Promoting learning among participants is a key function commonly attributed to international regimes. Such learning, however, cannot always be guaranteed, and regimes may sometimes descend into ossification. In contrast to a learning regime, an ossifying regime is one that is unable to process new information, facilitate the free-flow of new ideas, or foster understanding and trust among negotiators. Evidence from the recent history of the climate change regime suggests it is suffering from ossification. Dragging forces contributing to this include the institutionalization of the “north/south divide,” complexity of the process, fragile conditions for effective communication, onerous decision—making rules, activities of obstructionists, absence of the US, and weak implementation. Pockets of learning on climate change are, however, still active, especially outside the regime itself. To reinvigorate the negotiations, meaningful progress is needed on domestic and regional implementation, including ensuring the success of the Protocol's market mechanisms.