There are a number of times in the geological history of the earth that a waming became selfsustaining, the PT extinction was just one of them.
There is ZERO evidence that warming caused the PT extinction. There's plenty that supports cold as a cause however.
LOL. Says you. While the whole of the geologic community states otherwise.
The Permo-Triassic (P-T) Extinction
In 1996 Henk Visscher and his colleagues reported extreme abundances of fossil fungal cells in land sediments at the P*T boundary. There are
hints that the fungi-enriched "layer" is the record of a single, world-wide crisis, with the fungi breaking down massive amounts of vegetation that had been catastrophically killed (there were no termites yet). Such a fungal layer is unique in the geological record of the past 500 m.y. The best evidence we have suggests that there were major extinctions among gymnosperms, especially in Europe, and among the coal-generating floras of the Southern Hemisphere. The vegetation of the early Triassic in Europe looks "weedy," that is, invasive of open habitats. Andrew Knoll and his colleagues have suggested that the extinction was caused by a catastrophic overturn of an ocean supersaturated in carbon dioxide. This would result in tremendous, close to instantaneous, degassing that would roll a cloud of (dense) carbon dioxide over the ocean surface and low-lying coastal areas. An analog might be the recent catastrophic degassing of Lake Nyos, in the Cameroon, where hundreds of people were killed as carbon dioxide degassed from a volcanic lake and cascaded down valleys nearby. The difference is that the proposed P*T disaster was global.
In this
scenario, the carbon dioxide build-up results from the global geography that included the gigantic ocean Panthalassa. Knoll and colleagues
speculated that the abnormal ocean circulation in Panthalassa did not include enough downward transport of oxygenated surface water to keep the deep water oxygenated. With normal respiration and decay of dead organisms, the deep water evolved into an anoxic mass loaded with dissolved carbon dioxide, methane, and hydrogen sulfide. Carbon continued to fall to the sea floor from normal surface productivity, but it was deposited and buried because there was no dissolved oxygen to oxidize it. As carbon dioxide levels fell in the atmosphere, the earth and the ocean surface cooled. Finally, the surface waters became dense enough to sink, triggering a catastrophe as the CO2-saturated deep waters were brought up to the surface, degassing violently. The event would trigger a greenhouse heating and a major climatic warming.
In 1998 Samuel Bowring and colleagues reported that the carbon isotope change at the P-T boundary in South China was probably very short-lived: a "spike" only perhaps 165,000 years long. This suggests a major (catastrophic?) addition of non-organic carbon to the ocean, rather than just a failure in the supply of organic carbon. They suggested three possible scenarios. Two of them are variants of the Siberian Traps scenario above, except that in addition the climatic changes could have set off an overturn of Panthalassa and a carbon dioxide crisis. Their third suggestion is an asteroid impact, but there is not much evidence for that.
Most recently, Greg Retallack and colleagues have found evidence in Australia that suggests a prolonged greenhouse warming set in right at the P-T boundary. Several paleoclimatic indicators suggest the same story, which
implies that the role of carbon dioxide was the vital link between any environmental disasters and the extinctions. Carbon dioxide in the atmosphere
could have been increased by volcanic eruptions, by oceanic turnover, and it would have been accentuated and prolonged if plants were killed off globally. (World floras and oceanic plankton would have to recover before the carbon dioxide could be drawn down out of the atmosphere.) We may be getting close to the answer here!
