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 big increase across 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.
Yet this extra heat in the 'warm blob' may paradoxically make a colder start to winter in the UK more likely, some researchers believe.
There's definitely something unusual going on in the north Pacific, said Zeke Hausfather, a climate scientist at Berkeley Earth, a research group in the US. Such a jump in temperatures across a region so large is quite remarkable, he added. The BBC analysed data from the European Copernicus climate service to calculate average temperatures between July and September across a large area of the north Pacific, sometimes known as the 'warm blob'. The figures show that 2025 marks a significant increase compared to previous years.
Natural variability likely contributes to these changes, with this summer seeing weaker-than-usual winds, allowing more heat from the sun to remain at the surface. But additional factors are at play, including changes in shipping fuel regulations that have reduced harmful emissions but also decreased the natural cooling effects of sulphur in the atmosphere.
This extraordinary heat could have global repercussions, including a potential impact on weather patterns in Europe. The north Pacific's marine heatwave has already influenced extreme weather, resulting in intense heat in Japan and supercharged storms in California.
Long-term weather forecasting remains complex; however, the effects of this marine heat and the underlying influences of phenomena like La Niña, currently seen in the southern Pacific, will play vital roles in shaping winter weather conditions worldwide. As scientists continue to study these remarkable changes, the implications for our climate ecosystem and future weather remain profound.
Yet this extra heat in the 'warm blob' may paradoxically make a colder start to winter in the UK more likely, some researchers believe.
There's definitely something unusual going on in the north Pacific, said Zeke Hausfather, a climate scientist at Berkeley Earth, a research group in the US. Such a jump in temperatures across a region so large is quite remarkable, he added. The BBC analysed data from the European Copernicus climate service to calculate average temperatures between July and September across a large area of the north Pacific, sometimes known as the 'warm blob'. The figures show that 2025 marks a significant increase compared to previous years.
Natural variability likely contributes to these changes, with this summer seeing weaker-than-usual winds, allowing more heat from the sun to remain at the surface. But additional factors are at play, including changes in shipping fuel regulations that have reduced harmful emissions but also decreased the natural cooling effects of sulphur in the atmosphere.
This extraordinary heat could have global repercussions, including a potential impact on weather patterns in Europe. The north Pacific's marine heatwave has already influenced extreme weather, resulting in intense heat in Japan and supercharged storms in California.
Long-term weather forecasting remains complex; however, the effects of this marine heat and the underlying influences of phenomena like La Niña, currently seen in the southern Pacific, will play vital roles in shaping winter weather conditions worldwide. As scientists continue to study these remarkable changes, the implications for our climate ecosystem and future weather remain profound.
