"Prices versus quantities" (Weitzman 1974), a hugely influential paper, is widely cited (and taught) in current debates about the best policy to reduce greenhouse gas emissions. The paper's criterion for ranking policies suggests that technological uncertainty favors taxes over cap and trade....

We study clean energy subsidies in a quantitative climate-economy model. Clean energy subsidies decrease carbon emissions if and only if they lower the marginal product of dirty energy. The constrained-efficient subsidy equals the marginal external cost of dirty energy multiplied by the marginal...

We study clean energy subsidies in a quantitative climate-economy model. Clean en-ergy subsidies decrease carbon emissions if and only if they lower the marginal product of dirty energy. The constrained-efficient subsidy equals the marginal external cost of dirty energy multiplied by the...