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 panel’s reports. Central banks established a Network for Greening the Financial System that now requires more than 140 supervisors to stress-test banks against IPCC-derived futures. Asset managers wrote trillions of dollars in environmental, social, and governance funds on the assumption that the panel’s high-end scenario described the world’s likely path. Local governments along American and European coastlines planned seawalls and zoning rules around IPCC sea level numbers. Insurance companies repriced risk on the same models.
That assumption has now collapsed. In April 2026, the scenario committee that supplies the IPCC’s Seventh Assessment Report, known as ScenarioMIP, published a paper that concluded that “on the high-end of the range, the CMIP6 high emission levels (quantified by SSP5-8.5) have become implausible…” In other words, the worst-case future that has anchored climate science for fifteen years describes a world that cannot exist. Scenario “RCP 8.5,” and its successor SSP5-8.5, generated more than half of the references in the 2018 U.S. Fourth National Climate Assessment. They accounted for nearly 60% of the references in the IPCC’s Special Report on the Ocean and Cryosphere. Thirty new studies per day are published based on RCP 8.5.
