March 15, 2024 To: Department of Energy

To monetize climate benefits, DOE applies estimates of the social cost of greenhouse gases (SC-GHG) from the Interagency Working Group on the Social Cost of Greenhouse Gases (Working Group).4 Although the Working Group’s climate-damage valuations reflected “the best science available at the time of that process,”5 they are now a decade old. [...] As EPA explained, the “climate change literature and the science underlying the economic damage functions have evolved” since the Working Group’s last substantive updates in 2013.28 Whereas the research underlying the Working Group’s damage functions was published in the 1990s and 2000s, many economic studies have since been published.29 See the figure on the next page for an illustration the time. [...] EPA’s Estimates Improve Upon Limitations in the Working Group’s Estimates that DOE Acknowledges in the Proposed Rule EPA’s climate-damage estimates are not just the best available—they correct for specific limitations in the Working Group’s valuations that DOE recognizes in the Proposed Rule. [...] In the Proposed Rule’s technical support document, DOE acknowledges that the Working Group’s valuations incorporated “the best science available at the time of that process”49 but that “the socioeconomic and emissions scenarios used as inputs to the models do not reflect new information from the last decade of scenario generation or the full range of projections.”50 As discussed above, EPA’s estim. [...] at 14-1 (“As a member of the IWG involved in the development of the February 2021 SC-GHG TSD, DOE agrees that the interim SC-GHG estimates represent the most appropriate estimate of the SC-GHG until revised estimates have been developed reflecting the latest peer-reviewed science.”).