Killer Greenhouse Effect (or Pardon my Anoxia): A Note from Luke
Luke Walker reminds us that geological history includes evidence of mass extinctions from “killer greenhouse conditions”:
“Readers of this blog are often witness to accusations of alarmism by those opposed to scenario projections using contemporary anthropogenic global warming theory.
Comfort is often taken in the world having survived substantial climate swings in geological time and that some species such as reef building corals have come through that turmoil.
So it is with some irony that the October 2006 issue of Scientific American has a major article by Professor Peter Ward at the University of Washington suggests that extinction events in geological history have been caused by killer greenhouse conditions. What’s this – geological alarmism? Is nothing sacred?
“More than half life on the earth has been wiped out, repeatedly, in mass extinctions over the past 500 million years. One such disaster, which includes disappearance of the dinosaurs, is widely attributed to an asteroid impact, but others remain inadequately explained.
New fossil and geochemical evidence points to a shocking environmental mechanism for the largest of the ancient mass extinctions and possibly several more: an oxygen depleted ocean spewing poisonous gas as a result of global warming”
Apparently five times over the last 500 million years most of the world’s life forms have ceased to exist. End of the Ordovician 443 My ago; close of the Devonian 374 My; the Great Dying at the end of the Permian 251 My where 90% of ocean dwellers and 70% of land dwellers were obliterated; the end of the Triassic 201 My; and the end of the Cretaceous at 65 My with a likely asteroid impact.
However, new analyses are showing that some sudden extinctions were not that sudden lasting several hundred thousands of years.
It theoretically works something like this:
1. Volcanic activity releases carbon dioxide and methane
2. Rapid global warming occurs
3. Warm ocean absorbs less oxygen
4. Anoxia destabilises the chemocline where oxygenated surface waters meet H2S permeated waters in the ocean, anaerobic bacteria flourish
5. Hydrogen sulphide gas (H2S) gas upwells through the ocean as the chemocline rises to the ocean surface
6. Green and purple sulphur bacteria in the surface ocean thrive while oxygen breathers suffocate
7. H2S gas kills land animals and plants.
8. H2S destroys the ozone shield
9. Ultra violet radiation from the sun kills remaining life.
“A minor extinction at the end of the Palaeocene 54My ago was already – presciently – attributed to an interval of oceanic anoxia somehow triggered by short-term global warming.” Evidence is also present at the end of Triassic, middle Cretaceous, and late Devonian.
So are these extreme greenhouse effect extinctions possibly a recurring phenomenon in the earth’s history. Atmospheric CO2 was 1000ppm when extinctions began in the Palaeocene. “
So if the modern earth got close to 1000ppm this might represent something for our children to deal with. But maybe that’s just geological alarmism for you.
I’m getting a Lotto syndicate going called “Killer Greenhouse”.
Climate simulation of the latest Permian: Implications for mass extinction by Jeffrey T. Kiehl & Christine A. Shields Climate Change Research Section, National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, Colorado 80305, USA
Abrupt and Gradual Extinction Among Late Permian Land Vertebrates in the Karoo Basin, South Africa
Science 4 February 2005:Vol. 307. no. 5710, pp. 709 – 714 by Peter D. Ward,1* Jennifer Botha,3 Roger Buick,2 Michiel O. De Kock,5 Douglas H. Erwin,6 Geoffrey H. Garrison,2 Joseph L. Kirschvink,4 Roger Smith3
Photic Zone Euxinia During the Permian-Triassic Superanoxic Event, Science 4 February 2005:
Vol. 307. no. 5710, pp. 706 – 709 by Kliti Grice, Changqun Cao, Gordon D. Love, Michael E. Böttcher, Richard J. Twitchett, Emmanuelle Grosjean, Roger E. Summons, Steven C. Turgeon, William Dunning,Yugan Jin
Massive Release of Hydrogen Sulphide to the Surface Ocean and Atmosphere during intervals of Oceanic Anoxia. Kump, L.R., Pavlov, A., Arthur, M.A. Geology: 33:5:397-400. May 2005.”
Thanks Luke. And I’m going to add to your reading list: The Past is the Key to the Present: Greenhouse and Icehouse Over Time by Prof Ian Plimer, IPA Review, Vol 55, No. 1. March 2003, pgs. 9-12.