Temperatures on the ocean surface have hit a record high, raising fears of another burst of extreme heat this summer.

On 21 June, temperatures outside the polar regions exceeded the extraordinary highs observed at the same time in 2023 and 2024, the Copernicus Climate Change Service said on Wednesday.

It warned the new peak would probably bring “consequences for weather patterns, global climate and marine ecosystems”, not least because it would coincide with the earliest phases of an El Niño eventthey forecast to be the strongest in decades.