June Sets New Ocean Heat Record as Global Sea Surface Temperature Reaches 20.98°C

The world’s oceans recorded their hottest June ever in 2026, with global average sea surface temperatures reaching 20.98°C, according to the European Union’s Copernicus Marine Service.

Scientists warned that temperatures could climb even higher in the coming months as the developing El Niño weather pattern combines with long-term climate change.

The June average surpassed the previous records set in 2023 and 2024, capping six months of exceptionally warm oceans. The average sea surface temperature for the first half of 2026 stood at 20.04°C, making it one of the warmest January-to-June periods on record.

Researchers said the emergence of El Niño—a climate pattern marked by unusually warm waters in the Pacific Ocean—could push both ocean and atmospheric temperatures to new highs later this year 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.

He added that with ocean temperatures already at record levels and El Niño developing, more temperature records are likely to fall in the months ahead.

El Niño, climate change driving warming

El Niño releases additional heat from the Pacific Ocean into the atmosphere, altering global weather patterns and increasing the likelihood of extreme events such as floods, droughts and wildfires. It can also temporarily boost global temperatures, adding to the long-term warming driven by greenhouse gas emissions.

According to Simon Van Gennip, Lead Oceanographer at the Copernicus Marine Service, the combination of El Niño and continued greenhouse gas emissions is expected to make 2026 one of the warmest years ever recorded.

Oceans under mounting pressure

The findings come weeks after a major UN scientific assessment warned that the world’s oceans are facing a “deepening crisis”, with warming and sea-level rise accelerating.

Oceans absorb nearly 90% of the excess heat trapped by greenhouse gas emissions, making them a critical regulator of Earth’s climate. However, rising sea temperatures also intensify tropical cyclones, increase heavy rainfall, contribute to sea-level rise through thermal expansion and trigger coral bleaching during prolonged marine heatwaves.

Marine heatwaves spread across the globe

The first half of 2026 witnessed widespread marine heatwaves covering around 82% of the world’s oceans, the second-largest extent on record after 2024.

Marine heatwaves are prolonged periods of unusually high ocean temperatures that can disrupt marine ecosystems, damage coral reefs and affect fisheries and weather patterns.

Among the worst-hit regions was the Mediterranean Sea, where the average June sea surface temperature reached a record 24.3°C, surpassing previous highs recorded in 2023 and 2025. Nearly 98% of the Mediterranean basin experienced marine heatwave conditions during the first six months of the year.

The tropical Pacific Ocean also recorded its warmest June on record at 27.26°C, with particularly persistent warming observed in the western equatorial Pacific and off the coasts of Peru and California, reinforcing expectations of a strengthening El Niño in the months ahead.