Left-wing political hack Michael Mann suggests that if Obama approves the Keystone pipeline "that could be enough to put us over the oft-quoted "dangerous" planetary warming of 2C"

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[Michael E. Mann] thanks David. Here's the full quote that I gave the reporter, provides some further context: The calculation appears to be based on some rather rosy assumptions. Swart and Weaver in Nature Geoscience (attached) show that the total Alberta tar sands yield is 2.38x 10^17 g Carbon. That's enough carbon dioxide emissions to induce a global mean temperature increase of as much as 0.5C. Given that we are committed already to about 1.5C warming even based on emissions to date, that could be enough to put us over the oft-quoted "dangerous" planetary warming of 2C. Their calculation doesn't even take into account the energy cost of refining and transportation, i.e. the total carbon footprint (and resulting warming) is almost certainly larger.