Scientists, economists, and government officials have worked together to develop estimates of the costs to society of each additional ton of greenhouse gas emissions. Decisionmakers have, in turn, used these estimates to craft rules and policies, value the benefits of clean energy resources, and assess the environmental effects of proposed actions. Notably, between 2009 and 2016, the U.S. federal government’s Interagency Working Group on the Social Cost of Greenhouse Gases developed standardized estimates for use across federal government agencies. These estimates have been applied not only by the U.S. government, but also by Canada, Mexico, and a variety of state and local government agencies. The Trump administration has created a new “interim” estimate that obscures the vast majority of these climate damages, and has used this value to justify deregulatory actions. As the U.S. federal government turns away from the science and economics underlying climate change, the baton has been passed to states and municipalities, businesses, and other groups that can help ensure that climate impact estimates continue to reflect the best available science and economics.