Do rising methane levels herald a climate feedback loop?

The end of an ice age is a fearsome and complex thing. Ice sheets collapse; ocean currents shift; weather patterns are thrown awry; low-lying land is inundated. Each change triggers more change, mostly in a way that makes the world warmer still.

Such “terminations” are visible in the geological record. When ice ages end, says Euan Nisbet of Royal Holloway, University of London, a sudden rise in airborne methane levels “is the bellwether, right at the beginning of [the] changes. The melting of the ice takes thousands of years. But the atmospheric change can be…a matter of decades.” And when Dr Nisbet looks at today’s atmospheric data, he sees something that looks worryingly termination-like.