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The planet is hurtling towards an El Niño during the northern hemisphere summer of 2026. Forecasts suggest it could rival the episode of 1876-78, the strongest on record, which triggered droughts and famines across large parts of the world and contributed to the deaths of 50 million people.
On June 2, the World Meteorological Organisation (WMO) said there was an 80 per cent chance of El Niño conditions developing in the equatorial Pacific between June and August, rising to a 90 per cent chance that it would persist until at least November. A day earlier, the US National Oceanic and Atmospheric Administration (NOAA) put the odds of El Niño emerging between May and July at 82 per cent, and estimated a 96 per cent chance that it would continue through the northern hemisphere winter of 2026-27.
El Niño is typically associated with higher global temperatures, below-average rainfall across many regions, excessive rainfall in others and an increased likelihood of extreme weather. However, no two El Niño events are identical. Their effects depend on the pattern of ocean warming in the tropical Pacific, the state of the atmosphere and natural climate variability.
The crucial difference between a potential 2026 El Niño and those of the past, particularly the one in 1876-78, is the backdrop against which it will unfold. Human-driven climate change has warmed both the oceans and the atmosphere.
According to the EU’s Copernicus Climate Change Service, the planet is now about 1.4°C warmer than it was during the pre-industrial period of 1850-1900. This can amplify the effects of El Niño.
“The El Niño event now likely to develop by late summer has a high chance of becoming strong to very strong, even when accounting for the ‘rising tide’ effect, whereby warming oceans raise the baseline tempe- rature of the sea surface,” said Daniel Swain, a climate scientist at the California Institute for Water Resources at the University of California Agriculture and Natural Resources, US, at a press briefing.
The strength of an El Niño event is measured using the Oceanic Niño Index (ONI), which tracks average sea-surface temperature anomalies in a region of the equatorial Pacific known as Niño 3.4. An El Niño is declared when the ONI exceeds 0.5°C. Values between 0.5°C and 1°C are classified as weak; those between 1°C and 1.5°C as moderate.
An ONI above 1.5°C denotes a strong event, while one above 2°C is considered very strong. Events that rise well beyond 2°C, such as those of 1982-83, 1997-98 and 2015-16, are often referred to as “super El Niño”. This means either 2026 or 2027, or both...
This article was originally published in the June 16-30, 2026 print edition of Down To Earth