11 November 2009 [Your questions]
IPCC AR4 and the runaway greenhouse effect
26. The IPCC Fourth Assessment Report claims that "anthropogenic warming could lead to some impacts that are abrupt or irreversible." However, I have read that CO2 levels were once much higher on earth in the past. Why did the earth's atmosphere not experience "runaway" positive feedbacks during those eras?
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Answered 11 November 2009.
Question author: Harold Vance.
Asked 5 November 2009.