Climate change is a threat not only to prosperity in the United States but also to national security, foreign policy, and development objectives throughout the world. Hurricane Sandy served as a reminder of the destruction to life and property from extreme weather events, which are likely to become more frequent and severe. Likewise, extended drought in the Southwest illustrates how climate change could affect agriculture, energy, recreation, and other major sectors of the US economy. The implications of climate change for the development prospects of poor countries are even worse. Lacking infrastructure, financial assets, insurance mechanisms, or strong institutions to cushion the impacts, developing societies remain highly vulnerable to natural disasters, including those resulting from increasingly irregular climatic conditions. The poorest households are most vulnerable — their houses often perch on steep, landslide-prone hillsides around cities or in coastal floodplains, and smallholder farmers lack irrigation and depend on increasingly erratic seasonal rains.