July 29, 2025 update: Administrator Zeldin has unveiled the EPA’s plan to rollback their 2009 Endangerment Finding.

It’s official. U.S. Environmental Protection Agency (EPA) Administrator Lee Zeldin has urged the Trump White House to consider rescinding the Obama administration’s 2009 EPA Endangerment Finding.

The Endangerment Finding greenlit the EPA to regulate six different greenhouse gases—namely carbon dioxide (CO₂) and methane (CH₄)—under the Clean Air Act, relegating them to pollutants that “[…] threaten the public health and welfare of current and future generations.” This determination has since become the cornerstone underpinning burdensome environmental regulations on not only the automotive and energy industries, but also consumers through progressive fuel taxes.

While these regulations might sound like good precautionary measures for our well-being, there are some good reasons why the Trump administration should reconsider this decision almost 16 years later.

Legal background

The 2009 EPA Endangerment Finding was a direct response to the Supreme Court’s April 2, 2007 ruling in Massachusetts v. EPA.

For background, on October 20, 1999, a coalition of 12 states (led by Massachusetts), several cities and environmental organizations petitioned the EPA arguing that they are obligated to regulate greenhouse gas emissions from new motor vehicles under Section 202(a) of the Clean Air Act, which states the EPA Administrator,

“[S]hall by regulation prescribe… standards applicable to the emission of any air pollutant… which in his judgement cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare.”

The Bush EPA denied the petition in 2003, arguing that federal law does not authorize the agency to regulate tailpipe emissions. What’s more, the EPA maintained that even if they had such authority, further investigation would be required to determine whether regulations were justified due to scientific uncertainties and negative socioeconomic implications. Massachusetts appealed the rejection to the Court of Appeals for the D.C. Circuit, and a divided panel ruled in favor of the EPA on July 15, 2005.

After losing in the Circuit Court, the petitioners appealed to the U.S. Supreme Court in 2006. In a 5-4 landmark decision, the Court ruled in favor of Massachusetts on April 2, 2007. They held that greenhouse gases are pollutants under the Clean Air Act, and should the EPA Administrator find that emissions endanger human health, they would be required by law to regulate them. Under President Obama, the EPA did just that in 2009 with their Endangerment Finding.

“The science” is more uncertain than you might think

There is no question that the planet has warmed by about 1.2°C since 1850. There is also no question that CO₂ is a “greenhouse gas” which—all else being equal—should cause the global average surface temperature to rise from emitting more of it into the atmosphere by burning fossil fuels.

However, contrary to what orthodox climate scientists tell you, they cannot say for certain whether most, or even all, of the warming over the last century has been human-caused or not. This is because (a) the natural energy flows in and out of the global climate system have a larger margin of error than the global energy imbalance imposed by human-caused CO₂ emissions, and (b) the models used for future temperature projections are artificially tuned so that CO₂ emissions are the proximate cause of warming. Just as recent warming might be entirely human-caused, it may just as easily be mostly natural and scientists would never know.

Scientists also cannot claim with confidence that global warming—and by extension, CO₂ emissions—are in any meaningful way endangering public health.

First, the human condition has never been better than it is today: Average life expectancy has more than doubled since the 19th century on every inhabited continent; the absolute number of deaths from weather-related disasters have decreased by over 96% since the 1920s despite a six billion-person increase in world population over that time; and crop yields are at all-time record highs. Anyone who claims that we are facing an “existential crisis” is either uninformed or lying.

Secondly, there is no scientific justification to relegate CO₂ to a “pollutant.”

Recall that the EPA classifies CO₂ as pollution because it “[…] contributes to greenhouse gas pollution that threatens public health and welfare.”

Well, by that standard, water vapor should also be classified as a pollutant and regulated because, like CO₂, it is a greenhouse gas. In fact, it is the most abundant and potent in the atmosphere since it (a) comprises 1-4% of atmospheric volume (CO₂ is only 0.04%) and (b) it absorbs a wider spectrum of infrared wavelengths than CO₂.

However, we don’t regulate water vapor because water is an essential compound for life on Earth. But, so is CO₂—it is required for photosynthesis, which forms the basis for the food chain on land and in the oceans.

At the end of the last glacial maximum 20,000 years ago, atmospheric CO₂ levels were on the order of 180 parts per million (ppm). There is plenty of peer-reviewed evidence which suggests that plants were carbon-starved during this period, and had they dropped another 30 ppm, humans might not be here today.

As of last month, the atmospheric CO₂ concentration is 427 ppm. That is about half the level needed for optimum plant growth and only about a third of the concentration in the room you are reading this in. The OSHA Permissible Exposure Limit (PEL) is 5,000 ppm, and submariners are often exposed to concentrations exceeding 10,000 ppm with little to no impact on their mental faculties or ability to complete tasks. At 30,000 ppm, people might have drowsiness or increased blood pressure and only at levels exceeding 40,000 ppm is CO₂ “immediately dangerous to life or health.”

However, we do not have enough fossil fuel reserves left to extract resources from, refine into petroleum products and burn to get the atmospheric concentration anywhere near that ballpark. At concentrations encountered in Earth’s atmosphere, there is no compelling evidence to justify classifying CO₂ as pollution.

It will be legally challenging to overturn

Over the last decade plus, courts have dismissed challenges to rescind the Endangerment Finding, citing the Chevron deference—a legal doctrine established by the Supreme Court in Chevron U.S.A. Inc. v. Natural Resources Defence Council (1984)—which directs courts to defer to a federal agency’s interpretation of ambiguous statutes, which the EPA did with the Endangerment Finding following Massachusetts v. EPA. However, the 40-year-old deference was recently overturned last June in a 6-3 decision with Loper Bright Enterprises v. Raimondo (2024). In a nutshell, bureaucrats can no longer interpret laws and make regulations; it must be done through Congress and reviewed by judicial oversight.

While this sounds like good news for Zeldin, the Supreme Court made it clear in their ruling in Loper Bright Enterprises v. Raimondo that the overturning of the deference does not apply to cases decided under the Chevron framework. Thus, the EPA cannot repeal the Endangerment Finding at the drop of a hat and deregulate greenhouse gas emissions. Any attempt to do so would prove to be futile, as it would be met with legal challenges.

To accomplish this will most likely require the overturning of Massachusetts v. EPA, which means that a new case will need to be brought before the Supreme Court. Then, the Court must revisit their 2007 decision and rule in the Trump administration’s favor. With a conservative majority on the Court, it can be done, but Trump and EPA Administrator Zeldin must make this policy a priority. Knowing how long these legal battles can be drawn out and with the 2028 election cycle approaching in 2028, time is at the essence.

Chris Martz is a senior meteorology major at Millersville University, and a research assistant for the Committee for a Constructive Tomorrow (CFACT).

Chris Martz

Categories: Climate