Today, the Environmental Protection Agency released its long-awaited “Proposed Endangerment and Cause or Contribute Findings for Greenhouse Gases under the Clean Air Act,” as it was directed to do nearly two years ago by the Supreme Court’s decision in Massachusetts v. EPA. The proposed finding contains two key conclusions: first, that the atmospheric concentrations of several key greenhouses gasses (including carbon dioxide, methane and nitrous oxide) threaten the health and welfare of future generations; and second, that the combined emissions of these gasses by new motor vehicles and motor vehicle engines “contribute to the atmospheric concentrations of these key greenhouse gases and hence to the threat of climate change.”

While this is a necessary first step towards any sort of EPA regulation of GHGs under the Clean Air Act, this finding by itself does not guarantee any EPA regulation. As the announcement itself notes, “An endangerment finding under one provision of the Clean Air Act would not by itself automatically trigger regulation under the entire Act.” ClimateIntel has previously covered the issues underlying EPA regulation of greenhouse gasses under the clean air act in our series “Implications Of Regulating CO2 as an NSR Pollutant;” that series can be read here.

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