The past 12 months were the hottest ever on record

The 12 months between November 2022 and October 2023 saw global average temperatures rise 1.32°C above the preindustrial average – that is 0.03°C above the previous record set between October 2015 and September 2016.

“This is the hottest temperature our planet has experienced in something like 125,000 years,” says Andrew Pershing at Climate Central, a climate science nonprofit in the US.

Pershing and his colleagues based their analysis on surface temperature data from the European Centre for Medium-Range Weather Forecasts. They found that the main driver of the heat was global warming due to rising concentrations of greenhouse gases in the atmosphere.

Attributing the exact amount of warming to different factors is challenging, but Friederike Otto at Imperial College London says about 1.28°C of the rise in average temperatures can be attributed to climate change.

The team found much of the rest of the heat could be attributed to the shift to a warm El Niño climate pattern in the Pacific Ocean in June. “There’s only a very small part of this 1.32°C that is natural variability,” says Otto.

The researchers also used climate models to compare the likelihood of the extreme heat seen in countries around the world with and without the influence of human-caused climate change. During the period they studied, around 90 per cent of the world’s population was exposed to at least 10 days with heat made substantially more likely by climate change. Nearly 2 billion people saw at least a five-day streak of extreme temperatures made at least twice as likely by climate change.

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“It’s really affecting every human on this planet. And it’s mostly affecting the most vulnerable people,” says Joyce Kimutai at the Kenya Meteorological Department. 

This adds to a slew of studies this past year attributing extreme weather events seen across the world in part to climate change, from the record-breaking wildfires in Canada to drought in East Africa. With the developing El Niño not expected to reach peak strength until the next few months, however, Pershing says the coming 12 months are likely to be even hotter – possibly rising more than 1.4°C above the preindustrial baseline. Previous forecasts have suggested that 2024 could see global average temperatures rise above even 1.5°C.