A rapidly intensifying El Niño in the tropical Pacific has nearly doubled the odds that 2026 becomes the warmest year on record, with forecast models now projecting the strongest event in modern observational history.
Carbon Brief’s climate analysis puts the chance of 2026 beating 2024’s global temperature record at 35%, up from 19% just four months ago. The shift is driven almost entirely by escalating El Niño forecasts, with sea surface temperatures in the key Niño3.4 region climbing from 0.5C in April to 1.6C by June — one of the fastest onsets ever observed.
El Niño 2026 On Track to Break Records
El Niño, the warm phase of the El Niño-Southern Oscillation (ENSO), releases stored ocean heat into the atmosphere and temporarily raises global temperatures while reshaping rainfall and extreme weather patterns worldwide. After two years dominated by the cool La Niña phase, the tropical Pacific flipped decisively in April 2026.
By early July, the Niño3.4 index had already exceeded 2C, outpacing every prior El Niño development speed in the observational record. An analysis of 667 model runs from 14 modelling groups — including CFS, NMME, C3S, CanSIPS and SINTEX-F — projects a median peak of 3.59C between July and December. More than 91% of runs predict a peak stronger than the 2015-16 event, which previously held the record at roughly 2.75C.
Adjusting for Ocean Warming
Raw Niño3.4 measurements use a fixed climatology, which can overstate event strength because the entire tropical ocean has warmed due to human-caused greenhouse gas emissions. A cleaner metric, the relative Niño3.4 index (RONI), subtracts average tropical warming to enable fairer historical comparison.
Even under RONI, the median forecast peak reaches 3.1C, well above the prior relative record of 2.69C set in 1982-83. Some 77% of model runs still show a new record event occurring. On both measures, the central expectation is for the strongest El Niño in the observational record.
Forecasters urge some caution. Spring and early-summer model runs have historically overpredicted El Niño strength, though forecasts issued after spring tend to be considerably more reliable.
Global Temperature Implications
The first six months of 2026 ranked as the third-warmest start to any year across all six major surface temperature datasets — NASA GISTEMP, NOAA GlobalTemp, HadCRUT5, Berkeley Earth, ERA5 and JRA-3Q — at roughly 1.4C above pre-industrial levels. Only 2024 and 2025 were warmer.
January began as the fourth or fifth warmest on record, suppressed by lingering weak La Niña conditions. Each subsequent month climbed the rankings. May and June both came in as the second-warmest ever recorded. Copernicus also reported that global sea surface temperatures over ice-free oceans set a new June record.
Carbon Brief’s central estimate remains that 2026 will finish as the second-warmest year, at around 1.51C above pre-industrial levels. Record odds vary sharply by dataset: roughly two-in-three in NASA and Berkeley Earth data, around two-in-10 in ERA5, and one-in-10 in JRA-3Q reanalyses.
Regional Extremes and Arctic Sea Ice
June 2026 was western Europe’s hottest June on record, with a heatwave that broke hundreds of individual station records. Nearly 9% of the planet’s surface experienced record June warmth.
Arctic sea ice has spent 39 days of 2026 so far at or below record daily lows, following a joint-lowest winter maximum in the satellite era. The combination of El Niño-driven atmospheric warmth and long-term polar amplification continues to erode cryospheric stability.
What Happens Next
The developing El Niño will have its largest impact on 2027, which Carbon Brief projects at around 1.7C above pre-industrial levels — comfortably a new annual record. Policymakers and climate adaptation planners should prepare for intensified drought in the southern US, heavier rainfall across Australia and equatorial South America, and elevated global temperature anomalies through at least mid-2027.
Watch for the Niño3.4 peak timing in November or December, when most models converge, and for whether RONI-adjusted forecasts hold above the 1982-83 benchmark. The gap between raw and relative indexes will also signal how much of the event’s apparent strength reflects underlying ocean warming versus genuine ENSO variability.
— Rachel Greenwood, climate desk, AXO News