A new study has found that strong El Niño events can cause significant and rapid increases in global mean sea level mainly by shifting large amounts of water from land into the oceans.
Researchers compared the 2014–2016 and 2023–2024 El Niño events. Global mean sea level rose by 9.16 mm during the development phase of the 2014–2016 event and by 7.70 mm during 2023–2024. Water moving from land to the ocean accounted for about 68% and 81% of the respective increases.
The 2023–2024 event produced a faster rise over a shorter period. Warmer ocean waters, particularly in the Indian Ocean also contributed to the increase, with researchers linking the effect partly to the simultaneous positive Indian Ocean Dipole.
Rainfall and runoff patterns across continents also played a major role. A sharp precipitation deficit in South America during 2023–2024 contributed to faster movement of water from land into the ocean.
Scientists are now watching the developing 2026 El Niño closely. According to the report, NOAA gives an 81% chance of a very strong El Niño during October–December, with Niño 3.4 sea surface temperatures potentially exceeding 2°C above average.
A strong 2026 El Niño could therefore accelerate short term sea level rise and further increase global temperatures, potentially contributing to another record hot year.