On the efficiency of climate policies international coordination. This article analyses the economic efficiency of climate policies international coordination acknowledging long term perspectives and political constraints. It questions the economic and political viability of emission trading with respect to market power and dynamic distortions. The latter proves more worrying. While one may reasonably expect national positions being decentralized, the Climate Convention cannot commit on long term emission objectives. As a consequence, there is room for strategic behaviour by governments. Structural public programs, crucial to curb long term emissions, are likely to be scaled down because governments expect post-2012 quotas to be revised according to observed trends. This might jeopardize the climate action and further weaken the political consensus it requires. Are carbon taxes a better policy option ? It might be the case provided the tax is levied at the international level, but this option faces political obstacles. A hybrid scheme should realise a good compromise between economic efficiency and political acceptability.