Recap

Climate & Extinction

Investigator for the NASA Astrobiology Institute, Prof. Peter Ward discussed his new book, Out of Thin Air, which shows how fluctuating oxygen levels have contributed to mass extinctions and evolutionary changes over millions of years. For instance, dinosaurs the size of chickens, flourished during a 20-million-year period of low oxygen-- it wasn't till oxygen levels grew higher that the larger dinosaurs developed, he explained.

He cited the dangers of rising carbon dioxide levels as well as hydrogen sulfide, both of which could contribute to extinctions of life. Hydrogen sulfide is particularly insidious, he noted-- as oxygen levels drop, massive bacteria forms in ocean waters turning them into dead zones in which no fish or animal life can exist. A small asteroid hitting Earth could also wreak havoc on the planet, he said. It would send particulates into the atmosphere, throw off agricultural cycles and lead to massive famines.

Ward reported that one of the biggest climate problems is the melting of the ice caps: The rise in sea level could displace millions, such as those living in a low lying country like Bangladesh, and could provoke wars over food. Interestingly, he noted that because of global warming, the sky will actually take on a greenish tint in the years to come. For more scientific discourse on climate issues, he recommended the website realclimate.org.

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Heading into Extinction?

The chart on the left (view in full) shows how rising carbon dioxide levels are associated with mass extinctions and that based on projections we could be heading into another such period. The graphic appears in Peter Ward's article, Impact from the Deep in the October issue of Scientific American.