4°C

Conventional climate change wisdom tells governments to plan for a 2°C increase in global average temperature. However, increasingly robust science indicates that the planet is well on its way to at least 4°C of warming, possibly by the end of the 21st century or shortly thereafter. That much warming is a governance game changer, taking the multiple interconnected and complex systems that define U.S. society across thresholds and tipping points into cascades of transformational change. Critically, these potentially include the United States’ system of government—the key system that must successfully adapt to the coming changes in order for the country as a whole to have any chance of adapting peacefully, equitably, and productively to systemic transformation while still remaining a democracy.

This Article seeks to push U.S. climate change adaptation policy toward an entirely new mode of governance necessary to meet the challenges ahead. It does so by making five novel arguments. First, it assembles recent scientific climate change studies to show that a 4°C warmer future is currently the planet’s most likely trajectory. Second, it argues that being on that trajectory necessitates the dissociation of climate change mitigation and adaptation goals so that adaptation policy is free to address this more dire future. Third, it summarizes recent science to demonstrate that 4°C of warming poses a categorically different adaptation challenge than 2°C, as in situ adaptation becomes increasingly impossible, inducing both species and large numbers of people to migrate within U.S. boundaries. Fourth, to deal with these migrations and their attendant needs and consequences, this Article describes both a new mode of climate change adaptation, called “redesign” adaptation, and the governance tools available to coordinate, promote, and guide the equitable and productive resettlement of the United States. Finally, this Article argues that the United States, with strong leadership and funding from the federal government, needs to initiate anticipatory governance practices now to facilitate redesign adaptation in the future, beginning with a new national foresight research program.