Global Ocean Temperatures Are Now Hotter Than Ever — With Far-Reaching Consequences For The Planet

By Sam Meredith

The world’s ocean temperatures have climbed to their hottest level on record, according to data from the European Union’s climate monitor, prompting scientists to warn of immediate and wide-ranging consequences for the planet.

The average daily global sea surface temperature rose to 20.98 degrees Celsius (69.76 Fahrenheit) on Aug. 4, according to the latest data from the EU’s Copernicus Climate Change Service, far above the average for this time of year.

The average surface temperature of the world’s oceans hit 20.96 degrees Celsius in late July, surpassing a previous record logged in 2016, before gradually rising closer to 21 degrees on each of the first four days of August. Copernicus data stretches back to 1979.

The surface temperature of the world’s oceans would typically be expected to reach its highest in March rather than in August, sparking alarm among climate scientists.

“The recent ocean warming is genuinely concerning,” said Rowan Sutton, professor of climate science at the University of Reading.

Sutton said that the latest sea surface temperature data showed that “we may be experiencing not just a record-breaking extreme event but a record-shattering one.”

“This is yet another alarm bell that screams out for the most urgent actions to limit future warming and to adapt to the serious changes that are unfolding before our eyes,” he added.

The ocean heat record comes as part of a recent trend of extreme heat stretching across the globe, with this July poised to be recognized as the hottest month in history.

The world’s oceans are a critical life support system and a vital buffer against the impacts of the climate crisis. The ocean generates 50% of the planet’s oxygen, absorbs 25% of all carbon dioxide emissions and captures 90% of the excess heat produced by said emissions, according to the U.N.

Ever-increasing greenhouse gas emissions have affected the health of the ocean, and scientists have repeatedly issued warnings about the potential changes to life underwater and on land.

“The deeper oceans have been warming for decades due to climate change and shifting circulation patterns have likely brought some of that heat to the surface,” said Piers Forster, professor of physical climate change at the University of Leeds.

“The ocean heatwave is an immediate threat to some marine life, we are already seeing coral bleaching in Florida as a direct result, and I expect more impacts will surface,” Forster said.

Kaitlin Naughten, an ocean modeler from the British Antarctic Survey, said it is clear from the Copernicus data that current sea surface temperatures were “exceptionally and unseasonably warm.”

She added that the combination of the climate emergency and El Niño means humanity can expect temperature records like this to occur “more and more frequently” in the future. “A warm sea surface has wide-ranging implications, especially for complex ecosystems such as coral reefs,” Naughten said.

Daniela Schmidt, professor in the School of Earth Science at the University of Bristol, said the rapid warming of the oceans could not yet be attributed to the El Niño phenomenon — a naturally occurring climate pattern that contributes to higher temperatures across the globe. The U.N. weather agency declared the onset of El Niño on July 4., warning its return could pave the way for extreme weather conditions.

“People tend to forget that when the water gets hot, most organisms in the sea need much more food for their basic function.

And what happens if they grow less or calcify less? It will have impacts for their future with fewer offspring or weaker protection by their shells and skeletons,” Schmidt said.

“We have no time left to deal with this problem in the future. Any further delay will just make the problem so much worse.”