Global ocean surface temperatures hit record high, alarming scientists

The world's oceans have reached their highest recorded temperatures, according to the European climate service Copernicus. The global average sea surface temperature hit 21.1 degrees Celsius over the weekend, narrowly surpassing the previous daily record set in March 2024.

Samantha Burgess, strategic climate lead for Copernicus, said the record is "another sign of our climate system under strain and the ocean under immense pressure." The warming is attributed to a growing El Nino event and long-term human-caused climate change.

Jane Lubchenco, a former chief of the U.S. National Oceanic and Atmospheric Administration, called the record "very troubling," noting that a warmer ocean destabilizes weather patterns and threatens food security and marine life.

Warmer oceans become more acidic and hold less oxygen, which can harm fisheries. They also influence weather patterns, potentially intensifying storms and storm surges. Burgess noted that warm seas can amplify heatwaves, as seen in Europe this summer, by reducing the cooling effect of sea breezes at night.

Typically, global sea surface temperatures peak in March or April, but this year's record was set in August. The ocean is expected to warm further as El Nino reaches its peak, predicted between November and January.

Scientists expressed concern about the potential impacts on marine ecosystems. Boris Worm, a biology professor at Dalhousie University, said the early onset of such extreme warmth is "out-of-normal" and that "the ocean is not supposed to do this."

John Bruno, a marine ecologist at the University of North Carolina, warned of potential fisheries collapse and food shortages, particularly in the Peruvian anchovy fishery, which is vulnerable during El Nino events. He also noted that while some coral species are adapting to warmer water, the overall outlook remains worrying.

Warmer waters may also lead to an increase in jellyfish populations, which thrive in warm conditions. Rick Spinrad, another former NOAA chief, said the ocean acts as the planet's thermostat, and these record temperatures portend greater challenges ahead.