Bill McKibben has penned a more-in-sorrow-than-anger piece (“Hot Mess”) in the current issue of the magazine, shaking his head at conservatives’ failure to adopt his position on global warming. (It is an almost exact recapitulation of Al Gore’s argument in TNR a few months ago, to which I also replied). In the simplest terms, McKibben leaps from the proposition that CO2 accumulations are very likely to cause global warming to the assertion that the projected amount of warming will cause enough damage to justify a worldwide program of emissions mitigation that he says will be “most difficult thing we’ve ever done.” Where is his evidence?
According to the currently governing Fourth Assessment Report produced by the United Nations Intergovernmental Panel on Climate Change (IPCC), under a reasonable set of assumptions for global economic and population growth (Scenario A1B), the world should expect to warm by about 3°C over roughly the next century (Table SPM.3). Even in the most extreme IPCC marker scenario (A1F1), the best estimate is that we should expect warming of about 4°C over roughly the next century. How bad would that be? Also according to the IPCC (page 17), a global increase in temperature of 4°C should cause the world to have about a 1 to 5 percent lower economic output than it would otherwise have. So, if we do not take measures to ameliorate global warming, the world should expect sometime in the twenty-second century to be about 3 percent poorer than it otherwise would be (though still vastly richer per capita than today).
This is the crux of problem with McKibben’s argument: According to the IPCC, the expected economic costs of global warming are about 3 percent of GDP more than 100 years from now. This is pretty far from the rhetoric of global devastation that McKibben, and so many others, use.
McKibben can use all the scare terms he wants, but this is not a prima facie case that we should want governments to reengineer the energy sector of the global economy coercively around the primary goal of lowering these projected future damages at the expense of, for example, more rapid worldwide economic growth. And, as I explained in my detailed reply to Gore, even the argument that “Yes, but future damages might be even worse than current forecasts” is a real stretch—at a minimum, it is the basis for a non-obvious technical debate that doesn’t fall into the “let’s shake our heads at these dumb-ass Republicans” category.
One of the great strengths of TNR, in my opinion as an outsider, is that it has made a habit of facing up the strongest arguments of its ideological opponents. McKibben does the opposite. Like Gore’s piece, “Hot Mess” is comfort food for liberals.