Climate Change Catastrophes

Most studies that compare price and quantity controls for greenhouse gas emissions under uncertainty find that price mechanisms perform substantially better. In these studies, the benefits from reducing emissions are proportional to the level of reductions, and such linear benefits strongly favor price policies (Weitzman 1974). Catastrophic damages, however, challenge that intuition as consequences become highly nonlinear. Catastrophe avoidance offers huge benefits, and incremental adjustments on either side of the associated threshold are relatively unimportant, suggesting a strong preference for quantity controls. This paper shows that with catastrophic damages, both price and quantity mechanisms offer large gains over the business-as-usual alternative, and the difference between policies is never more than 10%. Catastrophe avoidance is much more important than efficient catastrophe avoidance. Although previous studies favoring price policies in the presence of uncertainty have worried that catastrophes would reverse their results, this analysis indicates that such concerns are not borne out.