Last week, a three-judge panel of the federal District Court of Appeals for the D.C. Circuit heard two days of oral arguments in the lawsuit challenging the Environmental Protection Agency’s regulation of greenhouse gas emissions using the Clean Air Act.  The consolidated suit, Coalition for Responsible Regulation vs. EPA, challenges the EPA’s 2009 Endangerment Finding (EF) that greenhouse gas emissions “endanger human health and welfare,” the automobile tailpipe emissions rule, and the “tailoring rule” that exempts smaller stationary emissions sources from being regulated — in contradiction of the explicit language in the 1970 Clean Air Act.

First some background: in April 2007, the U.S. Supreme Court ruled that carbon dioxide, a non-toxic, natural component of the atmosphere — and essential for life on Earth — could be considered an atmospheric pollutant under the Clean Air Act (CAA) of 1970 — and could therefore be regulated by EPA.  But there was an important proviso: the EPA first had to demonstrate that CO2 endangered human health and welfare.  Accordingly, in 2009, the EPA issued an Endangerment Finding (EF), backed up by a Technical Support Document (TSD).  A large number of petitioners then filed lawsuits against the EPA, including the states of Alabama, Texas, and Virginia, disputing the EF.  (My organization, the Science and Environmental Policy Project (SEPP), is one of the petitioners; we concentrate on the scientific validity of the TSD.)

The purpose of the original lawsuit, Commonwealth of Mass. vs EPA, was to force the EPA to regulate CO2 as a pollutant from motor-vehicle tailpipe emissions.  To overcome the problem of “standing,” Mass. presented an affidavit written by the chief scientist of the Environmental Defense Fund, claiming that putative future warming caused by the greenhouse gas CO2 would lead to extensive flooding of New England coastal regions.

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