We consider the role of integrated assessment models (IAMs) in estimating the social cost of carbon (SCC) for U.S. regulatory purposes. Our approach is rooted in the needs of U.S. institutions responsible for making and implementing climate policy, specifically regulatory agencies within the Executive Branch and Congress should it choose to take up climate legislation. We argue, first, that policy makers need a numerical value for the SCC for policy evaluation and implementation. This cannot be done credibly without sophisticated computer models that incorporate climate and economic considerations, that is, without IAMs. Second, whatever the true value of the SCC is, it is not zero. Third, considerable uncertainty surrounds the current state of scientific knowledge about the costs of climate change. The evolving nature of the science and the ultimate goal of informing first‐best policy suggests to us that the official SCC used for regulatory analysis by the U.S. Government should not be thought of as a single number or even a range of numbers, but more broadly as a process that yields updated estimates of those numbers and ranges. Viewed in this way, the ultimate goal of the process is scientific credibility, public acceptance, and political and legal viability.