‘Profound impacts’: record ocean heat is intensifying climate disasters, data shows

Oceans absorb 90% of global heating, making them a stark indicator of the relentless march of the climate crisis

The world’s oceans absorbed colossal amounts of heat in 2025, setting yet another new record and fuelling more extreme weather, scientists have reported.

More than 90% of the heat trapped by humanity’s carbon pollution is taken up by the oceans. This makes ocean heat one of the starkest indicators of the relentless march of the climate crisis, which will only end when emissions fall to zero. Almost every year since the start of the millennium has set a new ocean heat record.

This extra heat makes the hurricanes and typhoons hitting coastal communities more intense, causes heavier downpours of rain and greater flooding, and results in longer marine heatwaves, which decimate life in the seas. The rising heat is also a major driver of sea level rise via the thermal expansion of seawater, threatening billions of people.

Reliable ocean temperature measurements stretch back to the mid-20th century, but it is likely the oceans are at their hottest for at least 1,000 years and heating faster than at any time in the past 2,000 years.

The atmosphere is a smaller store of heat and more affected by natural climate variations such as the El Niño-La Niña cycle. The average surface air temperature in 2025 is expected to approximately tie with 2023 as the second-hottest year since records began in 1850, with 2024 being the hottest. Last year the planet moved into the cooler La Niña phase of the Pacific Ocean cycle.

“Each year the planet is warming – setting a new record has become a broken record,” said Prof John Abraham at the University of St Thomas in Minnesota, US, and part of the team that produced the new data.

“Global warming is ocean warming,” he said. “If you want to know how much the Earth has warmed or how fast we will warm into the future, the answer is in the oceans.”

The analysis, published in the journal Advances in Atmospheric Sciences, used temperature data collected by a range of instruments across the oceans and collated by three independent teams. They used this data to determine the heat content of the top 2,000 metres of the oceans, where most of the heat is absorbed.

The amount of heat taken up by the ocean is colossal, equivalent to more than 200 times the total amount of electricity used by humans across the world. “Ocean warming continues to exert profound impacts on the Earth system,” the scientists concluded.

Ocean warming is not uniform, with some areas warming faster than others. In 2025, the hottest areas included the tropical and South Atlantic and North Pacific oceans, and the Southern Ocean. In the latter, which surrounds Antarctica, scientists are deeply concerned about a collapse in winter sea ice in recent years.

Cover photo:  The extra heat makes hurricanes and typhoons more intense, causes heavier downpours of rain and greater flooding, and results in longer marine heatwaves. Photograph: Michael Probst/AP