Two months above 1.5°C: what Copernicus says about the run into 2027

September 2026 was the second-warmest September on record, and the second consecutive month above 1.5°C. That run, the Copernicus Climate Change Service says, is likely to continue into 2027.

The service's data, released on 9 October 2026, put the global average surface air temperature for September at 16.27°C. That is 0.82°C above the 1991–2020 average for the month and 0.11°C cooler than September 2023, the warmest September on record. Against the estimated 1850–1900 pre-industrial baseline, September 2026 ran 1.63°C above average.

The 1.5°C figure in the Paris Agreement refers to a long-term average, not a single month. Two consecutive months above it is not a formal breach. But the run began in August, and before that the last month to exceed 1.5°C was November 2025. Carlo Buontempo, Director of C3S, said temperatures are likely to remain above 1.5°C into 2027 and that crossing the agreement's long-term limit is only a matter of time.

The physical engine behind the run is visible in the oceans. Extra-polar sea surface temperatures, measured between 60°S and 60°N, were the highest on record for September. An intensifying El Niño pushed a key Pacific monitoring region to 29.70°C in September, a record, and forecasters expect the pattern to become the strongest ever recorded this year.

Other September records fell in the same direction. Global land temperature was the second highest for the month at 13.67°C, behind 14.10°C in September 2023. Antarctic sea ice reached its third-lowest annual winter maximum. Europe had its third-warmest September, and western Europe its joint-warmest with 2023.

The consequences are already measurable on the ground. Prolonged dry conditions produced record-low river flows in parts of the Rhine, Danube, Vistula and Garonne-Dordogne — waterways that carry navigation, industry and water supply.