The waters of the North Pacific have had their warmest summer on record, according to BBC analysis of a mysterious marine heatwave that has confounded climate scientists. Sea surface temperatures between July and September were more than 0.25C above the previous high of 2022 - a considerable increase over an area roughly ten times the size of the Mediterranean.
While climate change is known to make marine heatwaves more likely, scientists are struggling to explain why the North Pacific has been so hot for so long. The extra heat in the so-called 'warm blob' may even lead to a colder start to winter in the UK, some researchers believe.
There's definitely something unusual going on in the North Pacific, noted Zeke Hausfather, a climate scientist at Berkeley Earth. The extraordinary jump in temperatures across such a large area is quite remarkable, he affirmed.
Recent data analysis from the European Copernicus climate service has shown that the North Pacific region, extending from Asia to North America, has been warming significantly over the past two decades, with 2025 showing even higher temperatures than in recent years.
The waters are not just warming due to climate change; events like lower-than-normal winds have kept the summer heat trapped in the ocean's surface. Therefore, while natural variability plays a role, climate experts suspect that human activity—particularly changes in shipping regulations that have reduced sulphur emissions—might be revealing the full impact of global warming.
Beyond the North Pacific, the heatwave has also affected weather patterns in Japan, South Korea, and the United States, leading to extreme summer temperatures and intensified storms. Long-term forecasts suggest that this could also influence UK and European weather this winter, possibly resulting in colder conditions early on.
Adding complexity to the situation is the weakening La Niña phenomenon in the tropical Pacific, typically associated with a higher risk of cooler weather in the UK. This winter could witness an interplay between the warm conditions in the North Pacific and the cool conditions typical of La Niña, altering our weather patterns in unprecedented ways.
While climate change is known to make marine heatwaves more likely, scientists are struggling to explain why the North Pacific has been so hot for so long. The extra heat in the so-called 'warm blob' may even lead to a colder start to winter in the UK, some researchers believe.
There's definitely something unusual going on in the North Pacific, noted Zeke Hausfather, a climate scientist at Berkeley Earth. The extraordinary jump in temperatures across such a large area is quite remarkable, he affirmed.
Recent data analysis from the European Copernicus climate service has shown that the North Pacific region, extending from Asia to North America, has been warming significantly over the past two decades, with 2025 showing even higher temperatures than in recent years.
The waters are not just warming due to climate change; events like lower-than-normal winds have kept the summer heat trapped in the ocean's surface. Therefore, while natural variability plays a role, climate experts suspect that human activity—particularly changes in shipping regulations that have reduced sulphur emissions—might be revealing the full impact of global warming.
Beyond the North Pacific, the heatwave has also affected weather patterns in Japan, South Korea, and the United States, leading to extreme summer temperatures and intensified storms. Long-term forecasts suggest that this could also influence UK and European weather this winter, possibly resulting in colder conditions early on.
Adding complexity to the situation is the weakening La Niña phenomenon in the tropical Pacific, typically associated with a higher risk of cooler weather in the UK. This winter could witness an interplay between the warm conditions in the North Pacific and the cool conditions typical of La Niña, altering our weather patterns in unprecedented ways.
