A successful climate agreement next December should reaffirm the two-degree cap on warming; include national “decarbonization” commitments up to 2030 and deep-decarbonization “pathways” (or plans) up to 2050; launch a massive global effort by both governments and businesses to improve the operating performance of low-carbon energy technologies; and provide large-scale and reliable financial help to poorer countries as they face climate challenges. The United States, China, the European Union’s members, and other countries are already signaling their intention to move in the right direction.