This short piece analyzes the background and content of the Copenhagen Accord on climate change, which was agreed to last December by leaders of roughly 25 countries, including all of the world's major economies. Although the Copenhagen Accord is a political rather than a legal instrument and has been criticized by some as inadequate or worse, it represents a potentially significant breakthrough. On one side, developed countries agreed to put significant new funds on the table for climate change mitigation and adaptation, both for the short and medium terms, and committed to implement national economy-wide emissions targets for the post -2012 period, which will be internationally listed. On the other side, developing countries agreed for the first time to reflect their national mitigation actions in an international instrument and to subject their actions to some form of international review. The failure of the conference as a whole to adopt the Accord leaves its future uncertain. But if the participating states actually carry through on what they negotiated in Copenhagen, the "bottom up" architecture of the Accord could help encourage and reinforce national actions. In any event, as the most that world leaders could accept through direct negotiations under an intense international spotlight, the Copenhagen Accord may well represent the high-water mark of the climate change regime for some time to come.