Average global sea-surface temperature outside the polar regions reached a record 21.1°C on Saturday, according to the European Union’s Copernicus Climate Change Service. The reading slightly exceeded the previous 21.09°C record registered for three days in March 2024. Scientists said the timing is particularly concerning because the new record was set in August, whereas global ocean temperatures usually peak in March or April.

The record has occurred before the strengthening El Niño reaches its maximum intensity. El Niño brings unusually warm water to the surface in the central and eastern equatorial Pacific, raising global average temperatures. Copernicus deputy director Samantha Burgess said the record was a clear signal of mounting pressure on the oceans, with El Niño adding heat to a system already warmed over decades by human activity.

Scientists said El Niño could strengthen until around Christmas and warned it may be heading toward one of the strongest events in several centuries. Marine heatwaves are also affecting waters near Europe, while warmer seas can intensify storms, increase coastal flood risks and damage marine ecosystems, including coral reefs.