The average global temperature for October was 0.4°C above the previous record for the month, set in 2019, 0.85°C warmer than the 1991 to 2020 average and 1.7°C warmer than an estimate of pre-industrial levels between 1850 and 1900, analysis by the European Union-funded Copernicus Climate Change Service showed. This year is so far 1.43°C warmer than the pre-industrial average.

Read More: Climate Change Blamed as Europe’s Cities See Autumn Heat Waves

“The difference between the temperature of this October and the average temperature of October in the last 30 years is extraordinarily large, much larger than the anomaly of any of the other years that were record-breaking,” said Carlo Buontempo, director of the Copernicus Climate Change Service, in an interview with Bloomberg Green. “We are already in uncharted territory. We are already experiencing a climate that we have never seen in our life or in our history.”

Both November and December would need to be significantly colder than average in order for 2023 to avoid becoming the hottest year ever, Buontempo added, something the agency is not expecting. “It would need to be something incredibly large, like a major volcanic eruption, to really upset that. I think it’s fair to say that pending something close to apocalyptic we don’t expect 2023 not to be the warmest on record.”

The agency said in a statement the record is “virtually certain”.

The record-breaking global autumn temperatures follow the hottest summer on record for the world. Climate-change-driven heat affected most of the world’s population in some form, the nonprofit Climate Central found in September. It’s not surprising to see a warmer-than-average year — global temperatures are around 1.2°C above pre-industrial levels — but the temperature increase this summer and autumn “obliterated” previous records, said Samantha Burgess, deputy director of the Copernicus Climate Change Service, in a press release.

The heat is largely driven by greenhouse gasses released by burning fossil fuels, but the natural climate phenomenon El Niño is also driving temperatures higher, exacerbating already high sea-surface temperatures.

Read More: What Is El Niño and How Does it Affect Weather Around the World?

Climbing temperatures bring greater risks to human health from overheating, as well as increasing the severity of disasters including flooding, storms and wildfires. They also cause damage to nature including coral reefs and forests.   

The US National Oceanic and Atmospheric Administration said in October that there was a greater than 99.5% chance that 2023 would be the warmest year ever recorded — with two months of the year still to go.

On 23 October climate scientist Zeke Hausfather, a researcher with Berkeley Earth, said it was already clear that October would be the hottest on record “by a large margin”. 

“October 2023 will continue a string of months far warmer than anything that has come before in the instrumental record,” he said on the social media platforms Bluesky and X. September broke records set in 2020 by 0.5°C and was also around 1.7°C warmer than pre-industrial levels, a margin Hausfather called “gobsmackingly bananas”. 

The UK’s Met Office said parts of England’s southeast had seen maximum temperatures more than 4°C above the 1991-2020 average in October. Temperatures for the whole country had been “well above average,” a spokesperson said via email. Almost half of the Czech Republic’s 160 weather stations broke October temperature records mid-month, the country’s weather service said in a Facebook post, some of them by over 3°C.

Minneapolis hit 33.33° on 1 October, the hottest temperature recorded in the city in October, part of a heat wave that broke records across the eastern US and Midwest. A drought in Brazil led to record numbers of forest fires in the state of Amazonas and the river level at the Port of Manaus dropped to the lowest in 121 years.