Global marine heatwaves have become more frequent and longer over the last century

Nature · Published 2 October 2026 Swipe more like this →

In short: Researchers analyzing a century of ocean temperature data found that marine heatwaves are increasing in both frequency and duration. By examining satellite records and various sea-temperature datasets, the study observed that the global average frequency of these extreme events rose by 34% between 1925 and 2016.

The study linked these rising trends to an increase in average ocean temperatures, suggesting that continued global warming may drive further increases in heatwave days. The researchers used a combination of daily satellite imagery, direct in-situ measurements, and monthly gridded datasets to track these changes globally.

Because this was an observational study of historical records, it identifies trends in temperature extremes rather than proving a single direct cause.

Why it matters: Rising ocean temperatures are linked to more frequent and longer-lasting marine heatwaves.

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