Michael J. Benton, paleontologist: Runaway Greenhouse

Benton, M.J. Presidential Address 2007: The end-Permian mass extinction events on land in Russia. Proceedings of the Geologists’ Association Volume 119, Issue 2, 2008, Pages 119-136

Conclusion: If the runaway greenhouse model is correct and explains perhaps the biggest crisis on Earth in the last 500 Ma, it is a model worth exploring further. It appears to represent a breakdown in global environmental mechanisms, where normal systems that would equilibrate atmospheric gases and temperatures took hundreds of thousands of years to come into play. Models for ancient extinction events affect the current debate about global warming and its possible medium-term consequences. Some scientists and politicians look to the sky for approaching asteroids that will wipe out humanity. Perhaps we should also consider how much global warming can be sustained and at what level the runaway greenhouse comes into play.

Abstract: The mass extinction of life in the sea and on land 251 million years ago, at the Permian-Triassic boundary, was undoubtedly the largest mass extinction of all time. Sedimentological and geochemical evidence show that global temperatures rose, that there was extensive oceanic anoxia, and that there was massive erosion of sediment, especially soils, from the land. These phenomena might have been a consequence of the massive eruptions of the Siberian Traps, which produced carbon dioxide – a greenhouse gas – as well as acid rain, which killed plants and led to stripping of soils. Field work in Russia over the past decade has shown evidence for massive erosion at the boundary, and for the nature of ecosystem collapse and slow recovery after the event.

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