Thursday, November 13, 2008

More on Whether a Big Chill Is Nigh - Dot Earth Blog - NYTimes.com
[Jim Hansen:] It would take only a small further reduction in climate forcing (less long-lived GHGs or whatever) to yield more ice during the glacial phase of glacial-interglacial oscillations. But that is entirely academic at this point, unless humans go extinct. Although orbital variations instigate the glacial-interglacial swings, the mechanisms for climate change are changes in GHG amount and surface albedo (as we show in Fig. 1 of our paper) — those mechanisms are now under the control of humans. Another ice age cannot occur unless humans go extinct. It would take only one CFC factory to avert any natural cooling tendency. Our problem is the opposite: we cannot seem to find a way to keep our GHG forcing at a level that assures a climate resembling that of the past 10,000 years.
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[Dan Schrag:] I am very, very skeptical. This is all fun and games with a climate model.
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[Revkin:] As I’ve written before, Homo sapiens appears to be in the uncomfortable position of being the first life form to exert a global-scale influence (for better or worse) and be aware of that reality (plants altered the atmosphere, too, but most likely didn’t realize it).

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