BEIJING (dpa): The heat content of the world's oceans up to a depth of 2,000 metres reached a new record in 2025, the highest level since measurements began and the ninth consecutive year of warming, according to an analysis by an international group of scientists.
They found in a study released on Friday that the thermal energy increased by 23 quadrillion megajoules in 2025 compared to 2024, reported German news agency dpa.
A team led by Lijing Cheng from the Chinese Academy of Sciences in Beijing published their research findings with data since 1958 in the journal "Advances in Atmospheric Sciences."
In terms of average global sea surface temperatures, 2025 was the third warmest year after 2024 and 2023.
The researchers explain the difference depth and surface temperatures by stating that the climate phenomenon El Niño in the Pacific Ocean weakened significantly over the past year.
The El Niño phase is regularly associated with higher global temperatures at the sea surface.
When considering heat content, temperatures in deeper layers of the oceans are also included. Therefore, the increase in heat content is comparatively less influenced by surface climate phenomena and is considered a more important indicator of planetary warming.
"The ocean absorbs more than 90 per cent of the excess heat trapped by greenhouse gases, making it the main heat reservoir of the climate system. Because ocean heat content (OHC) reflects the accumulation of heat stored in the ocean, it provides one of the best indicators of long-term climate change," the study authors wrote. -- dpa
