World's Oceans Reach Highest Recorded Temperature Amid Growing El Niño

On August 22 and 23, 2026, the world's oceans reached their highest surface temperature ever recorded outside polar regions, hitting an average of 21.1 degrees Celsius (70 degrees Fahrenheit), according to data from the European Copernicus Climate Change Service (C3S).

This new record surpasses previous highs recorded in March 2024 and comes unusually late in the year, as ocean temperatures typically peak in March or April after the southern hemisphere summer.

The rising ocean temperatures are driven by a combination of long-term human-induced climate warming and a rapidly intensifying El Niño event, which is projected to become the strongest in at least a century, affecting global weather patterns and marine ecosystems.

Dr. Samantha Burgess, deputy director of Copernicus, highlighted the ocean's growing stress, stating, "El Niño is adding heat to the system, but it is doing so on top of decades of human-driven warming." She noted that marine heatwave days worldwide have more than tripled since the early 1990s.

The heat increase contributes to sea level rise through thermal expansion and fuels extreme weather by transferring more energy and moisture to the atmosphere, raising risks for coastal communities and low-lying nations.

Jane Lubchenco, oceanographer and former chief of the U.S. National Oceanic and Atmospheric Administration, called the record "very troubling," emphasizing that "an ocean this warm destabilizes weather patterns and threatens food security, economic prosperity and marine life." She added, "A warmer ocean is not our friend."

Marine ecologists warn of significant impacts on marine life and fisheries. John Bruno, University of North Carolina marine ecologist, expressed concern over warming effects on coral reefs and fisheries, noting, "The amount of heat sensitive coral alive today is about one-fifth of 1990s levels." He also mentioned adaptive responses among some coral species but cautioned about ongoing risks.

Boris Worm, biology professor at Dalhousie University, warned about fisheries collapse, especially the Peruvian anchovy fishery, which is vulnerable during El Niño events. He explained, "When the water gets hot, larger creatures can swim to cooler water, but anchovies can't leave so they just don't reproduce or starve." He added that this disruption affects the entire marine food web and human communities dependent on it.

Warmer oceans also reduce oxygen levels and increase acidity, harming marine ecosystems and industries dependent on the sea. Burgess noted the increased presence of jellyfish in warmer waters off Europe, a trend also observed on the U.S. East Coast.

Dr. Jeremy Grist, senior research fellow at the National Oceanography Centre, said the early breaking of ocean temperature records signals the strength of the El Niño event, predicting the record may be broken again by March or April 2027.

Scientists caution that continued warming threatens marine biodiversity and intensifies weather extremes, underscoring the need for urgent climate action and protection of marine ecosystems.