New report raises social cost of carbon estimates, surpassing previous estimates by more than 250%.
By Joshua Bledsoe, Kevin Homrighausen, and John Detrich
On December 2, 2023, the US Environmental Protection Agency (EPA) released a final report that substantially increases estimates of the social cost of greenhouse gases (GHG), including carbon dioxide, methane, and nitrous oxide (collectively, SC-GHG). The report describes SC-GHG as “the monetary value of the net harm to society from emitting one metric ton of that GHG into the atmosphere in a given year.”[1] The new estimates are intended to serve as a tool for decision-makers, aiding in the cost-benefit analysis of actions that would reduce or increase GHG emissions. Indeed, federal agencies are expected to use the estimates in future rule-makings and in the environmental review of forthcoming projects.




On August 25, 2022, the California Air Resources Board (CARB) unanimously approved regulations that require all new 2035 and later passenger vehicles to be zero-emission vehicles. The agency’s “Advanced Clean Cars II” regulations require manufacturers to deliver an increasing percentage of zero-emission vehicles each year, starting with 35% of new vehicle sales for cars, pickup trucks, and SUVs in 2026, and ramping up each year to reach 100% new vehicle sales by 2035.
On August 12, 2022, California Governor Gavin Newsom submitted five climate proposals (the Climate Proposals) to the California legislature in the waning days of California’s legislative cycle. In his statement following the transmittal, Newsom explained that “[w]e’re taking all of these major actions now in the most aggressive push on climate this state has ever seen because later is too late.”
On June 8, 2022, Canada launched the Greenhouse Gas (GHG) Offset Credit System (the System) to create a “market-based incentive to undertake innovative projects that reduce greenhouse gases.”
On June 30, 2022, the US Supreme Court issued its long-awaited ruling in West Virginia v. EPA — the consolidated petitions addressing EPA’s authority to regulate existing power plant greenhouse gas (GHG) emissions under Section 111(d) of the Clean Air Act (CAA). In a 6-3 opinion drafted by Chief Justice Roberts, the Court ruled against EPA, holding that EPA’s attempt to force an overall shift in power generation from higher-emitting to lower-emitting sources exceeded EPA’s statutory authority. Indeed, the Court noted that such a sweeping transformation of the nation’s power sector implicated a “major question” requiring explicit congressional authorization, that the Court argued the CAA did not provide.