2026 Has a 67% Chance of Becoming the Warmest Year on Record

With three-quarters of the year complete, 2026 is virtually certain to finish as either the warmest or second-warmest year in records, according to Carbon Brief’s analysis of six global temperature datasets. The analysis puts the chance of 2026 surpassing 2024 at 67% and projects an annual average of about 1.52C above pre-industrial levels.

The first nine months of 2026 were the second warmest on record, behind only the same period in 2024, at around 1.45C above pre-industrial levels. August was the warmest August in all six datasets, exceeding the previous record by about 0.12C on average. September ranked second, behind September 2023.

A rapidly strengthening El Niño has contributed to the recent heat alongside human-caused global warming. El Niño is the warm phase of a recurring tropical Pacific climate pattern that transfers heat from the ocean into the atmosphere. In September, sea-surface temperatures in the Niño3.4 region broke the previous daily record, set in 2015, and remained above it thereafter.

Forecasts assessed by Carbon Brief indicate that the event could peak at around 4C above average this winter. Because global temperatures typically respond to tropical Pacific conditions with a lag of about three months, the El Niño is expected to have its largest effect on global temperatures in 2027.

The likelihood of a 2026 record varies substantially by dataset. Carbon Brief estimates a 97% chance in Berkeley Earth and 82% in NASA’s GISTEMP, compared with 34% in NOAA’s dataset and 18% in the ERA5 reanalysis. The estimates are closer to an even chance in JRA-3Q and HadCRUT5. The differences reflect how datasets handle areas with fewer observations and, in some cases, use different methods to calculate temperatures.

Heat records were widespread during July-September. Around 22% of the world’s surface experienced its warmest such period in the ERA5 record, including much of the tropical Pacific, the western Mediterranean and Iberia. Western Europe had its hottest summer on record, while Spain recorded its warmest September, beating the previous record by 0.7C.

Carbon Brief projects that 2027 will average around 1.7C above pre-industrial levels, with a 96% chance of becoming the warmest year on record. That estimate is more uncertain because the year has not yet been observed and depends on how strong the El Niño becomes and how quickly it fades.

Sources: Carbon Brief.