Late last week, global temperatures briefly passed a benchmark that climate scientists have been dreading. Provisional data suggests the mean global temperature likely crossed a critical threshold of 2°C (3.6°F) above pre-industrial levels last Friday for the first time in recorded history.

“Provisional ERA5 global temperature for 17th November from @CopernicusECMWF was 1.17°C above 1991-2020 – the warmest on record,” Dr Sam Burgess, the deputy director of the Copernicus Climate Change Service, posted on X (formerly Twitter) on Sunday.

"Our best estimate is that this was the first day when global temperature was more than 2°C above 1850-1900 (or pre-industrial) levels, at 2.06°C," she said.

Dr Burgess added that provisional data for Saturday, November 18 showed the global average temperatures were 2.06°C above preindustrial levels.

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There’s a lot of evidence that if Earth stays consistently over 2°C (3.6°F) above pre-industrial levels, it will dramatically impact the environment and its inhabitants (including us). 

In a “2°C world,” it is almost certainly game over for over 99 percent of the world’s coral reefs. We’re also likely to see significantly more declines in insects, 16 percent of plants, and 8 percent of vertebrates, compared to just 1.5°C (2.7°F) of warming. It could also lead several hundred million people into climate-related poverty. 

The 2°C threshold was a central tenet of the Paris Climate Agreement in 2015 when international leaders agreed to keep global warming “well below 2°C above pre-industrial levels” with the hopes to limit this to just 1.5°C. 

Once again, this is only provisional data and the global average temperature only broke the threshold for a day. To fully gauge the impact of climate change, we need to think in terms of years, decades, and long-term trends, not odd days here and there. That said, some are seeing these record figures as an important benchmark – and far from a one-off.

This year has repeatedly seen record-smashing temperatures. The world’s hottest day since records began was seen on July 3, 2023, but it was quickly beaten by temperatures on July 4, which was almost 1°C (1.8°F) higher than the 1979-2000 average.

These single days are riding part of a bigger trend. Scientists have forecasted that 2023 is likely to see the hottest global surface temperatures in recorded history. Moreover, there's a good chance we'll see record-smashing temperatures in 2024 too if current trajectories are anything to go by.

Climate scientists and activists often talk of “keeping 1.5°C alive,” expressing hope that the world can take enough action to stay well below the 2°C threshold. While this weekend’s high global temperatures don’t mean that dream is dead, it should provide a worrying wake-up call to where we might be heading.