Climate policy is gridlocked nationally and globally, with virtually no chance of a breakthrough under current conditions. Policy makers need to accept that societies will not make drastic changes to address climate change until a climate crisis hits. The recent financial crisis showed that when powerful special interests have convinced much of the public that what they are doing is not dangerous, only a disaster that discredits those interests will provide an opportunity for comprehensive policy change. Societies that have response plans on the shelf will be far better off than those that are blindsided. The task for national and regional leaders, then, is to develop a set of contingency plans for possible climate shocks — what we might call, collectively, Plan Z. Such a plan should include detailed scenarios of plausible climate shocks; close analyses of options for emergency response by governments, corporations and nongovernmental groups; and clear specifics about what resources — financial, technological and organizational — we will need to cope with different types of crises.