EPA Endangerment Finding Reconsidered: Science, Law, and the Future of Climate Regulation

The episode examines the rescission of the Obama-era endangerment finding, the legal basis it provided for regulating greenhouse gases under the Clean Air Act, and what this means for future climate regulation. Flora Lichtman speaks with Dr. Andy Miller, an original author on the finding, about its importance for vehicle emissions regulation and the regulatory pathways that remain open even after the ruling is discarded. The discussion also covers the Massachusetts versus EPA Supreme Court decision and how science and law intersect in environmental policy. The conversation closes with Miller’s perspective on the balance between science, law, and the ongoing push to reduce emissions.

Introduction

Science Friday host Flora Lichtman opens a discussion about a significant shift in U.S. climate policy: the rescission of the 2009 endangerment finding. The episode features Dr. Andy Miller, an original author on the finding and a long-time EPA scientist, who provides context on why the finding mattered for greenhouse gas regulation under the Clean Air Act and what its removal could mean for future regulatory action.

"The endangerment finding officially and legally defines greenhouse gasses as air pollutants, and with that definition and that finding, then that means that EPA is obligated to regulate that air pollutant or those air pollutants." - Dr. Andy Miller

What is the Endangerment Finding?

The endangerment finding served as the legal basis for EPA to regulate greenhouse gases as air pollutants, enabling regulatory programs to curb emissions from vehicles and, to a lesser extent, power plants. Miller explains that the finding codified what many believed to be true about climate change and provided a channel for regulation under the Clean Air Act. The episode also highlights how regulatory momentum built on this finding, including vehicle standards, while noting that electric generation sector regulation faced a more modest regulatory push.

"The endangerment finding officially and legally defines greenhouse gasses as air pollutants, and with that definition and that finding, then that means that EPA is obligated to regulate that air pollutant or those air pollutants." - Dr. Andy Miller

The Massachusetts v EPA Context

The conversation revisits Massachusetts v EPA (2007), the Supreme Court decision that greenhouse gases could be regulated under the Clean Air Act, which set the stage for the subsequent endangerment finding. Lichtman and Miller walk through how the Court’s ruling triggered EPA action, and how the finding enabled vehicle emissions regulations that aligned with trends already moving toward cleaner technologies and lower emissions. The discussion places these events within a broader historical arc from Bush to Obama administrations.

It was no surprise, Miller notes, that the finding faced political and legal scrutiny, and the administration changes influenced how aggressively regulatory actions were pursued.

Impacts and Real-World Effects

The immediate impact of the endangerment finding was clear: EPA could regulate greenhouse gases from vehicles under the Clean Air Act, reducing fuel economy and emissions requirements without new congressional legislation. Miller emphasizes that this was a meaningful shift in regulatory authority, particularly as new technologies—electric vehicles, plug-in hybrids, and cleaner generation options—began to mature in the market. While the emissions reductions from power plants followed existing industry trends, the vehicle sector saw a more pronounced regulatory effect, helping to drive technology adoption and efficiency improvements.

"The immediate impact was that it allowed EPA to regulate greenhouse gasses from vehicles." - Dr. Andy Miller

Legal Arguments Behind the Rescission

Lichtman probes the EPA administrator's rationale for rescinding the finding, which she frames as a legal argument rather than a scientific one. The administrator argues that EPA overstepped its authority and that recent Supreme Court decisions require more explicit congressional direction to regulate emissions of this magnitude. The transcript underscores a tension: climate science remains robust, yet the legal framework for regulatory action is contested at the executive level.

"It's a legal argument, at least on its face. It's not based on any scientific evidence" - Flora Lichtman

The Science Perspective

From the scientific community’s viewpoint, climate science has long provided a solid basis for regulatory action. Miller argues that mainstream climate science has been resilient and that the administration’s legal strategy did not hinge on challenging the science itself. Lichtman notes irony in the legal preamble: while acknowledging lingering concerns about the science, the administration chose not to use the science in their legal arguments, signaling a difficult path for those seeking to undermine the scientific consensus in court.

"The climate science is as solid as you're going to get" - Dr. Andy Miller

Outlook: What Comes Next for Regulation

The conversation turns to the practical implications of rescission for regulatory strategy. Even without the endangerment finding, Miller suggests the fossil-fuel industry and auto manufacturers will continue to face regulatory and market pressures from other jurisdictions and technologies. Lichtman stresses that external pressures, including international automakers and the broader move toward cleaner energy, will continue to shape emissions trajectories even in the absence of the endangerment finding. The discussion leaves open the question of whether future Congresses or administrations will restore or replace the legal basis for greenhouse gas regulation, while emphasizing that the science and market dynamics alike will keep pushing toward lower emissions.

"The science wins" - Flora Lichtman