The recent onset of La Niña, a cooling phase in the equatorial Pacific, is anticipated to lower global temperatures. However, December 2024 recorded the second warmest December in history, with temperatures exceeding pre-industrial averages by over 1.5°C.
La Niña is identified when sea surface temperatures (SST) in the Niño 3.4 region drop by at least 0.5°C. Despite its arrival, five out of six global datasets indicated that December was significantly warmer than historical averages. Daily data from the Copernicus Climate Change Service shows that January 2025 continued this trend, with temperatures at least 1.64°C above pre-industrial levels.
Experts indicate a lag of approximately three months between La Niña's onset and its potential impact on global temperatures. While some cooling is expected, it is unlikely to be substantial, as current conditions are warmer than previous La Niña events. This suggests that the effects of La Niña are minimal compared to the long-term warming driven by greenhouse gas emissions, with forecasts indicating that 2025 could be among the hottest years recorded.