Governments, banks, and corporations across the developed world have for nearly four decades treated the United Nations Intergovernmental Panel on Climate Change (IPCC) as the final word on the science of climate change. The Obama and Biden administrations regulated carbon dioxide as a pollutant on the strength of IPCC findings. The European Union built its emissions trading system around IPCC scenarios. The United Kingdom anchored its 2008 Climate Change Act in projections drawn from the pan...