The world’s oceans just had their hottest June on record

The world’s oceans recorded their hottest June on record, with scientists warning that a strengthening El Niño event, combined with human-driven climate change, could push global temperatures into “uncharted territory” in the coming months.

According to the European Union’s Copernicus Marine Service, global average sea surface temperatures reached 21.0 degrees Celsius (69.8°F) in June, surpassing previous records for the month set in 2023 and 2024.

The monitoring agency said the first half of 2026 was marked by persistently high sea surface temperatures and widespread marine heatwaves across much of the world’s oceans.

“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 service said in a statement.

Marine heatwaves steadily expanded during the period, affecting about 82 per cent of the global ocean, according to Simon van Gennip, lead oceanographer at the Copernicus Marine Service.

“Marine heatwaves expanded steadily throughout the period, ultimately affecting around 82 percent of the global ocean. 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.

The new record surpassed the unusually high ocean temperatures recorded in June 2023, which scientists at the time described as unprecedented and which preceded a devastating period of global heatwaves, floods and storms associated with El Niño.

Scientists said it remains too early to determine whether this year’s warming will continue to intensify, as sea surface temperatures typically peak in July and August. However, they warned that the emergence of what could become one of the strongest El Niño events in decades raises the likelihood of further record-breaking temperatures.

Carlo Buontempo, director of the Copernicus Climate Change Service, said current conditions could signal another period of exceptional global heat.

“Current conditions could indicate the beginning of a new phase, leading, once more, to uncharted territory. With ocean temperatures at these levels and El Niño on the horizon, we are likely to see more temperature records fall in the coming months,” he said.

El Niño is a naturally occurring climate pattern marked by unusually warm waters in the central and eastern Pacific Ocean. It releases additional heat into the atmosphere and alters global weather patterns, increasing the risk of floods in some regions, droughts in others and more intense wildfires.

The report comes just weeks after a major United Nations scientific assessment warned that the world’s oceans are facing a “deepening crisis” as ocean warming and sea level rise continue to accelerate.

Oceans play a crucial role in regulating Earth’s climate by absorbing about 90 per cent of the excess heat generated by greenhouse gas emissions from burning fossil fuels such as coal, oil and gas.

As oceans warm, they transfer more moisture into the atmosphere, increasing the likelihood of stronger tropical cyclones, heavier rainfall and other extreme weather events. Rising ocean temperatures also contribute to sea level rise through thermal expansion and place additional stress on coral reefs, which can bleach and die during prolonged marine heatwaves.

Scientists say continued monitoring over the next two months will determine whether 2026 follows the trajectory of 2023, when exceptionally warm oceans contributed to one of the hottest periods ever recorded globally.