On February 12, 2026, the U.S. Environmental Protection Agency (EPA) issued a final rule rescinding the 2009 Greenhouse Gas Endangerment Finding and eliminating all federal greenhouse gas (GHG) emission standards for U.S. motor vehicles and engines. To justify this action, EPA has adopted an interpretation of the Clean Air Act that has no judicial support – arguing that it lacks authority to regulate GHG emissions under section 202(a)(1) because it does not have explicit congressional authorization to address global climate change concerns. In addition, EPA asserts that there is no basis for the 2009 endangerment finding or subsequent regulations because, in its view, GHG emissions standards for U.S. motor vehicles and engines do not have a “material” effect on public health and welfare.
In this blog post, we focus on EPA’s arguments about the non-material or “de minimis” effects of U.S. motor vehicle emissions. As detailed below, EPA has made a scientific and factual determination about harm attribution – a reversal from its 2009 endangerment finding – which it has improperly characterized as a legal determination and failed to substantiate with scientific evidence. Moreover, EPA is relying on a “drop in the bucket” argument about climate-related harms that is both legally and factually unsound, especially when applied to a source category that generates nearly 4% of total global CO2 emissions and causes approximately $415 billion in annual climate damages, based on EPA’s 2023 social cost of carbon (SC-CO2) estimates. EPA’s approach to the harm attribution question is clearly inconsistent with its statutory directives, and its factual conclusions are contradicted by a large body of scientific evidence that the agency has simply ignored.
Background
Section 202(a)(1) of the Clean Air Act requires EPA to develop emission standards for the control of air pollution from new motor vehicles or engines which may reasonably be anticipated to endanger public health or welfare. EPA and the courts have consistently interpreted this provision as requiring a purely scientific judgment about the effects of motor vehicle emissions on people and the environment. (See, e.g., Massachusetts v. EPA, Coalition for Responsible Regulation v. EPA.) The statute does not authorize EPA to consider other factors, such as regulatory costs or feasibility, when issuing an endangerment finding. Rather, the statute directs EPA to consider the effect of emission control standards at a later stage in the rulemaking – specifically, if EPA issues an affirmative endangerment finding, it must promulgate standards “which reflect the greatest degree of emission reduction achievable” through available technologies, taking into account considerations such as cost, energy, and safety. See section 202(a)(3)(A).
In Massachusetts v. EPA, the Supreme Court held that GHG emissions qualified as “air pollutants” under section 202(a)(1) and that EPA could not avoid making a scientific determination on endangerment based on political or regulatory considerations not articulated in the statute. In 2009, EPA issued an affirmative endangerment finding for GHG emissions from U.S. motor vehicles that was supported by a detailed scientific analysis of the relationship between GHG emissions, global climate change, and potential effects on public health and welfare. As discussed in a previous blog post, the 2009 endangerment finding was upheld in court, with the D.C. Circuit finding that EPA had amassed a “substantial” body of evidence to support the finding. The underlying scientific evidence has only grown stronger over time.
Nonetheless, in the proposed rule for this action, EPA sought to justify the repeal of the endangerment finding on scientific grounds. EPA argued that there was “insufficient reliable information” about the harmful effects of climate change, and that reports from scientific authorities such as the Intergovernmental Panel on Climate Change (IPCC) and U.S. Global Change Research Program (USGCRP) were “unduly pessimistic” about those harmful effects. However, EPA backtracked from this position in the final rule – it claims that the repeal is based purely on legal considerations, and that it is not issuing a new finding under section 202(a)(1).
EPA’s primary argument is that it lacks “clear congressional authorization” for regulating GHG emissions under section 202(a), and its regulatory authority only extends to “air pollution” that threatens health and welfare “through local and regional exposure.” EPA cites recent Supreme Court decisions applying the “major questions” doctrine as its primary support for this argument. As we explained in comments on the proposed rule, EPA’s interpretation is clearly inconsistent with legal precedent: the Supreme Court held in Massachusetts v. EPA that GHGs “unambiguous[ly]” qualify as “air pollutants” under section 202(a), and thus “EPA has statutory authority to regulate emission of such gases from new motor vehicles.” The Supreme Court has also consistently affirmed EPA’s authority to regulate GHG emissions under the Act, even where it has found that EPA’s choice of regulatory mechanism exceeded its statutory authority. (See, e.g., West Virginia v. EPA, Utility Air Regulatory Group v. EPA). EPA now argues that GHG emissions do not cause “air pollution” within the meaning of the Act, even though they qualify as “air pollutants.” But the Act expressly links these concepts, defining “air pollutant” as “any air pollution agent or combination of such agents.” 42 U.S.C. § 7602(g).
EPA has also articulated a “separate but complementary basis” for the repeal – specifically, that GHG emission standards for new motor vehicles and engines are “futile because they have no material (i.e., non-de minimis) impact on global climate change concerns.” EPA argues that even the complete elimination of GHG emissions from U.S. motor vehicles would not have a material effect on public health and welfare. EPA claims that this is not a scientific finding on endangerment, but rather a legal determination related to the scope of its statutory authority which precludes it from fully assessing the question of endangerment. In particular, EPA asserts that it “should not and need not make an endangerment finding” when subsequent regulations “would have no meaningful impact on the identified dangers.”
Because EPA treats this as a purely “legal” analysis, EPA concludes that it is “unnecessary and inappropriate to resolve outstanding scientific questions” related to 2009 Endangerment Finding. Accordingly, EPA treats all of the scientific information that was submitted during the notice and comment period as irrelevant to the final rule. For example, EPA claims that scientific materials submitted by the National Academies of Sciences, Engineering, and Medicine (“National Academies”) – which are directly relevant to assessing attributable harms from GHG emissions, as well as the efficacy of emission control measures – are “not pertinent” to the final action, because EPA’s decision is “a matter of statutory interpretation, not scientific analysis within the [National Academies’] purview.”
But EPA has clearly made a factual determination about the magnitude of harms attributable to U.S. motor vehicle emissions which runs directly counter to the scientific analysis underpinning the 2009 endangerment finding. EPA characterizes this as a legal determination in order to avoid meeting its evidentiary burden under section 202(a)(1).
EPA’s Analysis of Attributable Climate Effects from U.S. Motor Vehicles
In the final rule, EPA predicts that annual CO2 emissions from U.S. motor vehicles will comprise approximately 4% of global CO2 emissions in 2027, 3% of global CO2 emissions in 2050 and 10% of global CO2 emissions in 2100. This is based on EPA’s projections of annual emissions from all new and existing on-road motor vehicles (1,630 million tons CO2 in 2027, 1,390 million tons CO2 in 2050, and 1,380 million tons CO2 in 2100) as compared with projected global emissions in the IPCC’s “shared socioeconomic pathway 2” (SSP2-4.5).
EPA claims that even the complete elimination of these U.S. motor vehicle emissions would not have a material effect on predicted trends in global mean surface temperature (GMST) or global mean sea level rise (GSLR). Specifically, EPA projects that U.S. motor vehicle emissions will contribute approximately 2% of the increase in GMST by 2050 (~ 0.013°C) and 3% of the increase in GMST by 2100 (~ 0.037°C), and approximately 1% of the increase in GSLR by 2050 (~ 0.09 cm) and 2% of the increase in GSLR by 2100 (~ 1.4 cm). EPA concludes that these contributions to global trends in temperature and sea level rise are “relatively minor” without any further assessment of the attributable effects on public health and welfare.
EPA asserts that this scenario is a “dramatic overestimation” of the potential impacts of GHG emission standards “which apply only to new vehicles and engines.” EPA therefore considers a separate scenario where modeled impacts are discounted by 50% and estimates that maintaining GHG emissions standards for U.S. motor vehicles would result in a 0.007°C impact on projected GMST through 2050 and a 0.019°C impact on GMST through 2100, and a 0.05 cm impact on projected GSLR through 2050 and a 0.7 cm impact on GSLR through 2100.” In this part of its analysis, EPA fails to acknowledge that the vast majority of existing vehicles on the road in 2050 and 2100 would have been subject to the GHG standards for model years 2012 and later, and the tightening of these emissions standards would result in further emission reductions in future years.
EPA concludes that the impacts on public health and welfare are “de minimis” (i.e., “no material impact”) under both the complete elimination and 50 percent reduction scenarios. EPA says it did not consider other impacts identified in the 2009 endangerment finding – e.g., hurricanes, floods, heat waves, and ocean acidification – due to the “speculative, multi-faceted, and multi-causal” nature of those impacts. EPA also asserts that the “projected impacts on GMST and GSLR trends do not translate directly to adverse health and welfare impacts.”
Problems with EPA’s Determination Regarding the “De Minimis” Effect of Motor Vehicle Emissions
There are several major problems with EPA’s assessment of the public health and welfare effects attributable to U.S. motor vehicle GHG emissions. First, EPA has issued a factual determination on endangerment – essentially reversing course from its 2009 endangerment finding – without providing an adequate scientific justification for the reversal. Second, EPA’s “drop in the bucket” argument is logically incoherent and inconsistent with legal precedent and scientific understanding of climate change. Third, regarding the factual determination itself: there is no scientific basis for concluding that U.S. motor vehicle emissions have a “de minimis” effect on climate-related harms. To the contrary, the available scientific evidence shows that these emissions have a significant effect on public health and welfare by any reasonable measure.
- No Scientific Justification for Reversing Course on 2009 Endangerment Finding
EPA’s factual determination that U.S. motor vehicle emissions have “de minimis” impacts on public health runs directly counter to the scientific conclusions underpinning the 2009 endangerment finding and subsequent endangerment findings for other source categories. EPA has an obligation to provide a reasoned explanation this reversal in accordance with sections 202(a) and 307(d) of the Clean Air Act. EPA has circumvented that obligation by framing its decision as a matter of “statutory interpretation” and insisting that it is not issuing a new endangerment finding under Section 202(a)(1). EPA insists that it is “unnecessary and inappropriate to resolve outstanding scientific questions regarding global climate change concerns” in the context of this action, and thus it performed only a cursory analysis of GHG emissions and their effect on GMST and GSLR which was solely intended to support its argument about regulatory futility. As noted above, EPA did not consider any scientific evidence regarding the actual impacts attributable to the projected increases in GMST or GSLR.
In addition, EPA’s novel theory of regulatory “futility” collapses the distinction between an endangerment finding and the subsequent assessment of regulatory feasibility and efficacy, essentially guaranteeing that EPA will consider factors other than the effect of emissions on public health and welfare when issuing findings under section 202(a)(1). This theory also inverts the logical order of assessment, i.e., EPA claims that it must first determine whether regulations would have a “meaningful impact on the identified dangers” before it conducts a full scientific analysis to identify those dangers. This is inconsistent with the text and structure of section 202(a)(1), which requires EPA to promulgate emission standards for any air pollutants from motor vehicles that may reasonably be anticipated to endanger public health or welfare (thus requiring an initial finding regarding the overall effects of emissions, not the effects of regulatory action). See Massachusetts v. EPA. Moreover, the statute does not authorize EPA to avoid issuing motor vehicle emission standards – or to rescind existing standards – based on EPA’s conclusions about the degree of emissions limitation achievable through those standards.
EPA’s justification is a prime example of the long-extant “drop in the bucket” argument against climate action, i.e., the notion that individual actions or policies are too small to have a meaningful effect on global climate change. This argument is an inversion of reality. As the IPCC and USGCRP have both recognized, climate change is a cumulative problem and every incremental increase in GHG emissions and global temperatures will further exacerbate the adverse impacts on people and ecosystems. Accordingly, every incremental measure taken to reduce GHG emissions will help mitigate the adverse effects on public health and welfare.
The Supreme Court recognized this in Massachusetts v. EPA, where it held that U.S. motor-vehicle emissions make a “meaningful contribution” to global climate change “judged by any standard” and that even incremental mitigation measures can help offset the injuries attributable to those emissions. Granted, the Supreme Court was evaluating injury, causation, and redressability for Article 3 standing purposes, and the specific threshold for cognizable harm may be different when considering EPA’s statutory duties under section 202(a). But the Supreme Court’s commentary is nonetheless relevant when considering the general merits of the “drop in the bucket” argument. In addition, the D.C. Circuit found that EPA had adequately supported its 2009 finding that motor vehicle emission “cause or contribute” to climate-related harms in Coalition for Responsible Regulation v. EPA, and the Supreme Court denied cert on that issue, thus allowing the D.C. Circuit’s holding to stand.
There are many other examples of courts and legal authorities rejecting the “drop in the bucket” argument with regards to government action on climate change. These include major decisions from the International Court of Justice (ICJ), the European Court of Human Rights (ECtHR), the Inter-American Court of Human Rights (IACtHR), and national high courts in Germany, the Netherlands, Nepal, India, Colombia, and elsewhere. For example, the ICJ Advisory Opinion on the Obligations of States in Respect to Climate Change recognized that all countries have a duty of care with regards to the control of GHG emissions, as the “risks and projected adverse impacts and related loss and damage from climate change will escalate with every increment of global warming.” Similarly, the ECtHR has recognized that “every incremental increase in emissions” causes an increase in health-related risks, and “the fact that climate change [is] caused by cumulative, global emissions [does] not absolve individual States from responsibility” for climate-related harms attributable to their GHG emissions.
One notable aspect of these legal decisions is that they recognize government obligations to control GHGs even where the emissions at issue are much smaller than those attributable to U.S. motor vehicles. This is generally true for cases involving national obligations because the vast majority of countries emit less CO2 from all sectors than U.S. motor vehicles (the only exceptions are China, Russia, India and the U.S. itself). There are also U.S. decisions recognizing legally cognizable harms at much smaller scales. For example, the Supreme Court of Montana rejected the “drop in the bucket” argument in Held v. Montana, finding that there was a sufficient causal connection between 32 million tons of CO2 attributable to Montana fossil fuels and climate-related harms to human health and welfare.
Thus, EPA’s position is inconsistent with scientific evidence and out of step with the weight of the world’s legal opinion. It would also lead to absurd consequences if adopted by other regulatory entities. Based on EPA’s logic, there is essentially no sector or source category in the entire world that makes a “material” contribution to climate change (since the same logic could be applied to other major source categories in the U.S. as well as top emitters like China, India, and Russia).
- EPA’s Conclusion About the De Minimis Impact on Public Health and Welfare
The third problem with EPA’s assessment relates to the factual conclusion itself. By EPA’s own estimate, U.S. on-road motor vehicles will generate 1,630 million tons of CO2 in 2027 – roughly 4% of total global emissions. This is an exceedingly large contribution to global emissions. As noted above, this is larger than the total CO2 emissions attributable to all but four countries – the U.S., China, India, and Russia. It is equivalent to approximately half of the emissions attributable to the entire European Union, and it exceeds the emissions generated by the entire continent of Africa. It is patently absurd to argue that this qualifies as a “de minimis” contribution to climate-related harms.
The IPCC, USGCRP, National Academies, and many other scientific authorities have recognized that climate change is a global problem with widespread, pervasive, and potentially irreversible adverse effects on public health and welfare. The overall magnitude of harms attributable to climate change is enormous, and it is clear that a 4% contribution to these harms surpasses any reasonable threshold of materiality.
EPA attempts to minimize the impacts by focusing on attributable increases in global mean temperature (GMST) and sea level rise (GSLR) which have the appearance of being relatively minor (e.g., the emissions will “only” a 0.013°C increase in GMST by 2050 and a 0.037°C increase in GMST by 2100). By focusing on these seemingly small changes in long-term average trends, EPA is obscuring the actual effect of these changes on human health and well-being.
The significance of a 0.037°C in global mean temperature becomes more obvious when considering the specific impacts that will occur as a result of that increase. For example, using a quantification framework developed by Abram et al. (2025), the attributable increase in GMST would result in: (i) approximately 48.5 million additional people exposed to unprecedented extreme heat; (ii) approximately 33.4 million additional people left outside of the human climate niche, and (iii) the death of an additional ~ 1.5 billion coral colonies in the Great Barrier Reef during every future mass bleaching event. EPA’s SC-CO2 estimates provide additional insights on the potential magnitude of harm. Based on EPA’s 2023 SC-CO2 estimates (2% average discount rate) and 2027 emission projections (1,630 million tons CO2), U.S. on-road motor vehicles will cause approximately $415 billion in annual climate damages next year.
There are many other tools that can be used to assess the effects attributable to GHG emissions from U.S motor vehicles, including impact attribution research, health impact assessments, end-to-end attribution studies, and other frameworks for estimating economic damages. See, e.g., Romanello et al. (2025), Callahan & Mankin (2025), Howard et al. (2025), Berberian et al. (2024), Burke et al. (2023). EPA received comments from the Sabin Center and many other organizations detailing the available scientific information on climate change and how this should inform EPA’s assessment of public health and welfare effects (see, e.g., this report submitted by the National Academies). Unfortunately, because EPA has framed this as a purely legal determination, it has simply refused to engage with the scientific evidence on this topic.
Conclusion
EPA has made a sweeping determination that GHG emissions from U.S. motor vehicles do not materially affect public health and welfare. EPA has characterized this as a matter of “statutory interpretation” to avoid the evidentiary requirements for an endangerment finding under section 202(a)(1). The agency’s own projections show that U.S. motor vehicles account for a substantial share of global emissions, and the scientific literature makes clear that even small incremental increases in global temperature translate to significant impacts on people and ecosystems. EPA has totally failed to engage with the scientific evidence on climate impacts and instead has invoked a novel and unsupported legal theory of “futility” in order to circumvent its regulatory obligations under the Clean Air Act.
Jessica Wentz
Jessica is now a non-resident senior fellow at the Sabin Center.
