Summary
Sea-surface temperatures in the central tropical Pacific were about 2.9°C above the current climate baseline in early September, and forecasts give the event more than a 90% chance of surpassing every El Niño recorded since the 1870s. The expected effects vary by region but include drought, crop losses, peatland fires, floods and coral bleaching.
An El Niño event now developing in the tropical Pacific could become the strongest in recorded observations, according to a Nature World View by climate scientist Zeke Hausfather. In early September, sea-surface temperatures in the central tropical Pacific were about 2.9°C above the current climate baseline—the average temperature for the previous 30 years.
Hausfather says he monitors observations and forecasts from 14 leading models. Those forecasts give the event more than a 90% chance of surpassing every El Niño recorded since observations began in the 1870s. The comparison is especially striking because temperatures were already more than 1°C higher than at the same stage of the powerful 1997 and 2015 events.
Why the Pacific warming matters
El Niño is a recurring climate pattern in which unusually warm tropical Pacific waters alter atmospheric circulation and redistribute rainfall. Its effects are not uniform: some regions tend to become substantially drier while others face heavier rainfall and flooding.
The current event is therefore important not only because of the temperature measured in the Pacific, but also because of the risks that follow across food systems, forests, public health and coastal ecosystems. The source identifies drought and failed harvests, floods, wildfires in dry forests and peatlands, and coral bleaching among the main hazards. It says agencies from national agriculture ministries to the World Health Organization should begin preparations immediately.
Southern Africa is one of the clearest drought-risk regions. During the four strongest El Niño events between 1980 and 2016, the region had roughly an 80% chance of below-normal rainfall during the December–February wet season. The comparatively moderate 2023–24 El Niño still produced severe drought, disaster declarations in Zimbabwe, Zambia and Malawi, and the lowest recorded flow of the Zambezi River.
The agricultural consequences can be substantial. South Africa’s maize harvest fell by nearly half during the 2015–16 El Niño. Because the planting season begins in October, Hausfather says governments in high-risk areas have only a short window to distribute drought-tolerant and early-maturing crop varieties and expand programmes that support households when harvests fail.
Indonesia faces fire and health risks
Rainfall is already declining across Indonesia, increasing the risk of peatland fires. These fires can release large quantities of carbon dioxide and produce smoke that affects several countries.
During the 1997 El Niño, Indonesian fires emitted an estimated 3–9 gigatonnes of carbon dioxide—equivalent to roughly 13–40% of global fossil-fuel emissions that year. Fires and haze during the 2015 event were linked to around 100,000 excess deaths across Indonesia, Malaysia and Singapore.
Indonesia has established a peatland-restoration agency and restricted the clearing of primary forests and peatlands. The source argues that these measures make early prevention and preparedness particularly important as rainfall declines.
The assessment is a forward-looking expert analysis based on current observations and model forecasts. The more-than-90% figure describes the projected likelihood of the event exceeding historical El Niño levels; its final intensity and regional effects will depend on how the event develops. Regional outcomes will also differ, with drought in some areas occurring alongside flooding or other hazards elsewhere.