Flattening the carbon extraction path in unilateral cost-effective action

Internalizing the global negative externality of carbon emissions requires the flattening of the extraction path of world fossil energy resources (=world carbon emissions). We consider governments with sign-unconstrained emission taxes at their disposal and seeking to prevent world emissions from exceeding some binding aggregate emission ceiling in the medium term. Such a ceiling policy can be carried out either in full cooperation or by a sub-global climate coalition. Unilateral action has to cope with carbon leakage and high costs, which makes a strong case for choosing a policy that implements the ceiling in a cost-effective way. In a two-country, two-period general equilibrium model with a non-renewable fossil-energy resource, we characterize the unilateral cost-effective ceiling policy and compare it with its fully cooperative counterpart. We show that with full cooperation there exists a cost-effective ceiling policy in which only first-period emissions are taxed at a rate that is uniform across countries. In contrast, the cost-effective ceiling policy of a sub-global climate coalition is characterized by emission regulation in both periods. The share of the total stock of energy resources owned by the sub-global climate coalition turns out to be a decisive determinant of the sign and magnitude of unilateral cost-effective taxes.