Publications

States can benefit from using the social cost of greenhouse gases to aid in making rational policy decisions in a transparent manner. Many states are already using these metrics in their decisionmaking. This report provides information on several issues related to the social cost of greenhouse gases, including discount rates, time horizons, and the global nature of the estimate.

In 2015, the U.S. Environmental Protection Agency (EPA) released the Clean Power Plan, a Clean Air Act rule designed to address the threat of climate change by cutting carbon dioxide emissions from fossil fuel-fired power plants. As part of that rulemaking, the agency prepared an estimate of compliance costs, which it found would be far outweighed by the rule’s climate and health benefits. Since that time, changes in the electric sector have made it even cheaper to meet the rule’s emission targets than EPA anticipated. This report summarizes the findings of EPA’s 2015 Regulatory Impact Analysis; discusses subsequent market and policy developments that have lowered the cost of complying with the Clean Power Plan; and surveys more recent analyses by independent groups, which have estimated substantially lower compliance costs than EPA did.

Despite the Trump administration’s decision to withdraw the official estimate of the Social Cost of Carbon and disband the interagency working group that developed it, a group of prominent economists and lawyers, including several Policy Integrity staff members, have highlighted the metric’s continued validity for policymaking in recent letter published in the journal Science.

Given the vast uncertainty surrounding climate impacts, meta-analyses of global climate damage estimates are a key tool for determining the relationship between temperature and climate damages. Due to limited data availability, previous meta-analyses of global climate damages potentially suffered from multiple sources of coefficient and standard error bias. To address and test for these biases, we expand on previous datasets to obtain sufficient degrees of freedom to make the necessary model adjustments, including dropping duplicate estimates and including methodological variables. Estimating the relationship between temperature and climate damages using weighted least squares with cluster-robust standard errors, we find strong evidence that duplicate and omitted variable biases flatten the relationship. However, the magnitude of the bias greatly depends on the treatment of speculative high-temperature (>4 ◦C) damage estimates. Replacing the DICE-2013R damage function with our preferred estimate of the temperature–damage relationship, we find a three- to four-fold increase in the 2015 SCC relative to DICE, depending on the treatment of productivity. When catastrophic impacts are also factored in, the SCC increases by four- to five-fold.

To solve the unprecedented global commons problem posed by climate change, all nations must internalize the global externalities of their emissions. If not, collective efforts will never achieve an efficient, stable climate outcome. The United States’ practice of looking at the global impact of emissions has come under attack in courtrooms and academic journals, with some arguing that the U.S. should instead consider only the domestic impacts of climate change in its decisionmaking.

In a letter published in Review of Environmental Economics and Policy, we argue that federal agencies should continue to use a global number for Social Cost of Carbon, as developed by the Interagency Working Group on Social Cost of Carbon. First, the United States benefits tremendously if other countries set policy based on global rather than local effects. From a legal perspective, not only does international law—the U.N. Framework Convention on Climate Change—commit the United States to account for global effects, but domestic laws like the Clean Air Act and the National Environmental Policy Act also either require or give discretion to agencies to consider global climate costs. Many seemingly “foreign” climate damages would actually spill over to harm the United States.