January 2025 was the hottest on record – a whole 1.7°C above pre-industrial levels. If many climate-watchers expected the world to cool slightly this year thanks to the natural “La Niña” phenomenon, the climate itself didn’t seem to get the memo.
In fact, January 2025’s record heat highlights how human-driven ocean warming is increasingly overwhelming these natural climate patterns.
La Niña is a part of the El Niño southern oscillation, a climate fluctuation that slowly sloshes vast bodies of water and heat between different ocean basins and disrupts weather patterns around the world. El Niño was first identified and christened by Peruvian fishermen who noticed a dismal drop in their catch of sardines that coincided with much warmer than usual coastal waters.
El Niño is now well known to be part of a grander climate reorganisation that also has a reverse cool phase, La Niña. As vast swathes of the eastern Pacific cool down during La Niña, this has knock-on effects for atmospheric weather patterns, shifting the most vigorous storms from the central Pacific to the west and disrupting the prevailing winds across the globe.
This atmospheric reaction also helps to amplify the sea surface temperature changes. Typically, La Niña will lower the global temperature by a couple of tenths of a degree Celsius.
In 2024 the Pacific swung from moderate El Niño conditions to...
