Ocean temperatures hit ‘very troubling’ record high

The world’s oceans have reached their highest temperatures on record and are likely to warm even further in the next few months, putting stress on life in the water and on land.

Spurred by a still-growing but already supersized natural El Niño and human-caused climate change, the world’s ocean temperatures hit 21.1 degrees Celsius on Friday and Saturday, narrowly edging out the record set in March 2024, Samantha Burgess, strategic climate lead for European climate service Copernicus, said.

“This is yet another sign of our climate system under strain and the ocean under immense pressure,” Ms Burgess said.

Jane Lubchenco, an oceanographer and former chief of the US National Oceanic and Atmospheric Administration, called the record “very troubling”.

“An ocean this warm destabilises weather patterns and threatens food security, economic prosperity and marine life,” Dr Lubchenco said in an email.

When the ocean warms, it becomes more acidic and carries less oxygen, which hurts food industries that rely on the seas, Ms Burgess said.

She said it also changed ocean currents and weather patterns, giving more juice to storms, making them rainier and making storm surges bigger.

“When we have a warmer ocean such as we’ve had in Europe this summer, it amplifies the impact of heat waves because you don’t get the cooler night-time temperatures with the sea breeze coming off the ocean when the ocean is very warm,” she said.

Normally, because most of the southern hemisphere is ocean, the world’s sea surface temperature peaks in March and April, as the southern summer draws to a close. But this year, the record was set in August, Ms Burgess said.

She said this meant the oceans would keep getting hotter until the current El Niño — a natural, temporary warming of parts of the Pacific that warps weather and raises temperatures globally — reached its peak, which was expected sometime between November and January.

The current El Niño is already as big as recent ones and it is still growing. It is expected to reach unprecedented levels at its peak.

Ms Burgess said it was responsible for a good chunk of the heat in the oceans, alongside long-term warming from burning coal, oil and gas, which had warmed the waters by 0.8C.