Why nuclear war, not the climate crisis, is humanity’s biggest threat, according to one author

A still from an image broadcast on North Korean TV showing what it said was the launch of a ballistic missile in 2023. Photograph: AP

Climate breakdown is usually held up as the biggest, most urgent threat humans pose to the future of the planet today.

But what if there was another, greater, human-made threat that could snuff out not only human civilisation, but practically the entire biosphere, in the blink of an eye?