Ocean surface temperatures hit record high as world enters ‘uncharted territory,’ scientists warn

Temperatures on the ocean surface hit a record high in June, European scientists warned Wednesday, fueling fears of more dangerous heat waves this summer and fanning concerns over the escalating global climate crisis.

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Two separate services under the European Union’s Copernicus Earth observation program — the Copernicus Climate Change Service and the Copernicus Marine Service — announced they had both independently confirmed the record temperatures.

Carlo Buontempo, director of the Copernicus Climate Change Service, warned that the rising temperatures could mark the “beginning of a new phase.”

“With ocean temperatures at these levels and El Niño on the horizon, we are likely to see more temperature records fall in the coming months,” Buontempo said in a statement Wednesday. El Niño is a naturally occurring climate cycle that sees the central and eastern tropical Pacific Ocean become warmer than usual for months at a time.

The world could be heading into “uncharted territory,” Buontempo warned.

According to the Copernicus Climate Change Service and the Copernicus Marine Service, global ocean temperatures outside the polar regions hit record levels on June 21, surpassing levels for the time of the year observed in both 2023 and 2024.

The Copernicus Climate Change Service said temperatures reached 20.86 degrees Celsius (69.54 degrees Fahrenheit) that day, climbing above the 20.83 C (69.49 F) observed in 2023 and 2024.

The Copernicus Marine Service, meanwhile, recorded temperatures at 21 C (69.8 F), beating records from 2023 and 2024 by 0.1 degree Celsius.

“It’s consistent with what we’ve known for a long time — that the planet is warming because we’re emitting vast quantities of greenhouse gases, primarily from fossil fuel burning, into the atmosphere and that’s stifling the ability of the planet to lose its heat to space,” Richard Allan, a professor of climate science at the University of Reading in the U.K., said in a phone interview.

Oceans absorb around 90% of the excess energy on Earth, which is primarily caused by the burning of fossil fuels like oil, coal and gas, with rising temperatures painting a concerning picture of the impacts of climate change and the “emerging influence of El Niño” also a factor, Allan said.

It is important to continue using the tools available to monitor rising ocean surface temperatures and to “adapt” in parallel and “reduce our green gas emissions,” oceanographer Pierre-Yves Le Traon said.

“It’s really worrying to see this trend,” said Le Traon, the scientific director of Mercator Ocean International, a research institute based in Toulouse, France, which operates the Copernicus Marine Service.

The announcements came as a dangerous heat wave looked set to scorch parts of the United States ahead of the July Fourth weekend. More than 46 million people across the country were under extreme heat alerts as of Wednesday, according to the National Weather Service.

The weather service warned of “dangerous heat” set to build across the central and eastern U.S., with highs expected to reach the mid-to-upper 90s and some locations exceeding 100 F.

Areas across the Ohio Valley, the mid-Atlantic and into the Northeast were expected to see record-breaking high temperatures through Thursday, it warned, with parts of northern neighbor Canada also facing extreme heat.

Meanwhile, heat records were broken across Europe last week, with World Health Organization chief Tedros Adhanom Ghebreyesus warning that more than 1,300 excess deaths had been recorded since June 21 “linked to high temperatures in Europe.”

France’s national health ministry said Sunday that there had been around 1,000 more deaths in the week before than expected in the country amid its record-smashing heat wave.

“Driven by climate change and global warming, the phenomenon of the ‘once-in-a-generation’ heat wave is now occurring nearly annual,” Tedros said in a post on X on Sunday. Europe, he noted, is the “fastest-warming continent on the Earth, heating at twice the global average,” with European homes, workplaces and schools “not built for these temperatures.”