Rare ‘triple-dip’ La Niña may explain why 2023 was so hot
The record-breaking global temperatures seen in late 2023 may have emerged partly because of unusual conditions in the Pacific Ocean in the preceding years
By Madeleine Cuff
18 August 2025
The Pacific Ocean released heat into the atmosphere in 2023
blickwinkel/Alamy
An unusual “triple dip” La Niña that suppressed ocean temperatures in the Pacific Ocean for three years running may have primed the planet for the dramatic surge in global heat experienced in 2023.
While global temperatures had been expected to increase around this time, due in part to greenhouse gas emissions and warm surface waters in the Pacific, they weren’t anticipated to peak until early 2024. As it was, record-breaking heat emerged from September 2023, months ahead of schedule.
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Something strange is happening in the Pacific and we must find out why
Julius Mex at the University of Leipzig in Germany and his colleagues set out to explore what exactly happened in late 2023 to trigger the onset of this extraordinary heat. “What we’re trying to explain is why the change in temperature in boreal fall was so extreme,” he says.
The team used datasets that combine historical weather observations with climate models to investigate circulation, temperature, cloud cover, radiation and precipitation in the Pacific during 2022 and 2023.
They conclude that the background state of the Pacific, which unusually had been stuck in cooler La Niña conditions since 2020, was a key factor. That suppressed ocean heat and encouraged the development of low-lying clouds, helping to reflect more of the sun’s radiation back into space.
