Mysterious North Pacific Heatwave Shatters Temperature Records

In 2025, the north Pacific has seen its warmest summer on record, according to a BBC analysis of the region's mysterious marine heatwave. Sea surface temperatures between July and September were more than 0.25°C above the previous high, across an area roughly ten times the size of the Mediterranean.

While climate change is known to make marine heatwaves more likely, scientists are puzzled by the scale and duration of the current event. Some researchers believe the unusual warming in the so-called "warm blob" may have the opposite effect in the UK, potentially leading to a colder start to winter.

"There's definitely something unusual going on in the north Pacific," said Zeke Hausfather, a climate scientist at Berkeley Earth. The jump in temperatures across such a large region is "quite remarkable," he added.

Experts are exploring various factors that could be contributing to the exceptional conditions, including changes to shipping fuels and efforts to reduce air pollution in China. The heatwave has already had consequences for weather on both sides of the Pacific, and its impact on the UK and Europe in the coming months remains to be seen.