Climate debate and policy proposals in the United States have yet to grasp the gravity and magnitude of the challenges posed by global warming. This paper develops three arguments to redress this situation. First, the spatial and temporal scale of the processes linking greenhouse gas (GHG) emissions to climate change is unprecedented in human experience, challenging our abilities to comprehend, let alone act. An adequate understanding of the scale of global warming leads to an unequivocal starting point for all discussions: we must leave as much fossil fuel in the ground as possible, for as long as possible. Second, a policy informed by this insight must focus on the built environment, which mediates economic production, exchange, and consumption in ways that both presuppose and reinforce high rates of GHG emissions, especially in the U.S. A rapid and comprehensive reconfiguration of the built environment is imperative if we are to mitigate and adapt to global warming. Third, the obstacles and opposition to such a reconfiguration are best understood in terms of the devaluation of fixed capital, public and private investments alike, that has been sunk in the built environment of the present. In a fortuitous paradox, these investments are threatened with devaluation whether or not we act to stabilize the atmospheric GHG concentrations; in highly uneven, unpredictable, and potentially abrupt ways, global warming will make our current built environment increasingly untenable and uneconomical. There is, therefore, no reason not to be proactive and to craft policies with the goal of completely redesigning and rebuilding our built environment over the next 20 to 50 years.