World’s oceans experience hottest June ever, scientists say more heat ahead

The world’s oceans experienced their “warmest June ever observed” and could see further record-breaking highs in the months ahead as El Niño and climate change push temperatures higher, according to a new report.

The European Union’s Copernicus Marine Service said on Wednesday that “record global sea surface temperatures” of 21.0 degrees Celsius (69.8 degrees Fahrenheit) in June beat the previous records in the same month in 2023 and 2024.

“The first six months of 2026 were characterised by persistently elevated sea-surface temperatures and widespread marine heatwaves across much of the global ocean,” the EU’s marine environment monitor said in a statement.

“Marine heatwaves expanded steadily throughout the period, ultimately affecting around 82 percent of the global ocean,” said Simon van Gennip, lead oceanographer for the Copernicus Marine Service.

“The Mediterranean, the central North Atlantic and the equatorial Pacific all emerged as hotspots, and these regional signals paint a consistent picture of an ocean under sustained thermal stress,” Van Gennip said in a statement.

The onset of a potentially powerful El Nino weather pattern could boost global heat in the oceans and atmosphere even further in 2026, and into next year, according to scientists.

“Current conditions could indicate the beginning of a new phase, leading, once more, to uncharted territory,” said Carlo Buontempo, director of the Copernicus Climate Change Service, the EU’s climate monitor.

“With ocean temperatures at these levels and El Nino on the horizon, we are likely to see more temperature records fall in the coming months,” Buontempo said in a statement.

El Nino is marked by unusually warm waters in parts of the Pacific Ocean, releasing more heat into the atmosphere and influencing wind, cloud and weather patterns around the globe. This can raise the risk of weather extremes, ranging from floods in Peru to droughts in parts of Africa and wildfires in Australia.

Land and sea temperatures reached an all-time high in 2024 at the tail end of the last El Nino, and 2026 could be among the warmest years recorded with the onset of the next El Nino this year.

The Copernicus report follows a warning issued in a major UN scientific assessment last month, which declared that the world’s oceans were in a “deepening crisis” as seas were warming and rising faster.

Oceans are a key regulator of Earth’s climate because they absorb some 90 percent of the excess heat caused by humanity’s release of greenhouse gases, such as carbon dioxide.

Warmer oceans increase moisture in the atmosphere, providing fuel for tropical cyclones and destructive rainfall.

Hotter seas also directly contribute to sea-level rise – water expands when it warms up – and create unbearable conditions for tropical reefs, whose corals can bleach and die during prolonged marine heatwaves.