they will have on the global climate.
A new paper compares two recent strong El Niños, their differing effects on globally averaged sea level and the details that distinguished them. The work is published in the Journal of Geophysical Research: Oceans.
El Niños are characterized by warmer-than-usual sea surface temperatures in the Pacific Ocean along the equator, especially in the region called "Niño 3.4." If sea surface temperature anomalies in this region are positive, the state is El Niño; if negative, it is La Niña. Otherwise, the ENSO state (El Niño–Southern Oscillation) is neutral. (Average monthly anomalies for the Niño 3.4 region are published here.)
El Niños elevate global temperatures for their duration; La Niñas lower them. So the impact on global sea level is not surprising. This new research examines how global average sea level responded to the 2014–2016 El Niño and the 2023–2024 El Niño. Both intervals were strong as El Niños go, with sea surface temperature anomalies peaking above 2.0°C. Record global temperatures were seen in 2015 and 2016, and again in 2023 and 2024.
Two processes dominate changes in sea level:
- Steric sea level changes, caused by changes in seawater density primarily due to temperature changes
- Barystatic sea level changes, caused by continental water moving from land and ice to the ocean, or vice versa
Raw sea level data were gathered from Copernicus Marine and Environmental Monitoring Service (CMEMS) and are derived from satellite altimetry, which measures the time a radar or laser signal takes to travel from a satellite to Earth's surface and back.
Another data source comes from Argo buoys that populate the ocean, with adjustments made for ocean bottom deformation and so-called glacial isostatic adjustment—the slow rise and fall of land surfaces once compressed by the weight of ice sheets during the height of the last Ice Age about 23,000 years ago.
Land water drove most of the rise
The four researchers, from two universities in China, found that both El Niños resulted in a rise in global mean sea level (GMSL). In both events, GMSL was driven mostly by barystatic sea level rise, or changes in terrestrial water storage. In the 2023–2024 event, sea level rise was faster and more strongly driven by water from land reaching the ocean, while its steric rise was more concentrated in the Indian Ocean.
In particular, the group found that interannual global average sea level rose by 9.16 mm during the 2014–2016 El Niño development phase and by 7.70 mm during the 2023–2024 phase. In both cases, barystatic sea level dominated the rise: It accounted for about 6.20 mm (68% of the total) in 2014–2016 and 6.26 mm (81%) in 2023–2024. The second event's rise happened over a much shorter period, making the rate of increase much steeper.
The steric sea level rise in the second El Niño was primarily driven by warmer water, especially from the Indian Ocean, the data show. (Changes in salinity also affect steric sea level rise—saltier water is denser and less likely to rise, with the opposite true for fresher water.) "This regional anomaly," the authors wrote, "was likely driven by the simultaneous occurrence of a peak positive Indian Ocean Dipole and El Niño."
The Indian Ocean Dipole (IOD) is a nonperiodic shift in sea surface water temperatures; a positive IOD brings warmer water to the western Indian Ocean. It affects monsoons over the Indian subcontinent and, in its positive phase, causes drought in Indonesia and Australia. A positive IOD also causes more rainfall than normal in eastern Africa, which can increase flooding there. The IOD's interaction with El Niño often leads to stronger El Niños.
Regional rainfall shaped the difference
A significant difference between the two El Niños was the behavior of Africa and North America. Africa saw major terrestrial water loss in 2014–2016, but not in 2023–2024. North America shifted from a small positive barystatic contribution in the earlier event to a strong negative contribution in the latter event.
Why? Precipitation was the main driver of regional terrestrial water storage changes. Runoff in South America was especially important. The 2023–2024 event saw a sharp precipitation deficit over South America, which in turn caused a much faster rate of surface runoff from land and thus more water mass transferred to the ocean.
A strong 2026 El Niño looms
An El Niño has already formed in the tropical Pacific this year, and it is predicted to be a strong one, possibly the strongest ever known. NOAA predicts an 81% chance of a very strong El Niño from October through December 2026. That would mean Niño 3.4 sea surface temperature anomalies above 2.0°C.
It could bring more rapid sea level rise. Global temperatures, already high year-to-date, could be much higher than baseline in late 2026 and might contribute to a new global temperature record in 2026.
Written for you by our author David Appell, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.
Publication details
Zehui Jin et al, Differences and Causes of Interannual Variations of Global Mean Sea Level Between Two El Niño Events in 2014–2016 and 2023–2024, Journal of Geophysical Research: Oceans (2026). DOI: 10.1029/2025jc023533
Who's behind this story?
David Appell is an Oregon-based freelance science writer whose work has appeared in Scientific American, New Scientist, Physics World, and The Washington Post. He holds a Ph.D. in physics from Stony Brook University. Full profile →
BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries. Full profile →
Bachelor's in mathematical biology, Master's in creative writing. Well-traveled with unique perspectives on science and language. Full profile →
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Citation: The impact of recent super El Niños on sea level rise (2026, August 10) retrieved 10 August 2026 from https://phys.org/news/2026-08-impact-super-el-nios-sea.html
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