Climate change has intensified exceptional El Niño events like the 2026/27 forecast

Aditya Sengupta, Mandy Barbara Freund , Andrew King

Extreme El Niño events disrupt weather across much of the globe, with adverse effects on agriculture, fisheries and economic output that persist for several years. Event attribution routinely quantifies the human influence on individual heatwaves, droughts and floods, but its application to the El Niño events that drive many of them has been much more limited. Here we investigate the 2026/27 El Niño event, forecast to peak later this year. We assess it using the relative Niño3.4 index, adopted operationally by forecasting agencies, which measures the Niño3.4 anomaly against the concurrent tropical mean. Multimodel forecasts indicate a peak of 3.16°C, exceeding the largest event in the instrumental record (1982/83) in 84% of ensemble members. Using generalised Pareto fits to pre-industrial and current climate simulations from models evaluated on ENSO asymmetry, we find that an event of this magnitude is approximately six times more likely in the current climate. The 2026/27 forecast exemplifies how climate change is already altering the rarity and intensity of extreme El Niño events.