Science Friday - EPA Rescinds The Legal Basis For Regulating Greenhouse Gases

Episode Date: February 26, 2026

On February 12, the Environmental Protection Agency dealt a major blow to the government’s power to fight climate change by rescinding a key piece of research called the endangerment finding. The finding, issued in 2009, basically says: Greenhouse gas emissions endanger public health and welfare—and because they’re harmful, they must be regulated. It's the legal basis for the federal government’s regulation of greenhouse gases under the Clean Air Act. So what does it mean that this finding has been thrown out? Host Flora Lichtman digs into this question with Andy Miller, an original author on the endangerment finding who spent more than 30 years working for the EPA. Guest: Dr. Andy Miller worked on air pollution and climate change at the EPA for more than 30 years. He was an original author on Endangerment Finding. Transcripts for each episode are available within 1-3 days at sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Hey, it's Flora Lichten, and you're listening to Science Friday. Earlier this month, the Trump administration dealt a major blow to the government's power to fight climate change by rescinding a key piece of research. This is a big deal. This is EPA head Lee Zeldin talking about it. Referred to by some as the holy grail of federal regulatory overreach. The 2009 Obama EPA endangerment finding is now eliminated. The endangerment finding. It's the legal basis for the federal government's regulation of greenhouse gases under the Clean Air Act. And it basically says greenhouse gas emissions endanger public health and welfare. And because they're harmful, they must be regulated. So what does it mean that this finding has been thrown out? Joining me now is an original author on the endangerment finding, Dr. Andy Miller. He was at the EPA for more than 30 years working on air pollution and climate change. Andy, welcome to Science Friday. Thank you, Flora, and thank you for having me on.

I think the endangerment finding might be new to people, this term. How big of a deal is this in the climate world? Well, it's huge. It officially and legally defines greenhouse gases as air pollutants. And with that definition and that finding, then that means that EPA, is obligated to regulate that air pollutants or those air pollutants under the Clean Air Act. It is the basis for the regulatory programs. So it's a big deal from an EPA perspective. You were an original author on the finding. This must be personal for you.

What was your response to the news that it had been rescinded? It was no surprise. We could see this coming from November of 2024. They've long wanted to get rid of the endangerment finding. They'd really like to get rid of the Massachusetts versus EPA Supreme Court decision. So this is not something that came as a surprise. Certainly a disappointment, but not a shock. What was that Massachusetts decision?

So that's when the state of Massachusetts, sued EPA saying that greenhouse gases were air pollutants as defined by the Clean Air Act. And so EPA at that time, this was, I believe 2007 under George Bush, disagreed. So Massachusetts sued EPA. And it went to the Supreme Court. And Supreme Court at that time in 2007 said, yes, the requirements of the Clean Air Act are such that greenhouse gases fit the definition of an air pollutant for EPA, and EPA must then respond. So that's what triggered the endangerment finding?

Yes. So there was the Massachusetts versus EPA decision. Then EPA had to take the steps to show that, yes, it is an air pollutant, or that greenhouse gases are air pollutants under the Clean Air Act, and therefore are subject to regulation. And without that endangerment finding, then EPA could not move forward with any kind of regulatory program. Will you take me behind the scenes a little bit? I mean, what was it like back around 2007, 2008, 2009? Was it controversial to get the endangerment finding codified? Well, actually, it was.

internally, you know, at the working level where I was at, it was another scientific evaluation. And it wasn't that far off from the kinds of things that we normally did. It went through all of the internal evaluations, the reviews, the management on up to the administrator's office. And the administrator, Stephen Johnson, under George Bush, actually sent this over to the Office of Management and Budget as per the process. And OMB decided they just were not going to open the email. This was very late in the Bush administration. They just decided they weren't going to open the email. That was the strategy. Let's just ignore it. Let's not even open

it. Yeah. And so it came up again, obviously, when Obama came into office. And in 2009, then it had completed the whole legal process to become promulgated as an EPA rule. And what was the impact of it? Well, the immediate impact was that it allowed EPA to regulate greenhouse gases from vehicles. And so EPA did not have to wait for Congress to say, new fuel efficiency standards. EPA was able to use the endangerment finding to set these rules for new vehicles. And so that was the big deal. Now, EPA also tried to use this as the basis for reducing emissions from electric generating stations, from power plants. That was not hugely

ambitious. It didn't require deep cuts. It really codified what was already happening in the utility industry. The emissions were starting to go down already as we moved from coal to natural gas, bringing in more renewables. So the impact there was considerably less. But on the vehicle side, it was substantial, but it was also following a trend that was already underway. As new technologies came into the market, as we get more and more electric vehicles, more and more plug-in hybrids. So, you know, you can argue it either way. I think that we're better off with it by far.

I don't think it's yet a catastrophe. And I think to throw it out. To throw it out, exactly. Because it's not going to stop legal challenges from the states. So it's not clear right now whether the fossil fuel industry is going to have to face 50 different regulatory schemes or not. And even the automobile industry, they're still going to be facing. pressure from international car makers. Right.

I mean, and it's not like consumers want to buy cars that use a lot of gas, you know? Most of them know. That's right. And this is one of the reasons why I don't think that this is a catastrophe, is that a lot of these pressures from overseas are still going to be present here and still going to drive efficiency and reduced emissions, even if there is not the regular. driver. What is the argument that EPA administrator Lee Zeldon is giving for rescinding the finding? Is it a science argument or something different? It's a legal argument, at least on its

face. It's not based on any scientific evidence, only on legal considerations. And those legal considerations are really focused on their view that EPA overstepped its bounds, that given the recent Supreme Court decisions that EPA could not make decisions of this magnitude without specific congressional direction. I mean, it's kind of interesting that the EPA isn't challenging the science, because, of course we hear from President Trump that, you know, climate scientists are stupid and CO2 is never a pollutant. We've heard that from this administration. What do you make of that?

From a scientific perspective, that's the big story, that EPA was really forced to accept in this legal setting that the mainstream climate science is valid. They were not able to show that the science is either an error or is too uncertain to be used. used as the basis for regulatory decisions. And so it's kind of, funny is not quite the word, but somewhat ironic that when you read the current preamble, the legal preamble to the actual rule, they say over and over again that they still think there are problems with the science. But then they turn right around and say, well, we are not using this science in our legal arguments.

And so in some ways, they're apologizing for not using the science that they developed. Right. They really wanted to show, they wanted to take that to the Supreme Court and have the Supreme Court bless their view of the science that said it was wrong or that it was too uncertain to be used because that would then validate all of the arguments that, I won't even say all the people in industry, but certainly people who are against the EPA's regulatory actions, that they wanted to see that really moved out. And they were not able to do that. I mean, you've been working in climate science for 30 years. Does that seem like progress to you?

Oh, absolutely. It doesn't surprise any, really, any of the climate science community. We've always known that the climate science is as solid as you're going to get. But what it does is it says it makes it that much harder for institutions, for agencies to make the claim that the climate science is flawed and flawed to an extent that it cannot be used in a legal proceedings. Because what EPA has done here has said, we can't use, we can't show that the science is wrong or that the science is flawed. And so this was their shot. This was their opportunity to make that case. And they couldn't do it. And so not being able to make that case tells everybody else that really, from a legal

perspective, that argument should be over. You're retired now, but you were at the EPA for more than 30 years. What are you hearing from your colleagues within the agency about this? Everybody's really disappointed. It really makes no sense. sooner or later we're going to have to regulate or we're certainly going to have to reduce emissions. Whether we do that through regulatory means or other means is unclear. But we're moving in this direction.

And no matter what the law is, no matter what the ideology is, no matter what the economics are, at the end of the day, the science wins. And there's no way around that. Dr. Andy Miller was a scientist at the EPA for more than 30 years and an original author on the Endangerment Finding. Andy, thanks for joining me today. Thank you, Flora. It was a pleasure to be here. This episode was produced by Rasha Aredi. We'll catch you tomorrow. I'm Flor Lichten.