Global sea temperatures hit record high in June as scientists warn El Niño could fuel more extreme heat

Global sea surface temperatures reached a record high in June, underscoring the accelerating pace of climate change and raising concerns that the developing El Niño weather pattern could drive even more extreme heat in the months ahead.

According to the European Union’s Copernicus Marine Service, the global average sea surface temperature in June was 20.98°C, surpassing previous June records set in 2023 and 2024.

The milestone capped six months of exceptionally warm oceans in 2026, marked by prolonged marine heatwaves across much of the globe. The average sea surface temperature during the first half of the year stood at 20.04°C, slightly below the record set during the same period in 2024.

Scientists said the emergence of a potentially strong El Niño could push ocean and atmospheric temperatures even higher through the rest of 2026 and into 2027.

“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.

“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 added.

El Niño is a natural climate pattern characterised by unusually warm waters in parts of the Pacific Ocean. It releases additional heat into the atmosphere and alters global weather patterns, increasing the likelihood of floods in some regions and droughts, heatwaves and wildfires in others.

While El Niño can temporarily raise global temperatures, scientists said its effects are being amplified by long-term warming caused by greenhouse gas emissions from burning fossil fuels.

Simon Van Gennip, lead oceanographer at the Copernicus Marine Service, said 2026 is now likely to rank among the warmest years ever recorded.

“This is due to El Niño, but also because of the continued warming caused by greenhouse gas emissions,” he said.

Oceans under growing pressure

The findings come weeks after a major UN scientific assessment warned that the world’s oceans are in a “deepening crisis” as sea temperatures and sea levels continue to rise at accelerating rates.

Oceans absorb around 90% of the excess heat generated by greenhouse gas emissions, making them a critical regulator of Earth’s climate.

Warmer oceans contribute to stronger tropical cyclones, heavier rainfall and rising sea levels through thermal expansion. They also intensify marine heatwaves, placing severe stress on coral reefs and marine ecosystems.

Copernicus said marine heatwaves affected around 82% of the world’s oceans during the first six months of 2026, the second-largest extent on record after 2024.

Mediterranean and Pacific set new records

Among regional hotspots, the Mediterranean Sea recorded its warmest June on record at 24.3°C, surpassing previous highs recorded in 2023 and 2025. Nearly 98% of the basin experienced marine heatwave conditions during the first half of the year.

A marine heatwave in the northwestern Mediterranean reached record intensity earlier this week following an exceptional spell of heat across Europe.

The tropical Pacific also recorded its hottest June ever, with an average sea surface temperature of 27.26°C. The region matched its January-to-June temperature record set in 2016, with particularly strong warming observed in the western equatorial Pacific and waters off Peru and California.