When the Paris agreement on climate change was gavelled into being in December 2015, it briefly looked like that rarest of things: a political victory for climate activists and delegates from the poorest regions of the world that, due to colonisation by today’s wealthy nations, have contributed little to the climate crisis – but stand to suffer its worst ravages.

The world had finally agreed an upper limit for global warming. And in a move that stunned most experts, it had embraced the stretch target of 1.5°C, the boundary that small island states, acutely threatened by sea-level rise, had tirelessly pushed for years.

Or so, at least, it seemed. For soon, the ambitious Paris agreement limit turned out to be not much of a limit at all…

De facto, what they said was this: staying below a temperature limit is the same as first crossing it and then, a few decades hence, using methods of removing carbon from the atmosphere to dial temperatures back down again.

From some corners of the scientific literature came the assertion that this was nothing more than fantasy. A new study published in Nature has now confirmed this critique.