Whereas Weisbach and I both accept the basic scientific consensus on climate change, favor “aggressive” emissions reductions, see political inertia from Rio to Copenhagen as a lamentable policy failure, and endorse a precautionary approach, this convergence put him sharply at odds with many of his natural allies. Most neoclassical economists reject aggressive reductions, and many realists see them as politically infeasible. Though an outlier, Weisbach typically glosses over such internal disputes. Nevertheless, in my view, understanding them is essential for assessing the appeal of economic realist ideology, not least because the roots of the internal disputes are typically ethical.
Though Weisbach’s actual climate policy is couched in tough, apparently uncompromising language that will appeal to many environmentalists, I remain unsure how robust the position and arguments are. On the surface, Weisbach promises “aggressive reductions in emissions” (49) “far more ambitious than those currently on the table” (9), including zero emissions in the “not-too-distant future,” “even if the temperature turns out to be relatively insensitive to greenhouse gases and even if the harms turn out to be on the lower end of the possibilities.” Still, given the shunning of ethics, we should expect important gaps in the arguments.
Consider, for example, zero emissions “in the not-too- distant future.” Weisbach concedes that he cannot give a precise date, and then goes on to argue that it is somewhere between 2020 and 2150. Yet this range is enormous, and zero in five years and zero in 135 are dramatically different policy goals. Weisbach himself plumbs for the rather conservative target of 2100,4 suggesting “starting now and goingslowly is the best bet.”5 Still, this is done without much explanation, and it is unclear how it results in emissions reductions “far more ambitious than those currently on the table” (e.g., the Copenhagen Accord targeted 50% on 1990 levels by 2050, with at least 80% in the developed countries). It is also not obvious why unusually stringent targets would be warranted or feasible. Consider, for instance, Weisbach’s claim that radically fast decarbonization would be justified even if climate sensitivity turns out to be very low. Suppose “very low” means something resulting in a temperature rise of 1°C by 2100 (i.e., the bottom end of IPCC projections). 1°C is significantly below Copenhagen’s
1.5°-2°C benchmarks, and many scientists would regard it as “manageable” through adaptation. Consequently, such an unusually stringent target is likely to be seriously controversial, especially among economic realists (why not “invest” elsewhere?). Moreover, although I have more sympathy for Weisbach’s precautionary approach (usually regarded as anathema by CBA’s partisans),6 in my view it requires ethical underpinnings.