The World Meteorological Organisation (WMO) has announced that the La Niña phase of the El Niño Southern Oscillation (ENSO) phenomenon is likely to return to the Equatorial Pacific Ocean in September 2025. While La Niña typically has a cooling effect on global temperatures, the WMO predicts that overall temperatures will remain above normal due to the overriding influence of human-induced climate change.
What is La Niña?
La Niña is a climate pattern characterized by cooler-than-average sea surface temperatures in the Equatorial Pacific Ocean. This cooling alters global atmospheric circulation, impacting wind, pressure, and rainfall patterns in various regions around the world. The WMO states there is a 55% chance of La Niña conditions developing between September and November, with the probability increasing to 60% for the October to December period.
Climate Change Overrides Natural Cooling
Historically, La Niña events have provided a temporary cooling effect on global average temperatures. However, in the current era of human-induced climate change, this natural cooling is no longer enough to counteract the significant long-term warming trend. The WMO highlights that even during La Niña years, global temperatures have remained elevated, with 2022 a La Niña year being the fifth or sixth warmest on record. This demonstrates that naturally occurring climate events are now happening “in the broader context of human-induced climate change,” which is exacerbating extreme weather and impacting seasonal patterns.
Global Forecast and Economic Implications
The WMO’s forecast for September to November 2025 predicts above-normal temperatures for most of the Northern and Southern Hemispheres. Rainfall patterns are expected to resemble those typically seen during a moderate La Niña event. The WMO’s Secretary-General, Celeste Saulo, stressed the economic importance of these seasonal forecasts, noting that they provide millions of dollars in economic savings for sectors like agriculture, energy, and transport and can save thousands of lives by guiding preparedness and response actions.