This working paper assesses how double counting of emission reductions can occur and how it could be addressed. This is an issue because if emission reductions are double counted, actual global greenhouse gas (GHG) emissions could be higher than the sum of what individual countries report. It is argued that the double counting of emission reductions would also make mitigation efforts less comparable and could discourage the use of market-based approaches to mitigate climate change.

The paper argues that double counting can occur not only directly, but in rather indirect ways which can be challenging to identify and that addressing double counting effectively requires international coordination in three areas: accounting of units, design of mechanisms that issue units, and consistent tracking and reporting on units. The paper discusses different options and makes specific recommendations for rules to address double counting up to 2020 and in a post-2020 climate regime.