The Pennsylvania Constitution contains a unique Environmental Rights Amendment (ERA), which recognizes an individual right to “clean air, pure water, and to the preservation of the natural, scenic, historic and esthetic values of the environment.” The ERA also includes a public trust element that makes “Pennsylvania’s public natural resources . . . the common property of all the people, including generations yet to come.” It makes the Commonwealth the “trustee of these resources,” requiring it to “conserve and maintain them for the benefit of all the people.” Recent decisions by the Pennsylvania Supreme Court (the Court) in Robinson Township v. Commonwealth and Pennsylvania Environmental Defense Foundation v. Commonwealth provide significant support for Pennsylvania regulations to address the threat of climate disruption posed by greenhouse gas (GHG) emissions to achieve net zero carbon emissions by the middle of this century.

In light of the threats that climate disruption poses to Pennsylvania’s public natural resources, the text of the ERA, and the principles articulated in those recent cases, we argue that a stable climate (a climate that has not been disrupted by anthropogenic emissions of GHGs) should be considered protected by the rights recognized by the ERA, and the public trust duties it creates. We argue that these rights and duties require Pennsylvania to employ regulatory measures to reduce GHG emissions to the level warranted by the social cost of carbon and to achieve carbon neutrality (net zero emissions) by mid-century. Further, we argue that there are judicially recognizable standards to compel the Commonwealth to exercise its existing authority to limit GHG emissions. In light of existing legislative authority, the obligations imposed by the United Nations Framework Convention on Climate Change, the Paris Agreement, and the federal Clean Air Act, we make the case that this regulatory program should take the form of an economy-wide cap-and-trade program providing for the auction of allowances with a reserve price based on the social cost of carbon and additional measures to prevent leakage and a cap reaching carbon neutrality by mid-century.