A central component of the new United Nations Framework Convention on Climate Change (UNFCCC) climate agreement, to be adopted by 2015, will be national mitigation commitments undertaken by Parties after 2020. While opinions on this are varied, there has been a focus on the idea that mitigation commitments should be nationally determined, rather than negotiated, in order to encourage participation by all Parties and lead to greater overall reductions in green house gas (GHG) emissions. This paper assesses design issues related to the next set of national mitigation commitments based on the criterion of measurability, which includes considerations such as transparency, accountability, comparability, domestic GHG management, and accurate tracking of global emissions reductions.