El Niño is making days on Earth slightly longer
As El Niño intensifies, changes in global wind patterns are slightly slowing Earth’s rotation, adding about 1 millisecond to the length of a day at the peak of a strong event.
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El Niño is doing more than changing the weather. It is also making days on Earth slightly longer.
As El Niño intensifies across the Pacific Ocean, the large-scale climate pattern can cause Earth to rotate a little more slowly. “The change, however, is only about 1 millisecond at the peak of a strong El Niño,” NOAA explained.
One millisecond is one-thousandth of a second, large enough for scientists to measure but far too small for people to notice in their everyday lives. With 86,400 seconds in a day, the difference amounts to roughly one part in 100 million.
How can El Niño alter the rotation of the entire planet?
El Niño is associated with major wind patterns around the globe. Trade winds across the tropical Pacific weaken, while west-to-east winds farther from the equator strengthen. Those changes redistribute angular momentum, essentially the rotational energy shared between Earth and its atmosphere. To keep the overall system in balance, Earth’s rotation slows slightly.
A satellite picture of the Earth on Oct. 19, 2026. (NOAA/GOES-East)
The principle is similar to a spinning ballerina. When a ballerina pulls their arms closer to their body, they spin faster. Extending their arms outward has the opposite effect.
When the Pacific shifts in the opposite direction, Earth can respond accordingly.
“La Niña tends to have the opposite effect,” NOAA said. That means Earth’s rotation can speed up slightly during La Niña, making days marginally shorter.
El Niño is not the only natural phenomenon capable of altering the length of a day. NASA says changes in the atmosphere, oceans, groundwater and ice can all affect Earth’s rotation over different timescales. "Our seasonal and daily weather variations can affect the length of day by a few milliseconds over a year," NASA added.
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