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Comments on U.S. Army Corps of Engineers Environmental Impact Statement

President Trump’s recent executive order on energy disbands the Interagency Working Group on the Social Cost of Carbon (IWG) and withdraws its technical support documents that underpin the IWG’s range of estimates. Instead, the executive order directs federal agencies to continue to monetize the social cost of carbon emissions pursuant to the Office of Management and Budget’s Circular A-4. In our comments, we highlight that the range of estimates from the IWG that agencies have been using, including the number used by the U.S. Army Corps of Engineers in the Draft Environmental Impact Statement, is consistent with Circular A-4 and therefore, consistent with the executive order.

Policy Integrity, along with our partners, encourage the Corps—and all federal agencies—to continue valuing the social cost of greenhouse gases in environmental impact statements and do so as thoroughly, accurately, and transparently as possible, drawing from the best available scientific and economic data and methodologies.

In our comments, we also argue that a global estimate for the SCC is consistent with OMB’s guidance. We also make the case that, when calculating the SCC, using a 3% or lower discount rate for inter-generational effects—or a declining discount rate—is consistent with Circular A-4. Finally, we emphasize that this guidance also requires plausible assumptions about uncertainty and note that all existing best estimates of the social cost of greenhouse gases are almost certainly underestimates and should be treated as a lower bound.