This Article discusses the Trump Administration’s main actions to undermine the role of science in public policy and the consequences for cost-benefit analysis involving climate change policies. It analyzes the specific attacks on science and their impact on relevant policies, namely, the rollbacks of the Clean Water Rule, the pesticides ban, the Clean Air Act, and the Clean Power Plan, as well as modification of the National Environmental Policy Act and regulations promoting fuel efficiency, and the flexibilization of environmental enforcement during the COVID-19 pandemic. All of these deregulatory cases were also illustrative of at least one modality of an attack on science. It concludes by examining the negative impact of the war on science and related unreasoned policymaking that transcends domestic borders.