Oceans hit highest temperature on record

Data indicates that the planet's oceans have just recorded their warmest temperature ever measured. The European Copernicus climate change service reported that the average surface temperature of the seas outside the polar regions reached 21.1C (70F) on Saturday. This temperature surpasses the previous peak of 21.09C, which was recorded on multiple days in March 2024, and is significantly above the average for this time of year.

Dr Samantha Burgess, deputy director of Copernicus, stated that this record underscores an ocean experiencing growing stress. The El Niño phenomenon is further exacerbating the situation, adding heat to a system already under pressure from human-driven warming. The data, which reflects sea temperatures 10 meters below the surface, was gathered from buoys, ships, and satellites and used to estimate global ocean temperatures.

While the current record is still modestly narrow and the global estimate carries uncertainties, the timing is particularly alarming. Usually, global sea temperatures peak in March or April, corresponding to the end of summer in the southern hemisphere, which holds a larger portion of the planet's ocean surface and thus a stronger influence on average temperatures.

The urgency is heightened by the fact that the oceans are already exceptionally warm even before the expected peak of the El Niño weather event. El Niño typically intensifies until Christmas, potentially causing further temperature increases. While the western English Channel has been experiencing unusually warm conditions for over three years, the waters worldwide are also considerably warmer than usual.

This widespread warmth is a clear indication of the significant impact of human-induced climate change on the oceans. The latest Copernicus data underscores the troubling upward trend in ocean temperatures. As warmer seas fuel more extreme weather, they can intensify storms, extend heatwaves on land, and raise sea levels, increasing the risk of coastal flooding and severely affecting marine ecosystems and the communities that depend on them.