Our comment primarily concerns the DOE’s use of the social cost of carbon (SCC) in the cost/​benefit analysis of the Energy Conservation Program: Energy Conservation Standards for Residential Furnace Fans proposed rulemaking. The determination of the SCC is so discordant with the best scientific literature on the equilibrium climate sensitivity and the fertilization effect of carbon dioxide—two critically important parameters for establishing the net externality of carbon dioxide emissions—that, until this situation can be rectified, it should be barred from use in this and all other federal rulemaking.