October 2026 was the warmest October ever recorded on Earth, the European Union’s Copernicus Climate Change Service said on Friday — and the year is now almost certain to pass 1.5 degrees Celsius above pre-industrial levels, only the second calendar year ever to do so.
Last month’s average global surface temperature was 15.35 degrees Celsius, Copernicus said, 0.90 degrees above the 1991–2020 average for October and 1.75 degrees above the estimated 1850–1900 pre-industrial level. It was the third month in a row above the 1.5-degree mark, after August and September. The previous October record, set in 2023, was beaten by 0.05 degrees.
The numbers behind the headline are stark. Copernicus puts the probability that 2026 as a whole exceeds 1.5 degrees at more than 99 percent — what the service calls “virtually certain” — with a predicted range of 1.56 to 1.61 degrees. The service said 2026 is most likely to be the second-warmest year on record, with about an 80 percent chance of that ranking and a 20 percent chance of tying or exceeding 2024, currently the warmest year ever recorded. The four-year average for 2023 to 2026 is also expected to pass 1.5 degrees.
The oceans did much of the work. The average sea surface temperature outside the polar regions reached 20.95 degrees in October, the highest on record for the month, beating the previous October record set in 2023. El Niño conditions intensifying in the tropical Pacific are still strengthening, and Copernicus said the extra-polar oceans drove the global record: land temperatures, by contrast, were only joint third-warmest for October. Europe had its second-warmest October on record, after the hottest summer ever recorded in Western Europe.
There is an important distinction in what the 1.5-degree figure means, and it is one that gets lost in most headlines. Under the 2015 Paris Agreement, countries agreed to try to limit long-term global warming to 1.5 degrees above pre-industrial levels — but the target refers to a long-term average, so a single year above the mark does not mean it has formally been breached. “2026 is on track to become the second calendar year above 1.5°C,” Samantha Burgess of the European Centre for Medium-Range Weather Forecasts, which runs Copernicus, said in the service’s announcement. A year over the line is a warning. It is not the line being crossed.
That warning is getting harder to ignore. The last twelve months, November 2025 to October 2026, averaged 1.51 degrees above pre-industrial levels. Two of the last three calendar years will have finished above 1.5 degrees. The Paris target was designed as a guardrail measured over decades; the climate is now spending whole years on the wrong side of it, and the four-year average is about to join them.
What happens next depends less on the thermometers than on the politics. The figures land as governments prepare their next round of climate pledges, and they will be read in two opposite ways: as proof that the 1.5-degree goal is slipping away, and as proof that it still matters enough to fight for. Copernicus will publish its full-year assessment in January. On current data, it already knows what it will say.
