A carbon tax versus clean subsidies: Optimal and suboptimal policies for the clean transition

A three-sector – services, clean and dirty - integrated assessment model with endogenous technology is described. Optimal policy leads to a period of intense clean research and requires a carbon tax and clean research subsidies. Using multiple calibrations, I explore the relative performance of these instruments when acting alone, along with a clean production subsidy and a dirty research tax. A carbon tax wins in most, but if optimal policy occurs after 2050, each instrument wins in some calibrations. Both a carbon tax and a clean production subsidy should apply if research instruments are unavailable. (JEL O30, O44, Q54, Q56, Q58).