The money is on the other side. A peer-reviewed study found that if the world acts to stabilise the climate, the world’s fossil fuel reserves – owned by oil companies and oil-producing states – would lose $13–17 trillion in value over the next two decades. A trillion is hard to imagine: if you earned $50,000 a year, earning $13 trillion would take you 260 million years – you’d have had to start before the dinosaurs. The study’s author concludes this gives fossil fuel producers “a strong incentive” to keep resisting climate action.

If it could be disproved, someone would have done it. Imagine a scientist who could genuinely prove that human-caused climate change wasn’t real. They’d win a Nobel Prize, and fossil fuel companies, with trillions at stake, would pay almost anything for the research. Yet decades on, no-one has managed it. Instead, the challenges tend to appear on social media, in anonymous reports and in think-tank pamphlets, rather than in peer-reviewed science journals, where evidence is checked by other experts. That tells you something.

They knew. A study in Science found that Exxon’s own scientists accurately projected global warming from the 1970s, while the company publicly cast doubt on climate science for decades.

The scientists aren’t paid by the IPCC. The thousands of experts who write the IPCC’s assessments volunteer their time. They aren’t paid by the IPCC, and their reports are reviewed line by line by other scientists and by governments.

A conspiracy would have to be impossibly large. Thousands of scientists in almost every country, across rival governments and competing institutions, would all have to keep the same secret for decades. Science rewards people who overturn ideas. Anyone who could genuinely disprove human-caused warming would be famous.

Who funds the doubt? Many of the voices claiming climate change is exaggerated are linked to lobby groups that don’t disclose their funders, or that have taken money from fossil fuel interests.