Coalition size determines costs post-Kyoto policies after 2012

Abatement costs of post-Kyoto policies after 2012 are relatively modest in the case of a global coalition with unrestricted emissions trading. Costs will rise considerably if the coalition becomes smaller. In the case of smaller coalitions, the use of the Clean Development Mechanism (CDM) will lower abatement costs. Yet, carbon leakage may produce an outcome with less emission reductions than intended.