Self-enforcing international environmental agreements and trade: taxes versus caps

This paper studies within a multi-country model with international trade the stability of international environmental agreements (IEAs) when countries regulate carbon emissions either by taxes or caps. Regardless of whether coalitions play Nash or are Stackelberg leaders the principal message is that the choice of caps or taxes matters. International trade and tax regulation turn out to be necessary conditions for the existence of the encompassing self-enforcing IEA, and that the latter is attained the more likely, the less severe the climate damage. Hence, cap regulation is inferior to tax regulation insofar as in case of the former there exist no large and effective self-enforcing IEAs, in particular not the encompassing self-enforcing IEA. Further results are that for the formation of encompassing self-enforcing IEAs it does not matter (much) whether climate coalitions play Nash or are Stackelberg leaders or whether fossil fuel is modeled as a consumer good or an intermediate good.