Permian-Triassic boundary in shallow marine sediments, characterised by a significant sedimentation gap between the black shales of Permian and dolomites of Triassic age. This gap documents a globally recognized regression phase, probably linked to a period of a cold climate and glaciation.
CREDIT
© H. Bucher, Zürich

Guest essay by Eric Worrall

A paper published in Paleoworld worries that a repeat of the greatest mass extinction event in Earth’s history could be triggered by Anthropogenic CO2. But Cambridge Professor Peter Wadhams, our favourite sea ice alarmist, thinks the attempt to link the Permian extinction to modern events is a bit wild.

Earth’s worst-ever mass extinction of life holds ‘apocalyptic’ warning about climate change, say scientists

Runaway global warming saw the planet’s average temperature hit about double what it is today about 250 million years ago

Ian Johnston Environment Correspondent @montaukian Friday 24 March 2017 13:15 GMT

Researchers studying the largest-ever mass extinction in Earth’s history claim to have found evidence that it was caused by runaway global warming – and that the “apocalyptic” events of 250 million years ago could happen again.

About 90 per cent of all the living things on the planet were wiped out in the Permian mass extinction – described in a 2005 book called When Life Nearly Died – for reasons that have been long debated by scientists.

…

Now a team of researchers from Canada, Italy, Germany and the US say they have discovered what happened and that their findings have “an important lesson for humanity” in how we deal with current global warming.

According to a paper published in the journal  Palaeoworld, volcanic eruptions pumped large amounts of carbon dioxide into the air, causing average temperatures to rise by eight to 11°C.

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Professor Peter Wadhams, head of the Polar Ocean Physics Group at Cambridge University, suggested a major methane pulse was possible.

However he said this would be “maybe not apocalyptic, but catastrophic”.

“If there were a large methane release, which is now possible because of the instability of the methane hydrates underneath the Arctic continental shelves, the off-shore waters, that could quite easily give rise to a very large pulse,” Professor Wadhams said.

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However, Professor Wadhams criticised the title of the Palaeoworld paper, which was “Methane hydrate: Killer cause of Earth’s greatest mass extinction”.

“There’s a serious tendency these days to offer a breathless overkill on the importance of a discovery. The title of the paper is over the top,” he said.

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Read more: http://ift.tt/2nLEeUL

The abstract of the paper;

Methane Hydrate: Killer cause of Earth’s greatest mass extinction

Uwe Branda Nigel Blameya, Claudio Garbellib, Erika Griesshaberc, Renato Posenatod, Lucia Angiolinib, Karem Azmye, Enzo Farabegolif, Rosemarie Cameg

The cause for the end Permian mass extinction, the greatest challenge life on Earth faced in its geologic history, is still hotly debated by scientists. The most significant marker of this event is the negative δ¹³C shift and rebound recorded in marine carbonates with a duration ranging from 2000 to 19 000 years depending on localities and sedimentation rates. Leading causes for the event are Siberian trap volcanism and the emission of greenhouse gases with consequent global warming. Measurements of gases vaulted in calcite of end Permian brachiopods and whole rock document significant differences in normal atmospheric equilibrium concentration in gases between modern and end Permian seawaters. The gas composition of the end Permian brachiopod-inclusions reflects dramatically higher seawater carbon dioxide and methane contents leading up to the biotic event. Initial global warming of 8–11 °C sourced by isotopically light carbon dioxide from volcanic emissions triggered the release of isotopically lighter methane from permafrost and shelf sediment methane hydrates. Consequently, the huge quantities of methane emitted into the atmosphere and the oceans accelerated global warming and marked the negative δ¹³C spike observed in marine carbonates, documenting the onset of the mass extinction period. The rapidity of the methane hydrate emission lasting from several years to thousands of years was tempered by the equally rapid oxidation of the atmospheric and oceanic methane that gradually reduced its warming potential but not before global warming had reached levels lethal to most life on land and in the oceans. Based on measurements of gases trapped in biogenic and abiogenic calcite, the release of methane (of ∼3–14% of total C stored) from permafrost and shelf sediment methane hydrate is deemed the ultimate source and cause for the dramatic life-changing global warming (GMAT > 34 °C) and oceanic negative-carbon isotope excursion observed at the end Permian. Global warming triggered by the massive release of carbon dioxide may be catastrophic, but the release of methane from hydrate may be apocalyptic. The end Permian holds an important lesson for humanity regarding the issue it faces today with greenhouse gas emissions, global warming, and climate change.

Read more (Paywalled): http://ift.tt/2nb3MaQ

One theory for the cause of the Permian Extinction Event is the eruption of the Siberian Traps, a gigantic million year long volcanic eruption which covered 770,000 square miles of Siberia in 100s of thousands of cubic miles of flood basalt lava.

I know human emissions produce the occasional impressive smoke haze, but I think I’ll go with Professor Wadhams on this one. It does seem a little wild to compare what we do to the atmosphere, to a colossal volcanic eruption which lasted a million years.