One year in, President Trump’s climate policy agenda has largely focused on rolling back any progress started by his predecessor—from suspending a rule to limit methane leaks from oil and gas operations on federal land to beginning the process of repealing the Obama Administration’s signature climate change regulation, the Clean Power Plan, and withdrawing from the Paris Agreement. While much of the focus has been on how Congress, states and cities are responding to these actions, the real fight over combating climate change is happening in the courtroom.

Of all the legal challenges, some of the most important center on the Administration’s actions to cast aside the social cost of carbon, a critical tool for evaluating the impacts of greenhouse gas emissions.  This tool provides a consistent, rational, evidence-based approach for setting policy and assessing actions related to climate change, regardless of one’s political beliefs.

How did we get here? Before an administrative agency issues a significant rule or regulation, it is required to analyze whether the benefits of the regulation outweigh its costs. In 2008, the 9th Circuit ruled that the government cannot assume that the costs from climate change are zero when conducting the cost-benefit analysis. An interagency working group, co-led by my University of Chicago colleague Michael Greenstone, formed to create the social cost of carbon metric. Fast forward to 2016, and the courts judged the inter-agency’s approach used to determine the social cost of carbon as reasonable.

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