Nature, Published online: 26 March 2025; doi:10.1038/d41586-025-00888-5Global sea surface temperatures in 202324 exceeded the previous record by an unprecedented margin. Observation-based statistical models and climate models suggest that such jumps in ocean temperatures are unlikely to occur even with global warming but are almost impossible without it. In climate models, temperatures revert to the long-term warming trend in the years after such jumps.