The ocean’s temperature reached a record high this June, with global sea surface temperatures at 20.98ºC – and with the El Nino on the way, scientists anticipate that number will only go up.

The news comes from two independent datasets: Copernicus Climate Change Service observed a temperature of 20.86C on 21 June, while the Copernicus Marine Service reported 21.0C on the same day, both higher than previous June records in 2023 and 2024.

The Copernicus report also 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.

The ocean regulates the globe’s climate, absorbing heat from the atmosphere and providing a buffer to the worst impacts of climate change. 

Surface temperatures are affected by solar radiation, water currents and the buildup of heat in the depths. 

The recent European heatwave – described as an event “virtually impossible” without climate change by scientists – is thought to have triggered the rise in water temperatures.

The broader headline also points to some worrying localised trends: in parts of the Mediterranean, experts have recorded local temperature increases of between 6 and 8 degrees Celsius. Temperatures in the North Sea are now around 3°C higher than they were thirty years ago. And, since February, the Belgian coast has experienced a prolonged marine heatwave spanning 144 days.

Global average sea surface temperatures in June were 20.98C, beating the previous records of 2023 and 2024, according to the European Union’s Copernicus Marine Service.

Ocean temperatures can keep the atmosphere warm for longer, provide extra energy to storms, increase evaporation, and enhance the potential for extreme precipitation and flooding. Ocean warming also contributes to sea level rise, ice melt, and added stress on marine ecosystems.

Last year, the ocean reached a troubling new milestone, absorbing more heat last year than at any point since modern records began some 125 years ago.

The research paper – led by the Institute of Atmospheric Physics at the Chinese Academy of Sciences – found that the ocean gained an additional 23 zettajoules of energy in a single year. That is roughly 200 times humanity’s global electricity consumption in 2023 or around 37 years of today’s global energy consumption.

Carlo Buontempo, Copernicus director at the European Centre for Medium-Range Weather Forecasts, warned it could indicate the beginning of a new phase in 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.”

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