Too Levered for Pigou: Carbon Pricing, Financial Constraints, and Leverage Regulation

We analyze jointly optimal carbon pricing and leverage regulation in a model with financial constraints and endogenous climate-related transition and physical risks. The socially optimal emissions tax is below the Pigouvian benchmark (equal to the direct social cost of emissions) when emissions taxes amplify financial con- straints, or above this benchmark if physical climate risks have a substantial impact on collateral values. Additionally introducing leverage regulation can be welfare- improving only if tax rebates are not fully pledgeable. A cap-and-trade system or abatement subsidies may dominate carbon taxes because they can be designed to have a less adverse effect on financial constraints.