Recap

Greenhouse Extinctions

Professor of Earth and Space Sciences and Astrobiologist for NASA, Peter Ward (Book Link) discussed his vision of the end of the world based on past mass extinctions.

While most scientists agree that a meteor impact killed the dinosaurs 65 million years ago, Ward said our planet's 15 other ancient mass extinctions were caused by short-term global warming. According to Ward, high levels of CO2 increased global temperatures, contributing to conditions that gave rise to a series of bacteria in the oceans that produced toxic hydrogen sulfide gas. Eventually, this gas erupted into the atmosphere and poisoned animals and plants on the planet's surface.

Atmospheric CO2 is currently at 380 ppm and rising 2 ppm every year, Ward explained. He said the geological record indicates 'greenhouse extinctions' occur when CO2 levels go beyond 1000 ppm and when all the ice caps have melted. Ward estimated that we have 1000 years before this mass extinction process begins, unless we begin reducing man-made CO2 emissions now. In the meantime, we can expect a host of problems, including coastal flooding and food shortages, caused by rising sea levels, he warned.

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Impact from the Deep

In his October 2006 Scientific American article, Impact from the Deep, Peter Ward argues that our planet's ancient mass extinctions were caused, not by asteroid impacts, but by hydrogen sulphide eruptions from the sea due to global warming. According to Ward, we may be at the doorstep of yet another extinction -- this time our own. Read more at sciam.com.