“When you’re among young people, it’s hard for them to understand how long we’ve known all the basic facts about climate change,” said Rahmstorf, a scientist at the Potsdam Institute for Climate Impact Research who has worked on the topic for 35 years. “Even when I started as a PhD student in the 1980s, it was very clear that our emissions were causing global warming and all the consequences it would have.”

Yet even as Europe’s leaders acknowledge the scale and cause of the problem, they have weakened the very rules in place to stop it from getting worse. Two weeks ago, the European Commission proposed watering down the continent’s emissions trading system, a form of carbon market widely hailed as its most successful tool to cut pollution.

“What people are not getting is that we can’t turn this back – the CO2 to a large part remains in the air for thousands of years,” said Rahmstorf. “Some people think we can wait and, when it gets too bad, then we reduce emissions and things will get better again. People don’t realise that we can’t make it get better again. We can only prevent it from getting much worse.”

A study Rahmstorf co-authored in 2023 found ExxonMobil’s predictions of global heating over the following decades to have been mostly accurate, as skilful as independent academic and government models, and also very much at odds with its public statements on the matter.