There are, generally speaking, two types of harm from climate change: harm to human health, economic prosperity and welfare, and harm to nonhuman species and ecosystems. In this chapter, I discuss how the human cost of climate change has been estimated for US regulatory purposes. This estimate is called the social cost of carbon (SCC). It is the most rigorous monetized measure of the harm to human economies from climate change. Harm to humans is not the only potential harm from changing climate, but as the quantification of such avoided harm was the primary benefit advanced to justify Obama-era climate change regulations, I focus here solely on the SCC.