Last month was the warmest October ever recorded, the third consecutive month to run more than 1.5C above the pre-industrial average, according to the European Union's Copernicus Climate Change Service.
The numbers
The global average surface air temperature for October was 15.35C. That is 0.90C above the 1991-2020 average for the month and 1.75C above the estimated pre-industrial level, and it edges past the previous October record set in 2023.
Based on data through October, Copernicus expects the 2026 annual average to fall between 1.56C and 1.61C above pre-industrial levels. The service puts an 80% chance on 2026 finishing as the second-warmest year on record and a 20% chance that it equals or passes 2024.
The ocean set its own record
Sea surface temperatures outside the polar regions averaged 20.95C, the highest October value on record and the fourth straight month to set a monthly record. Warmth was widespread rather than confined to one basin, with much-above-average water temperatures in the North Atlantic, the Mediterranean and parts of the Indian Ocean.
For Europe as a whole, October was the second-warmest on record. Parts of southern and eastern Europe stayed warm into November, extending a growing season that has already been disrupted by autumn heat in three of the past five years.
El Nino is still strengthening
The tropical Pacific is in an exceptionally strong El Nino, and the Nino 3.4 region recorded an anomaly of 3.21C. El Nino years tend to lift the global average with a lag, which is one reason forecasters expect the first half of 2027 to stay hot even if the pattern weakens.
The immediate effects are practical. Warm ocean water feeds stronger tropical storms, and a warm Pacific shifts rainfall away from Indonesia and eastern Australia while adding moisture to the eastern Pacific coast of the Americas.
The numbers leaders will carry to Antalya
The bulletin lands two days before COP31 opens in Antalya, Türkiye, where negotiators will spend two weeks on finance, adaptation and the next round of national pledges. Delegations that arrived planning to talk about 2035 targets will now be asked why the last twelve months ran above the threshold the Paris Agreement was designed to hold.