The Copernicus Climate Change Service (C3S), implemented by the European Centre for Medium-Range Weather Forecasts on behalf of the European Commission with funding from the EU, routinely publishes monthly climate bulletins reporting on the changes observed in global surface air and sea temperatures, sea ice cover and hydrological variables.

Data showed October 2023 was the warmest October on record globally, with an average surface air temperature of 15.30°C, 0.85°C above the 1991-2020 average for October and 0.40°C above the previous warmest October, in 2019. 

The global temperature anomaly for October 2023 was the second highest across all months in the ERA5 dataset, behind September 2023. 

The month as a whole was 1.7°C warmer than an estimate of the October average for 1850-1900, the designated pre-industrial reference period. 

For the calendar year to date, January to October, the global mean temperature for 2023 is the highest on record, 1.43°C above the 1850-1900 pre-industrial average, and 0.10°C higher than the ten-month average for 2016, currently the warmest calendar year on record.

For Europe, October 2023 was the fourth warmest October on record, 1.30°C higher than the 1991-2020 average. 

The average sea surface temperature for October over 60°S–60°N was 20.79°C, the highest on record for October. 

El Niño conditions continued to develop in the equatorial Pacific, although anomalies remain lower than those reached at this time of year during the development of the historically strong 1997 and 2015 events.

According to Samantha Burgess, Deputy Director of the Copernicus Climate Change Service (C3S): "October 2023 has seen exceptional temperature anomalies, following on from four months of global temperature records being obliterated. We can say with near certainty that 2023 will be the warmest year on record, and is currently 1.43ºC above the preindustrial average. The sense of urgency for ambitious climate action going into COP28 has never been higher.”