Multiple international media outlets reported on the 24th that data from the EU's Copernicus Climate Change Service revealed the average sea surface temperature in non-polar regions hit 21.1°C on August 22nd, setting a new all-time record. This reading slightly surpasses the 21.09°C record set on three separate dates in March 2024 and significantly exceeds the average for this time of year. Ryan Katz-Rosenthal, a professor at the University of Ottawa, wrote on X: "This could even be the warmest sea surface temperature since the last interglacial period 125,000 years ago."

What makes this even more unusual is that the record was set in August. Global ocean temperatures typically reach their annual peak in March or April, following the end of the southern hemisphere summer, and usually begin to cool by August. Experts believe this historic high occurring during such an atypical period highlights the severe trend of continuous ocean warming. "This record once again clearly demonstrates the increasing pressure on our oceans," Samantha Burgess, Deputy Director of the Copernicus Climate Change Service, told the BBC. El Niño is injecting additional heat into the climate system, but this effect is built upon decades of global warming caused by human activities.

Sea surface temperature data is collected using buoys, ships, and satellites measuring water temperature approximately ten meters below the surface, with global estimates derived from a combination of these measurements. Data from the National Oceanic and Atmospheric Administration cited by The Washington Post shows that 42% of the world's oceans are currently experiencing marine heatwaves, with the Pacific Ocean alone seeing heatwave coverage equivalent to nine times the size of the contiguous United States, greatly contributing to the new global sea surface temperature record.

The BBC reported that waters around the UK and Europe have also been experiencing abnormally high temperatures. According to data from the Plymouth Marine Laboratory, the western English Channel has been in a state of nearly continuous marine heatwave for over three years, with local sea temperatures in July 2026 temporarily reaching 7°C above normal levels. What concerns scientists even more is that this new sea temperature record was set before El Niño has reached its expected peak. According to the latest forecast from China's National Climate Center last week, current sea surface temperatures in the central and eastern equatorial Pacific continue to rise, and are expected to reach their peak around November or December this year, potentially forming a super El Niño event that could be the strongest on record.

Jeremy Grist, a senior researcher at the UK's National Oceanography Centre, told the BBC that the sea temperature breaking records at this time is an early signal of the intensifying El Niño. "If other conditions remain unchanged, the global ocean temperature record could be broken again in March or April 2027."

Rising sea temperatures could trigger a series of chain reactions, providing more moisture and energy for storms, thereby increasing the risk of heavy rainfall and severe storm intensification, and raising the likelihood of flooding and storm surge disasters in coastal areas. In some coastal regions, warmer seawater can also weaken the cooling effect of sea breezes, further exacerbating heatwaves on land. Persistent or intense marine heatwaves can also damage important habitats such as coral reefs and seagrass beds, threatening fishery resources and coastal communities that depend on the ocean for their livelihoods.

Oceans are the most important heat storage reservoir in the Earth's climate system. Scientists estimate that more than 90% of the excess heat generated by human greenhouse gas emissions is absorbed by the oceans. However, as the Guardian cited scientists' analysis, rising ocean temperatures reduce the efficiency of carbon dioxide absorption, which could weaken one of the planet's most important natural buffers against global warming.