The $51 to $190 Shift: How the Social Cost of Carbon Translates Future Climate Damage into Current Regulatory Policy

The U.S. Environmental Protection Agency and the Office of Management and Budget hold the authority to set the monetary value of future climate damages, a figure they must apply whenever drafting new federal regulations. When these agencies next finalize major rules on power plant emissions or vehicle efficiency standards, they will rely on a metric known as the social cost of carbon to justify the economic burden placed on industry.[1][3]

The social cost of carbon operates as a translation layer between atmospheric physics and cost-benefit analysis. It estimates, in dollars, the long-term economic damage caused by a single metric ton of carbon dioxide emitted into the atmosphere in a given year. This figure aggregates projected losses in agricultural productivity, human health impacts, property damage from increased flood risk, and changes in energy system costs.[2]

In February 2021, the Interagency Working Group on Social Cost of Greenhouse Gases re-established an interim metric of $51 per metric ton for emissions occurring in the year 2020, assuming a 3 percent discount rate. This figure restored the metric to its pre-2017 trajectory, adjusting for inflation, and served as the baseline for federal rulemaking across multiple agencies.[1]

"The IWG found that the SC-GHG estimates used under the previous administration failed to reflect the full impact of GHG emissions in multiple ways," the 2021 Technical Support Document states, noting that previous models ignored global damages and relied on outdated economic data.

However, the EPA's subsequent comprehensive report, finalized in late 2023, proposed a drastic upward revision. Incorporating newer scientific modeling on mortality and economic feedback loops, the EPA calculated the social cost of carbon at $190 per metric ton for 2020 emissions at a 2 percent near-term discount rate.[3]

The discount rate acts as the fulcrum of the entire calculation. It represents how much society values present costs over future benefits. A higher discount rate shrinks the present value of future climate damages, while a lower rate amplifies them. The Brookings Institution notes that shifting the discount rate from 3 percent to 2 percent mathematically doubles the resulting social cost of carbon, even before new physical damage estimates are applied.[2]

The leap from $51 to $190 is not merely an artifact of discount rates. The EPA's updated methodology integrated high-resolution data on how temperature shifts affect crop yields and human mortality. Previous models assumed a linear relationship between heat and economic output; newer damage functions capture the non-linear thresholds where agricultural systems fail and heat-related deaths spike.[3]

This metric directly determines which regulations pass legal muster. Under Executive Order 13990, agencies must conduct cost-benefit analyses for significant regulatory actions. If a proposed rule costs industry $10 billion to implement but prevents 100 million tons of carbon emissions, a $51 metric values the benefit at $5.1 billion—meaning the rule fails the cost-benefit test. At $190 per ton, the same rule generates $19 billion in benefits, easily clearing the threshold.[1]

The metric's power makes it a target for litigation and political friction. The Cato Institute argues that the EPA's updated modeling relies on highly uncertain, centuries-long projections that obscure the immediate economic trade-offs of stringent regulations. Critics contend that embedding a $190 per ton cost into federal rulemaking functions as a shadow carbon tax, bypassing legislative approval by embedding the cost directly into the administrative state.[4]

A central point of contention is whether the metric should measure global damages or only those occurring within U.S. borders. The 2021 Interagency Working Group explicitly directed agencies to account for global damages, arguing that climate change is a transboundary problem and that U.S. emissions cause harm worldwide. Opponents argue that domestic regulatory costs should only be weighed against domestic benefits.[4]

While carbon dioxide dominates the volume of emissions, the social cost framework also applies to more potent greenhouse gases. The 2021 interim estimates placed the social cost of methane at $1,500 per metric ton and nitrous oxide at $18,000 per metric ton, reflecting their significantly higher global warming potential over a 100-year timescale.

The administrative state is now transitioning from the $51 interim figure to the higher EPA estimates in its active rulemaking. The durability of these regulations will depend on how federal courts interpret the agencies' statutory authority to weigh global, centuries-long damages against the immediate compliance costs borne by the domestic energy and transportation sectors.[5]