Recent developments in the political, scientific and economic debate on climate change suggest that it is of critical importance to develop new approaches able to compare policy scenarios for their environmental effectiveness, their distributive effects, their enforceability, their costs and many other dimensions. This paper discusses a quantitative methodology to assess the relative performance of different climate policy scenarios when accounting for their long-term economic, social and environmental impacts. The proposed procedure is based on Data Envelopment Analysis, here employed in evaluating the relative efficiency of eleven global climate policy scenarios. The methodology provides a promising comparison framework; it can be seen as a way of setting some basic guidelines to frame further debates and negotiations and can be flexibly adopted and modified by decision makers to obtain relevant information for policy design. Three major findings emerge from this analysis: (i) stringent climate policies can outperform less ambitious proposals if all sustainability dimensions are taken into account; (ii) a carefully chosen burden-sharing rule is able to bring together climate stabilisation and equity considerations; and (iii) the most inefficient strategy results from the failure to negotiate a post-2012 global climate agreement.