The Paris Agreement can be strengthened by a treaty limiting global fossil fuel supply During decades of international climate policy negotiations, aiming to limit demand for fossil fuels, the stock of carbon dioxide in the atmosphere has increased considerably, and even the flow of emissions to the atmosphere continues to grow ( 1 ). To reach the Paris Agreement's goal of keeping global warming well below 2°C, substantial parts of the world's fossil fuels simply cannot be combusted and must be left in the ground ( 1 , 2 ). Recent work thus suggests redirecting climate policies toward fossil fuel producers directly ( 3 – 5 ) by capping the flows of extraction and restricting the stocks of resources available for exploration. We synthesize key economic mechanisms that support this approach, arguing that an international treaty among fossil fuel–producing countries could (i) enhance the impact of the Paris Agreement in the presence of free riders; (ii) stimulate investment in low-carbon technology research and development (R&D); (iii) provide insurance against a failed Paris Agreement; and (iv) make carbon policies more acceptable to fossil fuel producers, thus increasing their support. None of these effects depend on universal producer participation. Moreover, such a treaty need not be costly and could in fact help reduce the costs of the required transition to a low-carbon economy.