This paper studies the effect on CO2 emissions of the various agreements that follow the Long-Range Transboundary Air Pollution Convention and are related to acid rain problems. The analysis is based on a panel dataset of 150 countries over the period 1970–2008 and deals with the problems linked to the analysis of multiple agreements (e.g., time and membership overlap). We show that ratifying an additional treaty has a significant and negative impact on the level of CO2 emissions, even if it is not targeted toward CO2.