How fossil fuel burning nearly wiped out life on Earth – 250m years ago #Auspol

New evidence shows that catastrophic climate change probably destroyed 96% of species at the end of the Permian period. It could happen again

In the media, if not scientific literature, global catastrophes have long been associated with asteroid strikes. But as the dating of rocks has improved, the links have vanished. Even the famous meteorite impact at Chicxulub in Mexico, widely blamed for the destruction of the dinosaurs, was out of sync by more than 100,000 years.

The story that emerges repeatedly from the fossil record is mass extinction caused by three deadly impacts, occurring simultaneously: global warming, the acidification of the oceans and the loss of oxygen from seawater. All these effects are caused by large amounts of carbon dioxide entering the atmosphere. When seawater absorbs CO2, its acidity increases. As temperatures rise, circulation in the oceans stalls, preventing oxygen from reaching the depths.
The great outgassings of the past were caused by volcanic activity that were orders of magnitude greater than the eruptions we sometimes witness today. The dinosaurs appear to have been wiped out by the formation of the Deccan Traps in India: an outpouring on such a scale that one river of lava flowed for 1,500km. But that event was dwarfed by a far greater one, 190m years earlier, that wiped out 96% of marine life as well as most of the species on land.

What was the cause? It now appears that it might have been the burning of fossil fuel. Before I explain this extraordinary contention, it’s worth taking a moment to consider what mass extinction means. This catastrophe, at the end of the Permian period about 252m years ago, wiped out not just species within the world’s ecosystems but the ecosystems themselves. Forests and coral reefs vanished from the fossil record for some 10 million years. 

The latest research into the catastrophe at the end of the Permian is summarised in two articles by the geologist John Mason on the Skeptical Science site. The strongest clues all seem to point to the same conclusion: that the extinctions were triggered by the eruption of an igneous belt even bigger than the Deccan plateau: the Siberian Traps. As well as CO2, the volcanoes there produced sulphur dioxide, chlorides and fluorides, causing acid rain and the depletion of ozone.

But because carbon dioxide’s residence time in the atmosphere is greater than that of these other gases, it’s likely to have been the major cause of extinction. The change of state – including a rise in oceanic temperatures of 6-10C – was too sudden and sustained to permit the majority of life forms to adapt. The onset of mass extinction coincides with a giant carbon spike “so distinctive that it serves as a marker-horizon all over the world”.

And today? According to a paper published in 2013, the current rate of ocean acidification, caused by the burning of fossil fuels, is faster than at any time in the past 300m years. During the Permian mass extinction, the eruption of the Siberian Traps through the Tunguska basin seems to have produced between one and two gigatonnes of carbon dioxide a year. Today fossil fuel burning produces 30 gigatonnes a year.

Isis? Global security? If anyone were to survive a mass extinction on the scale of the Permian catastrophe, they would look back and shake their heads, amazed that we could have considered such issues more important.

Press link for more: George Monbiot | theguardian.com