Turns out that fossil fuels are dangerous even when we are not around to burn them:

FOSSIL fuels have a new crime to live down. A frenzy of hydrocarbon burning at the end of the Permian period may have led to the most devastating mass extinction Earth has ever seen, as explosive encounters between magma and coal released more carbon dioxide in the course of a few years than in all of human history.

Around 250 million years ago, the so-called “Great Dying” saw 70 per cent of species wiped out on land and 95 per cent in the oceans. A clue to what may have triggered this disaster lies in solidified magma from this time, which is widespread in an area of Siberia where coal is also abundant.

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“You’re basically going to have something like a fire fountain every few kilometres or so over this vast moonscape that’s erupting, with flares going high into the air and columns of smoke and fly ash,” says Sleep. The ground would be “covered with coal tar and coal fragments and pieces of basalt”, he adds.

Dust injected into the stratosphere would cause drastic cooling. That would quickly switch to warming as the dust settled out of the atmosphere, leaving nothing to counteract the greenhouse effect of the increased CO₂. The climate might have swung between heating and cooling as new eruptions injected yet more dust into the stratosphere. “The climate is just going to go completely unstable,” says Sleep, who presented the idea last month at a meeting of the Geological Society of America in Portland, Oregon. (New Scientist via Bruce Sterling’s Twitter)