Proposed Rule2025-14572
Reconsideration of 2009 Endangerment Finding and Greenhouse Gas Vehicle Standards
Primary source
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Published
August 1, 2025
Issuing agencies
Environmental Protection Agency
Abstract
In this action, the U.S. Environmental Protection Agency (EPA) is proposing to repeal all greenhouse gas (GHG) emission standards for light-duty, medium-duty, and heavy-duty vehicles and engines to effectuate the best reading of Clean Air Act (CAA) section 202(a). We propose that CAA section 202(a) does not authorize the EPA to prescribe emission standards to address global climate change concerns and, on that basis, propose to rescind the Administrator's prior findings in 2009 that GHG emissions from new motor vehicles and engines contribute to air pollution which may endanger public health or welfare. We further propose, in the alternative, to rescind the Administrator's prior findings in 2009 because the EPA unreasonably analyzed the scientific record and because developments cast significant doubt on the reliability of the findings. Lastly, we propose to repeal all GHG emission standards on the alternative bases that no requisite technology for vehicle and engine emission control can address the global climate change concerns identified in the findings without risking greater harms to public health and welfare.
Full Text
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[Federal Register Volume 90, Number 146 (Friday, August 1, 2025)]
[Proposed Rules]
[Pages 36288-36365]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-14572]
[[Page 36287]]
Vol. 90
Friday,
No. 146
August 1, 2025
Part II
Environmental Protection Agency
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40 CFR Parts 85, 86, 600, et al.
Reconsideration of 2009 Endangerment Finding and Greenhouse Gas Vehicle
Standards; Proposed Rule
Federal Register / Vol. 90 , No. 146 / Friday, August 1, 2025 /
Proposed Rules
[[Page 36288]]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 85, 86, 600, 1036, 1037, and 1039
[EPA-HQ-OAR-2025-0194; FRL-12715-01-OAR]
RIN 2060-AW71
Reconsideration of 2009 Endangerment Finding and Greenhouse Gas
Vehicle Standards
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: In this action, the U.S. Environmental Protection Agency (EPA)
is proposing to repeal all greenhouse gas (GHG) emission standards for
light-duty, medium-duty, and heavy-duty vehicles and engines to
effectuate the best reading of Clean Air Act (CAA) section 202(a). We
propose that CAA section 202(a) does not authorize the EPA to prescribe
emission standards to address global climate change concerns and, on
that basis, propose to rescind the Administrator's prior findings in
2009 that GHG emissions from new motor vehicles and engines contribute
to air pollution which may endanger public health or welfare. We
further propose, in the alternative, to rescind the Administrator's
prior findings in 2009 because the EPA unreasonably analyzed the
scientific record and because developments cast significant doubt on
the reliability of the findings. Lastly, we propose to repeal all GHG
emission standards on the alternative bases that no requisite
technology for vehicle and engine emission control can address the
global climate change concerns identified in the findings without
risking greater harms to public health and welfare.
DATES:
Comments. Comments must be received on or before September 15,
2025. Comments on the information collection provisions submitted to
the Office of Management and Budget (OMB) under the Paperwork Reduction
Act (PRA) are best assured of consideration by OMB if OMB receives a
copy of your comments on or before September 2, 2025.
Public Hearing. The EPA will announce information regarding the
public hearing for this proposal in a supplemental Federal Register
document. Please refer to the SUPPLEMENTARY INFORMATION section for
additional information on the public hearing.
ADDRESSES: Comments. You may send comments, identified by Docket ID No.
EPA-HQ-OAR-2025-0194, by any of the following methods:
<bullet> Federal eRulemaking Portal: <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>
(our preferred method). Follow the online instructions for submitting
comments.
<bullet> Email: <a href="/cdn-cgi/l/email-protection#b8d995d9d6dc95ca95fcd7dbd3ddccf8ddc8d996dfd7ce"><span class="__cf_email__" data-cfemail="c1a0eca0afa5ecb3ec85aea2aaa4b581a4b1a0efa6aeb7">[email protected]</span></a>. Include Docket ID No. EPA-
HQ-OAR-2025-0194 in the subject line of the message.
<bullet> Mail: U.S. Environmental Protection Agency, EPA Docket
Center, OAR Docket, Mail Code 28221T, 1200 Pennsylvania Avenue NW,
Washington, DC 20460.
<bullet> Hand Delivery or Courier: EPA Docket Center, WJC West
Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004.
The Docket Center's hours of operations are 8:30 a.m.-4:30 p.m.,
Monday-Friday (except Federal Holidays).
Instructions. All submissions received must include the Docket ID
No. for this rulemaking. Comments received may be posted without change
to <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>, including any personal information
provided. For detailed instructions on sending comments and additional
information on the rulemaking process, see the ``Public Participation''
heading of the SUPPLEMENTARY INFORMATION section of this document.
FOR FURTHER INFORMATION CONTACT: Alan Stout, Assessment and Standards
Division, Office of Transportation and Air Quality, Environmental
Protection Agency, 2000 Traverwood Drive, Ann Arbor, MI 48105;
telephone number: (734) 214-4805; email address: <a href="/cdn-cgi/l/email-protection#b9cacdd6cccd97d8d5d8d7f9dcc9d897ded6cf"><span class="__cf_email__" data-cfemail="6c1f18031918420d000d022c091c0d420b031a">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION:
A. Public Participation
Written Comments. Submit your comments, identified by Docket ID No.
EPA-HQ-OAR-2025-0194, at <a href="https://www.regulations.gov">https://www.regulations.gov</a> (our preferred
method), or the other methods identified in the ADDRESSES section. Once
submitted, comments cannot be edited or removed from the docket. The
EPA may publish any comment received to its public docket. Do not
submit to the EPA's docket at <a href="https://www.regulations.gov">https://www.regulations.gov</a> any
information you consider to be Confidential Business Information (CBI),
Proprietary Business Information (PBI), or other information whose
disclosure is restricted by statute. If you choose to submit CBI or PBI
as a comment to the EPA's docket, please send those materials to the
person listed in the FOR FURTHER INFORMATION CONTACT section.
Multimedia submissions (audio, video, etc.) must be accompanied by a
written comment. The written comment is considered an official comment
and should include discussion of all points you wish to make. The EPA
will generally not consider comments or comment contents located
outside of the primary submission (i.e., on the web, cloud, or other
file sharing system). Please visit <a href="https://www.epa.gov/dockets/commenting-epa-dockets">https://www.epa.gov/dockets/commenting-epa-dockets</a> for additional submission methods; the full EPA
public comment policy; information about CBI, PBI, or multimedia
submissions; and general guidance on making effective comments.
To facilitate comment on the portions of the rule on which the EPA
is specifically soliciting comment, the EPA has indexed each comment
solicitation with a unique identifier (e.g., ``C-1'', ``C-2'') in
section VII of this preamble to provide a consistent framework for
effective and efficient provision of comments. Accordingly, we ask that
commenters include the corresponding identifier when providing comments
relevant to that comment solicitation. We ask that commenters include
the identifier either in a heading or within the text of each comment,
to make clear which comment solicitation is being addressed. We note
that we are not limiting comment to these identified areas.
Participation in Virtual Public Hearing. The EPA will announce
information regarding the public hearing for this proposal in a
supplemental document in the Federal Register. The hearing notice,
registration information, and any updates to the hearing schedule will
also be available at <a href="https://www.epa.gov/regulations-emissions-vehicles-and-engines/proposed-rule-reconsideration-2009-endangerment-finding">https://www.epa.gov/regulations-emissions-vehicles-and-engines/proposed-rule-reconsideration-2009-endangerment-finding</a>. Please refer to this website for any updates regarding the
hearings. The EPA does not intend to publish additional documents in
the Federal Register announcing updates to the hearing schedule.
Docket. All documents in the docket are listed on the
<a href="http://www.regulations.gov">www.regulations.gov</a> website. Although listed in the index, some
information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, is not placed on the internet and will be
publicly available only in hard copy form through the EPA Docket Center
at the location listed in the ADDRESSES section of this document.
[[Page 36289]]
B. Action Applicability
This action relates to companies that manufacture, sell, or import
into the United States light-, medium-, or heavy-duty motor vehicles
and engines. Potentially affected categories and entities include the
following:
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NAICS code \a\ NAICS title
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336110........................ Automobile and Light-duty Motor Vehicle
Manufacturing.
336120........................ Heavy Duty Truck Manufacturing.
336211........................ Motor Vehicle Body Manufacturing.
336213........................ Motor Home Manufacturing.
336310........................ Motor Vehicle Gasoline Engine and Engine
Parts Manufacturing.
336390........................ Other Motor Vehicle Parts Manufacturing.
333618........................ Other Engine Equipment Manufacturing.
423110........................ Automobile and Other Motor Vehicle
Merchant Wholesalers.
811198........................ All Other Automotive Repair and
Maintenance.
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\a\ NAICS Association. NAICS & SIC Identification Tools. Available
online: <a href="https://www.naics.com/search">https://www.naics.com/search</a>.
This table is not intended to be exhaustive but rather provides a
guide for readers regarding entities potentially affected by this
action. This table lists the types of entities that the EPA is
presently aware could potentially be affected by this action. Other
types of entities not listed in the table could also be affected. To
determine whether your entity is regulated by this action, you should
carefully examine the applicability criteria found in Code of Federal
Regulations (CFR) title 40, parts 85, 86, 600, 1036, and 1037. If you
have questions regarding the applicability of this action to a
particular entity, consult the person listed in the FOR FURTHER
INFORMATION CONTACT section.
Table of Contents
I. Executive Summary
A. Introduction
B. Need for Regulatory Action
C. Summary of the Major Provisions in This Proposed Action
II. Background
A. The EPA's Historical Approach to CAA Section 202(a)
B. Petitions for Rulemaking and Massachusetts v. EPA
C. The 2009 Endangerment Finding
D. Implementation of the 2009 Endangerment Finding
E. Reconsideration of the 2009 Endangerment Finding
III. Legal Framework for Proposed Action
A. Proposed Rescission of Endangerment Finding
B. Proposed Amendments to New Motor Vehicle and Engine
Regulations
IV. Proposed Rescission of the Endangerment Finding
A. Primary Rationale for Proposed Rescission
1. Best Reading of CAA Section 202(a)
2. Lack of Clear Congressional Authorization
B. Alternative Rationale for Proposed Rescission
1. Climate Science Discussion
2. Proposed Conclusions
V. Separate Bases for Proposed Repeal of GHG Emission Standards
A. There Is No Requisite Technology for Light- and Medium-Duty
Vehicles That Meaningfully Addresses the Identified Dangers of the
Six ``Well-Mixed'' GHGs
B. There Is No Requisite Technology for Heavy-Duty Vehicles That
Addresses the Identified Dangers of the Six ``Well-Mixed'' GHGs
C. Eliminating GHG Emissions From All Motor Vehicles Would Be
Futile
D. More Expensive New Vehicles Prevent Americans From Purchasing
New Vehicles That Are More Efficient, Safer, and Emit Fewer GHGs
VI. Proposed Repeal of GHG Emission Standards
A. Scope and Impacts of Proposed Repeal
B. Light- and Medium-Duty Vehicle GHG Program
1. Background on the Light- and Medium-Duty Vehicle GHG Program
2. Proposed Changes to the Light- and Medium-Duty Vehicle GHG
Regulations
C. Heavy-Duty Engine and Vehicle GHG Program
1. Background on the Heavy-Duty Engine and Vehicle GHG Program
2. Proposed Changes to the Heavy-Duty Engine and Vehicle GHG
Regulations
VII. Requests for Comment
VIII. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 14094: Modernizing Regulatory Review
B. Executive Order 14192: Unleashing Prosperity Through
Deregulation
C. Paperwork Reduction Act (PRA)
1. Light- and Medium-Duty Vehicle--2024 Final Rule
2. Heavy-Duty Vehicle GHG Phase 3--2024 Final Rule
3. Nonroad Compression-Ignition Engines and On-Highway Heavy
Duty Engines, Supporting Statement for Information Collection
Request (March 2023 Revision)
D. Regulatory Flexibility Act (RFA)
E. Unfunded Mandates Reform Act (UMRA)
F. Executive Order 13132: Federalism
G. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
H. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
I. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
J. National Technology Transfer and Advancement Act (NTTAA) and
1 CFR Part 51
I. Executive Summary
A. Introduction
In this action, the EPA proposes to rescind all greenhouse gas
(GHG) emission standards for light-duty, medium-duty, and heavy-duty
vehicles and engines under CAA section 202(a). Upon review of the
underlying actions and intervening legal and scientific developments,
including recent decisions by the U.S. Supreme Court and the scientific
information summarized in this preamble, the EPA no longer believes
that we have the statutory authority and record basis required to
maintain this novel and transformative regulatory program. We seek
comment on all aspects of this proposal, including on the legal and
scientific developments that are being subject to public comment for
the first time in this rulemaking.
In 2009, the EPA took the unprecedented step of asserting authority
to regulate GHG emissions in a standalone action titled ``Endangerment
and Cause or Contribute Finding for Greenhouse Gases Under Section
202(a) of the Clean Air Act,'' 74 FR 66496 (Dec. 15, 2009)
(Endangerment Finding). In that action, we interpreted CAA section
202(a) for the first time to authorize regulation of domestic emissions
from new motor vehicles and engines based on global climate change
concerns rather than air pollution that endangers public health or
welfare through local or regional exposure. 74 FR 66526-27. We also
asserted that because the statute is ``silent on [the] issue,'' CAA
section 202(a) grants ``procedural discretion'' to issue standalone
findings that trigger a duty to regulate without considering the
standards that must issue in response.
[[Page 36290]]
74 FR 66501-02. The Administrator exercised this newfound discretion to
make separate findings that elevated global concentrations in the upper
atmosphere of six ``well-mixed GHGs''--carbon dioxide (CO<INF>2</INF>),
methane, nitrous oxide (N<INF>2</INF>O), hydrofluorocarbons (HFCs),
perfluorocarbons (PFCs), and sulfur hexafluoride (SF<INF>6</INF>)--
constitute ``air pollution'' that may reasonably be anticipated to
endanger public health and welfare, 74 FR 66516-36, and that GHG
emissions from all potential classes of motor vehicles and engines
contribute to such elevated global concentrations of GHGs in the upper
atmosphere and therefore to air pollution that endangers public health
and welfare, 74 FR 66536-45.
With respect to endangerment, the Administrator found that global
concentrations of GHGs from all foreign and domestic sources
``constitute the largest anthropogenic driver of climate change'' and
attributed climate change impacts to global GHG concentrations. 74 FR
66517. Next, the Administrator summarized literature reviews finding
that climate change ``can increase the risk of morbidity and
mortality'' indirectly through increased global temperature, air
quality effects, and changes in extreme weather events and can impact
welfare indirectly through net impacts on food production, forestry,
water resources, sea level rise, energy infrastructure, and ecosystems.
74 FR 66522-35. On that basis, the Administrator found that global
concentrations of GHGs constitute ``air pollution'' that endangers
public health and welfare. 74 FR 66516. For purposes of this preamble,
we use the phrase global climate change concerns to refer to the risks
the Administrator associated with climate change in 2009.
With respect to causation or contribution, the Administrator used
emissions data for existing motor vehicles and engines to project that
all potential classes of new motor vehicles and engines would emit four
GHGs--CO<INF>2</INF>, methane, N<INF>2</INF>O, and HFCs--that would
collectively amount to 4.3 percent of global GHG emissions. 74 FR
66543. The Administrator acknowledged that more would usually be
required to support contribution ``when addressing a more typical local
or regional air pollution problem.'' 74 FR 66539. Nevertheless,
asserting discretion to interpret the ambiguous term ``contribute,''
the Administrator found that the ``unique'' nature of global climate
change meant that ``contributors must do their part even if their
contributions to the global climate change problem, measured in terms
of percentage, are smaller than typically encountered when tackling
solely regional or local environmental issues.'' 74 FR 66542-43.
The EPA subsequently relied on the Endangerment Finding to impose
increasingly stringent GHG emission standards for new motor vehicles
and engines and to attempt, largely without success, to extend its GHG
initiative into additional CAA programs. In Utility Air Regulatory
Group v. EPA, 573 U.S. 302 (2014) (UARG), the Supreme Court rejected
our attempt to extend GHG emission standards to stationary sources
subject to Title I and Title V requirements, including after we
admitted that applying the statutory scheme as written to GHG emissions
from most covered stationary sources would be unworkable. And in West
Virginia v. EPA, 597 U.S. 697 (2022), the Court vacated our attempt to
shift the power grid away from using fossil fuels through GHG standards
for existing power plants under CAA section 111(d). The Court held in
both cases that the agency actions at issue implicated the major
questions doctrine, and that Congress must clearly authorize agencies
to take actions that decide major questions of policy. Nevertheless,
the EPA continued to retain and expand GHG emission standards for new
motor vehicles and engines that impose billions of dollars in
compliance costs on American businesses and consumers. Meanwhile,
global GHG concentrations in the upper atmosphere have continued to
rise, driven primarily by increased emissions from foreign sources,\1\
all without producing the degree of adverse impacts to public health
and welfare in the United States that the EPA anticipated in the 2009
Endangerment Finding.
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\1\ Crippa, M. et al. (2023). GHG emissions of all world
countries. Publications Office of the European Union: <a href="https://doi.org/10.2760/953322">https://doi.org/10.2760/953322</a>.
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The EPA now proposes to rescind the Endangerment Finding and all
resulting GHG emission standards for new motor vehicles and engines,
including the light-duty, medium-duty, and heavy-duty vehicle and
engine standards for model years (MY) 2012 to 2027 and beyond. The
remainder of this section describes the need for regulatory action and
the scope of the proposed action, including rescission of the
Endangerment Finding, repeal of related GHG emission standards, and
minor conforming adjustments to unrelated emission standards for new
motor vehicles and engines that we are not proposing to alter as part
of this rulemaking.
Section II of this preamble sets out relevant background, including
the events leading up to the Endangerment Finding, the approach taken
in the Endangerment Finding to analyzing the scientific record, and the
regulations issued since 2009 in reliance on the Endangerment Finding.
We also summarize the premises, assumptions, and conclusions in the
Endangerment Finding and the scientific information, including
empirical data, peer-reviewed studies, and real-world developments
since 2009 that led the Administrator to develop concerns sufficient to
initiate reconsideration of the ongoing validity and reliability of the
Endangerment Finding.
Section III of this preamble describes our legal authority to
rescind the Endangerment Finding and repeal the resulting GHG standards
issued under CAA section 202(a). Because this proposed action would not
impact fuel economy standards and emission standards for criteria
pollutants and hazardous air pollutants regulated under the CAA, we
explain the relationship between these regulations to set the outer
bounds of amendments at issue in this rulemaking.
Section IV.A of this preamble describes our proposal to rescind
these prior actions because the Endangerment Finding exceeded our
statutory authority under CAA section 202(a). As explained further
below, we propose that the term ``air pollution'' as used in CAA
section 202(a) is best read in context as referring to local or
regional exposure to dangerous air pollution, consistent with our
longstanding practice before 2009. We further propose that CAA section
202(a) does not grant the Administrator ``procedural discretion'' to
issue standalone findings that trigger a duty to regulate, or,
conversely, to prescribe standards, without making the requisite
findings for the particular air pollutant emissions and class or
classes of new motor vehicles or engines at issue. We also propose that
CAA section 202(a) does not authorize the Administrator to make
separate findings for endangerment and causation or contribution.
Rather, we propose that CAA section 202(a) requires the Administrator
to find that the relevant air pollutant emissions from the class or
classes of new motor vehicles or engines at issue cause, or contribute
to, air pollution which endangers public health or welfare, without
relying on emissions from stationary or other sources regulated by
distinct CAA provisions. As the Supreme Court made clear in Loper
Bright Enterprises v. Raimondo, 603 U.S. 369 (2024), we can no longer
rely on statutory silence or ambiguity to expand our regulatory power.
And
[[Page 36291]]
because the Nation's response to global climate change concerns is an
issue of significant importance that Congress did not clearly address
in CAA section 202(a), we propose that the major questions doctrine
further reinforces and provides an additional basis for our proposed
interpretations and actions. The Agency did not have the benefit of the
Court's decisions in Loper Bright and West Virginia, among other
applicable precedents, when issuing the Endangerment Finding in 2009.
Finally, we explain that the EPA reached contrary conclusions in the
Endangerment Finding by misconstruing the Supreme Court's decision in
Massachusetts v. EPA, 549 U.S. 497 (2007), which vacated our denial of
a petition for rulemaking on distinct grounds. Read on its own terms,
Massachusetts did not require the Agency to find that GHGs are subject
to regulation under CAA section 202(a) and does not support our
implementation of the statute since 2009.
Section IV.B of this preamble describes our alternative proposal to
rescind these prior actions even if CAA section 202(a) authorizes the
EPA to address GHG emissions based on global climate change concerns by
concluding that the Administrator exercised that authority unreasonably
in the Endangerment Finding. Specifically, we propose that the EPA
misapplied the statutory standard for regulation to the scientific
record by severing the analysis into separate parts without considering
whether all parts of the analysis, taken as a whole, supported the
findings and regulatory determinations required by the statute. We
further propose that empirical data, peer-reviewed studies, and real-
world developments since 2009 have cast significant doubt on many of
the critical premises, assumptions, and conclusions in the Endangerment
Finding such that it would be unreasonable to retain the decision and
the resulting regulatory framework. In proposing this alternative, we
note that the Supreme Court has continued to emphasize that agencies
have significant discretion when making complex judgments within the
bounds of an authorizing statute.\2\ We propose that the Administrator
may now exercise the discretion expressly delegated to him by Congress
in the text of CAA section 202(a) by rescinding the Endangerment
Finding.
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\2\ Seven Cnty. Infrastructure Coal. v. Eagle Cnty., 145 S. Ct.
1497, 1511-15 (2025); FDA v. Wages & White Lion Invs., L.L.C., 145
S. Ct. 898, 917 (2025); Baltimore Gas & Elec. Co. v. NRDC, Inc., 462
U.S. 87, 103 (1983); see also Huntsman Petrochemical LLC v. EPA, 114
F.4th 727, 735 (D.C. Cir. 2024) (``In the case of EPA's evaluation
of scientific data within its area of expertise, [courts] accord an
extreme degree of deference.'' (quotation marks omitted)).
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Section V of this preamble proposes additional bases for repealing
the EPA's GHG emission standards for new motor vehicles and engines
under CAA section 202(a) even if the Endangerment Finding were to
remain in place. We propose that there is no ``requisite technology''
responsive to the global climate change concerns identified in the
Endangerment Finding given evidence that reducing GHG emissions from
new motor vehicles and engines to zero would not have a scientifically
measurable impact on global GHG concentrations and climate trends. We
also propose that, on balance, and contrary to the core objectives of
CAA section 202(a), GHG emission standards harm public health and
welfare by increasing prices, decreasing consumer choice, and slowing
the replacement of older vehicles that are less safe and emit a greater
volume and variety of air pollutants than new motor vehicles and
engines.
Section VI of this preamble details the scope of the proposed
repeal, including its relationship to distinct regulatory programs and
federal preemption, the revisions to 40 CFR parts 85, 86, 600, 1036,
1037, and 1039 required to effectuate repeal of all GHG emission
standards, and conforming adjustments to regulatory provisions that we
are not proposing to reopen or substantively revise. Specifically, in
this NPRM we are not proposing to change at this time elements of the
regulations that are necessary for programs unrelated to the
Endangerment Finding, including emission standards for criteria
pollutants and air hazards and the EPA's statutory role in vehicle
standards administered by the National Highway Traffic Safety
Administration (NHTSA).
Section VII of this preamble specifically requests comment on key
aspects of this proposed action and indexes comment solicitation to
promote public participation and facilitate our review of public
comments. Note that we are not limiting public participation to the
issues raised in this section and will respond to all comments within
the scope of this proposal. Rather, we are highlighting aspects of the
proposal for which public input would be particularly helpful in
determining whether and in what respects to finalize this proposed
action.
B. Need for Regulatory Action
Immediately upon taking office, President Trump established new
Executive Branch priorities for energy, transportation, and consumer
choice and committed to ensuring regulations remain within
constitutional and statutory bounds. On January 20, 2025, the President
issued an Executive Order titled ``Unleashing American Energy'' to
address the burdens placed by unnecessary regulations on energy
affordability, job creation, and national security.\3\ As relevant
here, the President directed the EPA Administrator to submit
recommendations to the Director of OMB on the legality and continuing
applicability of the 2009 Endangerment Finding.\4\ On February 19,
2025, the President issued an Executive Order titled ``Ensuring Lawful
Governance and Implementing the President's `Department of Government
Efficiency' Deregulatory Initiative'' that further instructed agencies,
including the EPA, to review existing regulations for consistency with
the Constitution and the best reading of the authorizing statute.\5\
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\3\ Executive Order 14154, 90 FR 8353 (Jan. 29, 2025).
\4\ Id. Sec. 6(f).
\5\ Executive Order 14219, 90 FR 10583 (Feb. 25, 2025).
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Upon confirmation by the Senate, Administrator Lee Zeldin committed
the EPA to prioritizing its core statutory mission and ensuring that
all regulatory actions are clearly grounded in statutory authority and
the best reading of the law. As part of these efforts, and consistent
with the ``Unleashing American Energy'' Executive Order, the
Administrator initiated a review of the legality and applicability of
the Endangerment Finding. On February 19, 2025, the Administrator
submitted a memorandum to the OMB Director recommending that the EPA
reconsider the Endangerment Finding to address legal and scientific
developments that appear to undermine the bases for that action and
subsequent regulations.\6\ The Administrator noted that recent Supreme
Court decisions, including Loper Bright, West Virginia, UARG, and
Michigan v. EPA, 576 U.S. 743 (2015), provided new guidance on how we
should interpret and apply the statutes Congress entrusted us to
administer.\7\ The Administrator further noted that the Endangerment
Finding recognized significant uncertainties in its conclusions and
assumptions that should be evaluated in light of more recent empirical
data and scientific
[[Page 36292]]
evidence.\8\ Accordingly, the Administrator announced on March 12,
2025, that the EPA would reconsider the Endangerment Finding and
subsequent actions to determine whether our GHG regulations have an
adequate statutory basis and to seek public input on developments since
2009.\9\
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\6\ Memorandum from Lee Zeldin, Administrator, Environmental
Protection Agency, to Russell Vought, Director, Office of Management
and Budget (Feb. 19, 2025) (Feb. 19, 2025 Memo), available in the
docket for this rulemaking.
\7\ Id. at 1.
\8\ Id. at 8.
\9\ ``Trump EPA Kicks Off Formal Reconsideration of Endangerment
Finding with Agency Partners'' (Mar. 12, 2025), available at <a href="https://www.epa.gov/newsreleases/trump-epa-kicks-formal-reconsideration-endangerment-finding-agency-partners">https://www.epa.gov/newsreleases/trump-epa-kicks-formal-reconsideration-endangerment-finding-agency-partners</a>.
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As part of this reconsideration, the EPA closely examined
applicable law, including judicial precedents and interpretive aids
bearing on the meaning of CAA section 202(a) and related statutory
provisions. We also reviewed actions taken to regulate GHG emissions
from new motor vehicles and new motor vehicle engines since 2009,
assessed the costs and non-cost adverse impacts of these GHG emission
standards, and evaluated the effectiveness of these GHG emission
standards in reducing the dangers identified in the Endangerment
Finding, that is, in mitigating the impacts anticipated to result from
elevated global GHG concentrations in the upper atmosphere.
Furthermore, the Administrator reviewed available information,
including the most recently available science, bearing on the
assumptions and conclusions in the Endangerment Finding, the impacts of
global GHG concentrations on public health and welfare in the United
States, and the relative contribution of domestic emissions from new
motor vehicles and engines to global GHG concentrations. As part of
that review, the Administrator received and evaluated the draft report
submitted by the U.S. Department of Energy (DOE) Climate Working Group
(CWG) to Secretary of Energy Christopher Wright on May 27, 2025, titled
``Impacts of Carbon Dioxide Emissions on the U.S. Climate'' (2025 CWG
Draft Report). The 2025 CWG Draft Report analyzes empirical data, peer-
reviewed studies, and available scientific information bearing on
direct human influence on ecosystems and climate, climate response to
CO<INF>2</INF> emissions, and impacts on ecosystems and society.\10\
The Administrator also considered available assessments by the U.S.
Government and relevant international bodies, including the Third,
Fourth, and Fifth National Climate Assessments (NCAs) reported by the
U.S. Global Change Research Program (USGCRP) \11\ and the Fifth
Assessment Report (AR5) and Sixth Assessment Report (AR6) by the United
Nations Intergovernmental Panel on Climate Change (IPCC).\12\ As
discussed in section IV.B of this preamble, the Administrator also
considered critiques of the NCAs, and the Fifth NCA in particular, and
reviewed these analyses for consistency with OMB information quality
guidelines \13\ and the transparency and reliability requirements of
Executive Order 14303, ``Restoring Gold Standard Science.'' \14\
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\10\ The 2025 CWG Draft Report was provided to the EPA on May
27, 2025, and was reviewed and relied upon in formulating this
proposal. The EPA understands that DOE is releasing an updated
version of the CWG draft report and seeking public comment on the
updated report, which includes additional information and
typographical corrections that the EPA did not rely upon in
formulating this proposal. Interested parties may review and comment
on the updated version of the CWG draft report for consideration as
part of DOE's efforts through the docket available at <a href="https://www.energy.gov/topics/climate">https://www.energy.gov/topics/climate</a>.
\11\ Created by the Global Change Research Act of 1990, Public
Law 101-606, 104 Stat. 3096, the USGCRP reports an NCA at least
every four years to Congress and the President that must (1)
integrate, evaluate, and interpret the findings of the Program and
discuss the scientific uncertainties with such findings; (2) analyze
the effects of global change on the natural environment,
agriculture, energy production and use, land and water resources,
human health and welfare, human social systems, and biological
diversity; and (3) analyze current trends in global change, both
human-induced and natural, and project major trends for the
subsequent 25 to 100 years. See 15 U.S.C. 2936.
\12\ The IPCC invites participation by members of the United
Nations and World Meteorological Organization and summarizes
available literature on climate science but does not conduct its own
research. See United Nations Intergovernmental Panel on Climate
Change, About the IPCC, available online at <a href="https://www.ipcc.ch/about/">https://www.ipcc.ch/about/</a>.
\13\ ``Guidelines for Ensuring and Maximizing the Quality,
Objectivity, Utility, and Integrity of Information Disseminated by
Federal Agencies; Republication,'' 67 FR 8452 (Feb. 22, 2002).
\14\ 90 FR 22601 (May 29, 2025).
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The Administrator's review of the relevant information, including
scientific literature, gave rise to serious concerns that our actions
taken to regulate GHG emissions from new motor vehicles and engines
exceed our statutory authority under CAA section 202(a) and are
otherwise inappropriate. Continuing to impose billions of dollars in
regulatory costs on American businesses and consumers without an
adequate legal basis would threaten to undermine public confidence in
our activities and commitment to fulfilling the Agency's core mission:
protecting human health and the environment. The EPA has expended
significant resources implementing the GHG regulatory program for
mobile sources and attempting to expand its GHG regulatory program to
stationary sources with limited success in the courts and no apparent
real-world results, often at the expense of programs that fall squarely
within our statutory authority. Prompt action is needed to address
these concerns with the benefit of public participation.
Relatedly, the Administrator has serious concerns that many of the
scientific underpinnings of the Endangerment Finding are materially
weaker than previously believed and contradicted by empirical data,
peer-reviewed studies, and scientific developments since 2009. This
proposal seeks public comment on these developments for the first time.
Prompt action is needed to address these concerns, and the
Administrator requests stakeholder input on the continuing vitality of
the assumptions, predictions, and conclusions animating the
Endangerment Finding.
C. Summary of the Major Provisions in This Proposed Action
If finalized, this action would rescind the 2009 Endangerment
Finding for GHGs emitted by new motor vehicles and new motor vehicle
engines under CAA section 202(a) (74 FR 66496). If finalized, this
action would also rescind denials of petitions for reconsideration of
the Endangerment Finding in 2022 and 2010 entitled ``Endangerment and
Cause or Contribute Findings for Greenhouse Gases Under Section 202(a)
of the Clean Air Act; Final Action on Petitions,'' 87 FR 25412 (Apr.
29, 2022), and ``EPA's Denial of the Petitions to Reconsider the
Endangerment and Cause or Contribute Finding for Greenhouse Gases Under
Section 202(a) of the Clean Air Act,'' 75 FR 49556 (Aug. 13, 2010).\15\
Although the 2022 and 2010 petition denials have no prospective legal
effect, we propose to rescind them for the sake of consistency and to
ameliorate potential confusion regarding the EPA's proposed action. As
explained later in this preamble, the denials reflect many of the same
legal and scientific flaws we propose to correct by rescinding the
Endangerment Finding. We seek comment on the impact of the denials, if
any, and on whether the denials were legally flawed for additional
reasons not explicitly explored in this proposal. In addition, as a
result of these proposed changes, we would no longer have a basis for
issuing or retaining GHG emission standards for new motor vehicles and
new motor vehicle engines, including
[[Page 36293]]
for MYs that have completed manufacture but are subject to ongoing
obligations. As discussed elsewhere in this preamble, the EPA is
reconsidering additional endangerment findings and GHG emission
standards issued under distinct provisions of the CAA in separate
rulemakings and is not reopening or proposing to modify those
additional findings and standards in this proceeding.
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\15\ The 2022 petition denials included a notice of decision in
the Federal Register (87 FR 25412), brief letters communicating the
denials to the petitioners, and a decision document entitled ``EPA's
Denial of Petitions Relating to the Endangerment and Cause or
Contribute Findings for Greenhouse Gases Under Section 202(a) of the
Clean Air Act'' (Apr. 21, 2022) (2022 Denial), available online at
<a href="https://www.epa.gov/system/files/documents/2022-04/decision_document.pdf">https://www.epa.gov/system/files/documents/2022-04/decision_document.pdf</a>.
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In connection with the proposed rescission of the Endangerment
Finding, if finalized, this action would remove all existing
regulations that require new motor vehicle and new motor vehicle engine
manufacturers to measure, report, or comply with GHG emission
standards. Specifically, the EPA proposes to remove regulations in 40
CFR parts 85, 86, 600, 1036, and 1037 pertaining to the control of GHG
emissions from light-, medium-, and heavy-duty vehicles and engines,
including emission standards, test procedures, averaging, banking, and
trading requirements (ABT), reporting requirements, and fleet-average
emission requirements.\16\ As a result of these proposed changes, motor
vehicle and engine manufacturers would no longer have future or current
obligations for the measurement, control, or reporting of GHG emissions
for any vehicle or engine, including for previously manufactured MYs.
However, we are not proposing to reopen or modify any regulations
necessary for criteria pollutant and air toxic measurement and
standards, Corporate Average Fuel Economy (CAFE) testing, and
associated fuel economy labeling requirements. We seek comment on
whether any elements of the regulations, test procedures, or GHG
emission models that are proposed for removal should remain to support
programs unrelated to the GHG emission standards and why the
preservation of such an element is necessary to support the unrelated
program or programs.
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\16\ ``Light-Duty Vehicle Greenhouse Gas Emission Standards and
Corporate Average Fuel Economy Standards,'' 75 FR 25324 (May 7,
2010); ``Greenhouse Gas Emissions Standards and Fuel Efficiency
Standards for Medium- and Heavy-Duty Engines and Vehicles,'' 76 FR
57106 (Sept. 15, 2011); ``2017 and Later Model Year Light-Duty
Vehicle Greenhouse Gas Emissions and Corporate Average Fuel Economy
Standards,'' 77 FR 62624 (Oct. 15, 2012); ``Greenhouse Gas Emissions
and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and
Vehicles-Phase 2,'' 81 FR 73478 (Oct. 25, 2016); ``The Safer
Affordable Fuel-Efficient (SAFE) Vehicles Rule for Model Years 2021-
2026 Passenger Cars and Light Trucks,'' 85 FR 24174 (Apr. 30, 2020);
``Revised 2023 and Later Model Year Light-Duty Vehicle Greenhouse
Gas Emissions Standards,'' 86 FR 74434 (Dec. 30, 2021); ``Multi-
Pollutant Emissions Standards for Model Years 2027 and Later Light-
Duty and Medium-Duty Vehicles,'' 89 FR 27842 (Apr. 18, 2024);
``Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles-Phase
3,'' 89 FR 29440 (Apr. 22, 2024).
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II. Background
A. The EPA's Historical Approach to CAA Section 202(a)
Congress originally enacted the language that became CAA section
202(a) as part of the Motor Vehicle Pollution Control Act of 1965,
which required the Secretary of Health, Education, and Welfare to
``prescribe . . . standards, applicable to the emission of any kind of
substance, from any class or classes of new motor vehicles or new motor
vehicle engines, which in his judgment cause or contribute to, or are
likely to cause or contribute to, air pollution which endangers the
health or welfare of any persons.'' \17\ Congress retained this
language, while adding additional requirements for the content of
emission standards, in the Air Quality Act of 1967,\18\ and, later,
incorporated it into the Clean Air Act of 1970, which transferred the
Secretary's regulatory authority to the newly created EPA.\19\
Separately, the 1970 CAA addressed emissions from existing vehicles and
engines, stationary sources, and aircraft engines.\20\ As subsequently
amended, CAA section 202(a) has remained a critical part of the
comprehensive national framework for regulating air pollution from
mobile sources, and new motor vehicles and new motor vehicle engines in
particular, under Title II of the CAA.\21\
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\17\ Public Law 89-272, 202(a), 79 Stat. 992, 992-93 (1965).
\18\ Public Law 90-148, 202(a), 81 Stat. 485, 499 (1967).
\19\ Public Law 91-604, 84 Stat. 1690 (1970).
\20\ Id.
\21\ In the Clean Air Act Amendments of 1977, Congress replaced
the phrase ``which endangers the public health or welfare'' with
``which may reasonably be anticipated to endanger public health or
welfare.'' Public Law 95-95, 401(d)(1), 91 Stat. 685, 791 (1977).
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In its first four decades administering the statute, the EPA
applied CAA section 202(a) to local and regional air pollution problems
through rulemakings that prescribed standards and set forth the
Administrator's findings that the relevant air pollutant emissions
cause, or contribute to, air pollution which may reasonably be
anticipated to endanger public health or welfare.\22\ As explained in
the following subsections, the EPA maintained this approach through
2008 and never sought to invoke CAA section 202(a) to regulate in
response to global climate change concerns.
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\22\ See 74 FR 66501, 66527, 66538, 66543 (acknowledging this
regulatory history).
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B. Petitions for Rulemaking and Massachusetts v. EPA
In October 1999, a coalition of 19 environmental organizations
petitioned the EPA to regulate the emission of four GHGs--
CO<INF>2</INF>, methane, N<INF>2</INF>O, and HFCs--from new motor
vehicles and engines under CAA section 202(a)(1). Petitioners claimed
that these four GHGs were ``air pollutant[s]'' under CAA section
302(g), significantly contributed to global climate change, and met the
statutory standard for regulation under CAA section 202(a)(1). Thus,
petitioners claimed that the EPA had the authority and obligation to
find that GHG emissions from new motor vehicles and engines cause, or
contribute to, air pollution which may reasonably be anticipated to
endanger public health or welfare and to prescribe standards in
response.
In September 2003, after receiving and responding to nearly 50,000
public comments on the relevant issues, the EPA denied the 1999
petitions in a final action titled ``Control of Emissions from New
Highway Vehicles and Engines,'' 68 FR 52922 (Sept. 8, 2003) (2003
Denial). The 2003 Denial asserted three primary reasons for denying the
petitions. First, after ``examin[ing] the fundamental issue of whether
the CAA authorizes the imposition of control requirements'' to ``reduce
the risk of global climate change,'' we concluded that ``CO<INF>2</INF>
and other GHGs cannot be considered `air pollutants' subject to the
CAA's regulatory provisions for any contribution they may make to
global climate change.'' 68 FR 52925. Citing the Supreme Court's
decision in FDA v. Brown & Williamson Tobacco Corp., 529 U.S. 120
(2000), we noted that the CAA does not address GHGs as a regulatory
matter, including in recent amendments, and that ``EPA has used these
provisions to address air pollution problems that occur primarily at
ground level or near the surface of the earth.'' 68 FR 52926. On this
basis, we concluded that GHGs ``are not air pollutants under the CAA's
regulatory provisions, including sections 108, 109, 111, 112, and 202''
because they categorically are not ``air pollutant[s]'' under the Act-
wide definition in CAA section 302(g). 68 FR 52928. Second, we
concluded that regulating GHG emissions from motor vehicles and engines
under the CAA would interfere with NHTSA's separate authority to
implement fuel economy standards. 68 FR 52929. Finally, we asserted
that regulating GHG emissions from motor vehicle engines under the CAA
would
[[Page 36294]]
undermine the President's overall policy approach of addressing global
climate change through voluntary actions and incentives, the promotion
of further research and technologies, and international negotiations.
68 FR 52930-31.
In Massachusetts, the Supreme Court narrowly reversed the D.C.
Circuit's decision to uphold the EPA's denial of the 1999 petitions for
rulemaking.\23\ The Court took particular issue with the EPA's reading
of the Act-wide definition in CAA section 302(g), ruling that ``[t]he
Clean Air Act's sweeping definition of `air pollutant' . . . embraces
all airborne compounds of whatever stripe'' and provided no textual
basis for excluding CO<INF>2</INF> or the three other GHGs raised in
the petitions for rulemaking. 549 U.S. at 528-29. The Court also
addressed EPA's reliance on Brown & Williamson, which the majority
construed as having found no congressional intent to ban the sale of
tobacco products outright because such an application of the relevant
statute would have been highly unlikely and because the Food and Drug
Administration (FDA) had expressly refused to assert such authority in
the past. Id. at 530-31. In contrast, in Massachusetts, the Court found
that the CAA did not reflect a congressional intent to categorically
exclude GHGs and, citing several Agency memoranda, that we had not
similarly foresworn all authority to regulate GHGs as a categorical
matter. Id. Notably, the Court expressly declined to decide whether the
EPA was required to issue an affirmative endangerment finding as to GHG
emissions under the standard set out in CAA section 202(a). Id. at 534
(``We need not and do not reach the question whether on remand EPA must
make an endangerment finding.''). Nor did the Court address ``whether
policy concerns can inform EPA's actions in the event that it makes
such a finding.'' Id. at 534-35. Rather, the Court held that we must
respond to the petitions by deciding whether GHG emissions from new
motor vehicles and engines meet the standard for regulation in CAA
section 202(a) or whether the science was too uncertain to make any
determination, and that, in doing so, we must ``ground [our] reasons
for action or inaction in the statute.'' Id. at 535.\24\
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\23\ The D.C. Circuit majority had upheld the denial on the
merits because ``the EPA Administrator properly exercised his
discretion under Sec. 202(a)(1) in denying the petition for
rulemaking.'' Massachusetts v. EPA, 415 F.3d 50, 58 (D.C. Cir.
2005). The dissent argued that CAA section 202(a)'s breadth provided
the EPA sufficient authority to regulate GHGs, that more specific
authorization was not required, and that the EPA's policy
justifications were inadequate reasons to deny the petitions. Id. at
67-82 (Tatel, J., dissenting).
\24\ Writing for four members of the Court, Chief Justice
Roberts would have dismissed the petitions for review for lack of
Article III standing. 549 U.S. at 535 (Roberts, C.J., joined by
Scalia, Thomas, and Alito, J.J., dissenting). Writing for the same
four members of the Court, Justice Scalia would have denied the
petitions on the grounds that the Administrator reasonably exercised
judgment in declining to regulate and that CAA section 302(g)'s
definition of ``air pollutant'' does not clearly encompass
CO<INF>2</INF> and other GHGs that naturally occur in the ambient
air. 549 U.S. at 549 (Scalia, J., joined by Roberts, C.J., and
Thomas and Alito, J.J., dissenting).
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C. The 2009 Endangerment Finding
The EPA responded to the Supreme Court's decision in Massachusetts
by issuing an advanced notice of proposed rulemaking titled
``Regulating Greenhouse Gas Emissions Under the Clean Air Act,'' 73 FR
44354 (July 30, 2008) (2008 ANPRM). The Administrator began by noting
it was ``clear that if EPA were to regulate [GHG] emissions from motor
vehicles under the Clean Air Act,'' the interplay between CAA section
202(a) and similarly worded statutory provisions ``could result in an
unprecedented expansion of EPA authority that would have a profound
effect on virtually every sector of the economy and touch every
household in the land.'' 73 FR 44355. The Administrator cautioned that
because the CAA was ``originally enacted to control regional pollutants
that cause direct health effects,'' invoking authority to regulate GHG
emissions ``would inevitably result in a very complicated, time-
consuming, and, likely, convoluted set of regulations'' that ``would be
relatively ineffective at reducing [GHG] concentrations'' and have a
``potentially damaging effect on jobs and the U.S. economy.'' Id.
The 2008 ANPRM echoed the Administrator's concerns by seeking
public comment on invoking CAA section 202(a) to regulate new motor
vehicle and engine emissions in response to global climate change
concerns. We acknowledged that the CAA ``was not specifically designed
to address GHGs,'' 73 FR 44397, and that the EPA had historically
interpreted and applied its CAA regulatory authorities to address local
and regional air pollution, 73 FR 44408. We further noted that Congress
was considering legislation to address the Nation's response to global
climate change concerns and that, since Massachusetts, Congress had
passed and the President had signed into law the Energy Independence
and Security Act (EISA), which amended provisions applicable to the
EPA's Renewable Fuels Standard (RFS) program and NHTSA's CAFE standards
program. 73 FR 44398. Finally, we noted that the EPA had received
additional petitions to regulate stationary sources and additional
GHGs, including water vapor, all of which suggested that GHG emission
regulations could not readily be limited to new motor vehicles and
engines. 73 FR 44399 & n.26.
As to CAA section 202(a), the 2008 ANPRM set out a framework for
determining whether ``GHG emissions from new motor vehicles cause or
contribute to air pollution that may reasonably be anticipated to
endanger public welfare'' under CAA section 202(a)(1) or for
``explain[ing] why scientific uncertainty is so profound that it
prevents making a reasoned judgment on such a determination.'' 73 FR
44398, 44421. We reviewed available information for CO<INF>2</INF>,
methane, and N<INF>2</INF>O emissions and noted that HFCs, PFCs, and
SF<INF>6</INF> are ``often grouped together'' and separately from the
rest ``because they contain fluorine, typically have large global
warming potentials, and are produced only through human activities.''
73 FR 44401-02.\25\ With respect to endangerment, we sought comment on
whether GHGs could properly be considered dangerous air pollution
because the potential health effects are indirect and the potential
welfare effects may be positive on balance. 73 FR 44427. In addition,
we sought comment on whether ``the unique characteristics and
properties of each GHG . . . as well as current and projected
emissions'' meant that each GHG should be analyzed individually or
whether certain GHGs other than CO<INF>2</INF> were amenable to
grouping. 73 FR 44428. With respect to causation or contribution, we
presented motor vehicle and engine emissions data for each GHG
separately and noted that emission trends had diverged between
pollutants, with CO<INF>2</INF> emissions, for example, generally
increasing since 1990 and N<INF>2</INF>O emissions, for example,
increasing from 1990 to 1995 and then falling substantially from 1995
to 2006 because of fuel and technology changes. 73 FR 44430. We also
presented extensive information on potential regulatory approaches that
could be triggered by a positive finding under CAA section 202(a),
including
[[Page 36295]]
approaches specific to particular GHGs. 73 FR 44438-63.
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\25\ In the 2008 ANPRM, the EPA noted that the most recently
available IPCC analysis concluded that ``[t]he anthropogenic
combined heating effect (referred to as forcing) of [methane],
N<INF>2</INF>O, HFCs, PFCs and SF<INF>6</INF> is about 40% as large
as the CO<INF>2</INF> cumulative heating effect since pre-industrial
times.'' 73 FR 44423.
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Following a change in administration, however, the EPA proposed in
April 2009 and finalized in December 2009 a much different approach to
analyzing GHG emissions from new motor vehicles and engines under CAA
section 202(a). In the Endangerment Finding, the Administrator found
that ``the science [was] sufficiently certain'' to compel an
affirmative determination and interpreted Massachusetts as ``allow[ing]
for the consideration only of science.'' 74 FR 66501. Relatedly, the
Administrator did not consider any of the implementation challenges or
options discussed in the 2008 ANPRM, asserting instead that CAA section
202(a) confers ``procedural discretion'' to issue standalone findings
without considering a regulatory response because the statute ``is
silent on this issue.'' Id. The Administrator also defined all six
``well-mixed'' GHGs collectively as the relevant ``air pollutants'' and
``air pollution'' for purposes of endangerment and causation or
contribution, meaning the Endangerment Finding did not need to address
the different characteristics or emission trends of any particular GHG.
74 FR 66516-21, 66536-57.
With respect to endangerment, the Administrator began by excluding
adaptation--human responses that reduce potential adverse impacts--and
mitigation--independent measures that reduce the causes of potential
adverse impacts--from the analysis of global climate change concerns.
74 FR 66513. The Administrator acknowledged that ``some level of
autonomous adaptation will occur'' and that ``this separation means
this approach may not reflect the actual conditions in the real world
in the future, because adaptation and/or mitigation may occur and
change the risks.'' Id. Nevertheless, the Administrator reasoned that
``it would be extremely hard to make a reasoned projection of human and
societal adaptation and mitigation responses'' because they are
``largely political'' or ``individual personal judgments.'' Id. Next,
the Administrator relied on IPCC Assessment Report 4 (AR4) projections
to find that global temperatures would likely increase between 1.8 to 4
degrees Celsius by 2100, with an uncertainty range of 1.1 to 6.4
degrees Celsius. 74 FR 66519. Operating within this analytical
framework, the Administrator found that elevated global concentrations
of GHGs from all foreign and domestic sources were responsible for
increased global temperatures that were responsible in turn for
indirect health risks driven by (1) more frequent heat waves; (2) air
quality effects, including increased formation of ozone, and (3)
broader societal impacts related to increased frequency and severity of
certain extreme weather events. 74 FR 66525.\26\ The Administrator also
found that GHG emissions could lead to welfare effects related to (1)
food production and agriculture; (2) forestry; (3) water resources; (4)
sea level rise; and (5) energy infrastructure and settlements, although
the evidence was uncertain for several categories that may see near-
term benefits. 74 FR 66531-35.\27\ Importantly, the Administrator
acknowledged that the understanding of public health and welfare in the
Endangerment Finding was atypical, particularly with respect to
considering indirect effects, but asserted the approach was necessary
given the ``unique'' challenge presented by global climate change. 74
FR 66527.
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\26\ The Administrator also noted that increased global
temperatures could lead to changes in certain food- and water-borne
pathogens and allergens (including increases in pollen resulting
from increased plant growth at higher concentrations of
CO<INF>2</INF>) but did ``not plac[e] primary weight on these
factors.'' 74 FR 66498, 66526.
\27\ The Administrator relied on welfare impacts to water
resources and sea level rise as providing ``the clearest and
strongest support for an endangerment finding.'' 74 FR 66534.
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With respect to contribution, the Administrator asserted broad
authority to interpret the statutory standard because ``[t]he language
of CAA section 202(a) is silent regarding how the Administrator is to
make her contribution analysis.'' 74 FR 66544. Exercising that putative
interpretive authority, the Administrator concluded that ``it is
reasonable to consider that lower percentages contribute than one may
consider when looking at a local or regional problem involving fewer
sources of emissions,'' 74 FR 66545, because ``all contributors must do
their part'' to avoid ``a tragedy of the commons, whereby no country or
source category would be accountable for contributing to the global
problem of climate change,'' 74 FR 66543. Next, the Administrator
relied on data showing that existing motor vehicles and engines emitted
four GHGs--CO<INF>2</INF>, methane, and N<INF>2</INF>O from engines, as
well as HFCs from air conditioning units--that accounted for 4.3
percent of global GHG emissions at the time. On that basis, the
Administrator found that GHG emissions from new motor vehicles and
engines ``contribute to the air pollution'' consisting of the six
``well-mixed'' GHGs previously identified as a danger to public health
or welfare. 74 FR 66537-39.
Crucially, the Endangerment Finding made clear that the EPA was
acting independently from any new congressional mandate. Rather, the
Administrator interpreted CAA section 202(a) as setting out a
standalone authority to issue findings that establish jurisdiction
without considering implementation concerns and purported to rest the
Endangerment Finding solely on a scientific judgment informed by the
record as assembled by the Agency in 2009.
D. Implementation of the 2009 Endangerment Finding
In the years since issuing the Endangerment Finding, the EPA has
promulgated GHG emission standards for various classes of new motor
vehicles and engines in reliance on the Endangerment Finding and, as
anticipated in the 2008 ANPRM, sought to expand the same analytical
framework to regulatory provisions governing existing vehicles,
stationary sources, aircraft, and oil and gas operations. For a full
accounting of GHG emission standards adopted since 2009 under CAA
section 202(a), see sections VI.B and VI.C of this preamble.
Following the Endangerment Finding, the EPA received multiple
petitions for reconsideration from industry groups, States, and various
organizations arguing that our approach in 2009 was legally and
scientifically flawed and that external assessments by the IPCC, among
others, had not adequately addressed recent criticisms of climate
change science. The EPA denied these consolidated petitions in 2010
without notice and comment. Reiterating the scientific assertions from
the technical support document (TSD) used in 2009, we emphasized that
we had conducted an independent review of outside assessments in
issuing the Endangerment Finding and asserted that the core conclusions
of the Endangerment Finding remained valid notwithstanding the flaws
raised by the petitioners. The EPA also issued a volume of response
documents defending the methodologies and experts relied upon and
concluded that no new information warranted reconsideration. 75 FR
49556.
In April 2022, the EPA denied, again without notice and comment, a
new round of petitions for reconsideration and rulemaking asserting
that the Endangerment Finding was legally and scientifically flawed and
undermined by more recent scientific assessments. We acknowledged that
several recent studies contradicted assessments by the USGCRP and IPCC
but reaffirmed our earlier position that such assessment reports are
entitled to greater weight
[[Page 36296]]
than dissenting views.\28\ We also considered criticisms of the EPA's
Social Cost of Carbon (SCC) methodology out of scope because ``the
social cost of carbon played no role in the 2009 Endangerment
Finding.'' \29\ We further acknowledged that severing the endangerment
and cause or contribute analysis from the development of subsequent
regulations had impacted the EPA's approach to GHG emission standards,
including because the Science Advisory Board (SAB) did not have the
opportunity to review the Endangerment Finding as would otherwise have
been required by the CAA.\30\ Nevertheless, we reaffirmed our position
that CAA section 202(a) grants ``procedural discretion'' to issue
findings and emission standards separately and ``decline[d] to exercise
that discretion'' differently.\31\
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\28\ 2022 Denial at 15-17.
\29\ Id. at 30.
\30\ Id. at 36 (noting that 42 U.S.C. 4365(c)(1) requires SAB
consultation for a ``standard'' promulgated under CAA section 202(a)
but asserting that requirement does not extend to ``findings''
issued under the same provision).
\31\ Id. at 39.
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E. Reconsideration of the 2009 Endangerment Finding
Since the EPA published the 2009 Endangerment Finding, there have
been developments in innovation, science, economics, and mitigation, as
well as significant Supreme Court decisions that provide new guidance
on how federal agencies should interpret the statutory provisions that
Congress has tasked them with administering.\32\ Accordingly, the
Administrator has now determined that the Endangerment Finding should
be reconsidered to address legal and scientific developments that
present reason to question the ongoing validity and reliability of its
conclusions and to subject these important issues to public comment for
the first time since 2009.
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\32\ See Feb. 19, 2025 Memo at 1.
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In initiating reconsideration, the Administrator explored all
findings, support, questions, and ambiguities contained within the
science relied upon by the Endangerment Finding. As acknowledged in the
Endangerment Finding and recent reports, there are significant
questions and ambiguities presented by both the observable realities of
the past nearly two decades and the recent findings of the scientific
community, including those summarized in the 2025 CWG Draft Report.
There may also be as-yet-unidentified issues or discrepancies present
in the underlying TSD and scientific justifications offered in the
Endangerment Finding. When confronted with science offering a diverse
array of conclusions, methodologies, and explanations, the
Administrator strove to inform his judgment to the most impartial
extent possible. A more detailed discussion of the available climate
science can be found in section IV.B.
III. Legal Framework for Proposed Action
A. Proposed Rescission of Endangerment Finding
The statutory authority for this proposed action is the same as
that relied upon in the prior actions at issue: CAA section 202(a)(1),
which requires the Administrator to ``prescribe'' and ``from time to
time revise . . . standards'' for certain air pollutants emitted by new
motor vehicles and new motor vehicle engines ``in accordance with the
provisions of this section.'' \33\ Unless provided otherwise by
statute, an agency may revise or rescind prior actions so long as it
acknowledges the change in position, provides a reasonable explanation
for the new position, and considers legitimate reliance interests in
the prior position.\34\
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\33\ 42 U.S.C. 7521(a)(1).
\34\ See Wages & White Lion, 145 S. Ct. 898; FCC v. Fox
Television Stations, Inc., 556 U.S. 502 (2009); Motor Vehicle Mfrs.
Ass'n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29 (1983); Clean
Air Council v. Pruitt, 862 F.3d 1, 8 (D.C. Cir. 2017) (``Agencies
obviously have broad discretion to reconsider a regulation at any
time.'').
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The EPA proposes that nothing in the language of the statute
prohibits or conditions our general authority to rescind prior actions.
CAA section 202(a)(1) grants the Administrator discretion to ``revise''
standards prescribed ``in accordance with the provisions of this
section'' and does not require retaining the same level of stringency
when revising or rescinding existing standards. Moreover, the statute
neither authorizes the Administrator to issue standalone findings that
trigger a duty to regulate nor prohibits the Administrator from
rescinding such findings. Rather, CAA section 202(a)(1) requires the
Administrator to prescribe standards for emissions of any air pollutant
by classes of new motor vehicles or engines when, in his judgment,
emissions of such air pollutant by such classes of new motor vehicles
or engines ``cause, or contribute to, air pollution which may
reasonably be anticipated to endanger public health or welfare.''
Notably, the EPA has consistently assumed that it has the statutory
authority to rescind the Endangerment Finding in reviewing the merits
of petitions for reconsideration since 2009 and did not state that we
lack such reconsideration authority.\35\
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\35\ See, e.g., 2022 Denial at 7-10 (denying mandatory
reconsideration under CAA section 307(d) and reviewing the petitions
on the merits as rulemaking petitions under APA section 553(e)); 75
FR 49560-63 (denying mandatory reconsideration under CAA section
307(d) without asserting that the EPA lacked statutory authority to
rescind or revise the Endangerment Finding).
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The EPA acknowledges that rescinding the Endangerment Finding as
proposed would involve significant changes to the legal interpretations
adopted in the Endangerment Finding and retained in subsequent actions.
For example, if finalized, the interpretation of CAA section 202(a)
proposed in this action would preclude the EPA from issuing standalone
endangerment and contribution findings and would instead require the
Agency to make findings for particular air pollutant emissions and
classes of new motor vehicles and engines as an integral step in a
rulemaking to prescribe standards for such emissions and classes,
consistent with our decades-long practice prior to 2009 in regulating
non-GHG air pollutants. Furthermore, if finalized, the interpretation
of CAA section 202(a) proposed in this action would reverse the basis
for the Endangerment Finding by concluding that global climate change
concerns cannot satisfy the statutory standard for regulation under CAA
section 202(a). For discussion of our proposed interpretation of CAA
section 202(a) and related statutory provisions, see section IV.A of
this preamble. For discussion of our alternative proposal to rescind
the Endangerment Finding because the EPA exercised its authority under
CAA section 202(a) unreasonably and because the Administrator no longer
has confidence in the assumptions, methodology, and conclusions in the
Endangerment Finding in light of the scientific record, see section
IV.B of this preamble.
The EPA is also proposing additional statutory and policy
rationales for repealing the GHG emission standards currently in effect
for new motor vehicles and engines separate and apart from the proposed
rescission of the Endangerment Finding. If finalized, these alternative
rationales would change the novel position taken in rulemakings since
2009 to prescribe and revise GHG emission standards under CAA section
202(a).\36\ For example, if finalized, our proposal to determine that
there is no ``requisite technology'' for
[[Page 36297]]
vehicle emission control capable of having a measurable impact on the
dangers identified in the Endangerment Finding would preclude any GHG
emission standards from going into effect. Furthermore, if finalized,
our proposal to determine that the GHG emission standards harm public
health and welfare on balance would make it unreasonable and contrary
to the objectives of the statute to issue and retain such standards.
See section V of this preamble for further discussion of these
additional rationales and the Agency's prior positions.
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\36\ 75 FR 25324 (May 7, 2010); 76 FR 57106 (Sept. 15, 2011); 77
FR 62624 (Oct. 15, 2012); 81 FR 73478 (Oct. 25, 2016); 85 FR 24174
(Apr. 30, 2020); 86 FR 74434 (Dec. 30, 2021); 89 FR 27842 (Apr. 18,
2024); 89 FR 29440 (Apr. 22, 2024).
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The EPA acknowledges that repealing the GHG emission standards
based on the proposed rescission of the Endangerment Finding would
depart from our position in rulemakings since 2009 that prescribed and
revised GHG emission standards for light- and medium-duty vehicles and
heavy-duty vehicles and engines under CAA section 202(a). If finalized
as proposed, the rescission would eliminate the statutory basis for
those standards because we relied on the Endangerment Finding in each
rulemaking to invoke our authority under CAA section 202(a) without
making the required findings for GHGs emitted by the class or classes
of new motor vehicles or engines at issue in each rulemaking. See
section VI of this preamble for further discussion of each prior
rulemaking and the regulatory changes that would be necessary to repeal
all GHG emission standards currently in effect for new motor vehicles
and engines on any of the bases proposed in this action.
As discussed throughout this preamble, the EPA is proposing these
changes to comply with limits on our statutory authority under the best
reading of CAA section 202(a), respond to legal and scientific
developments that undermine the conclusions and assumptions of the
Endangerment Finding, and realign Agency resources to prioritize core
statutory responsibilities. Importantly, the Nation's policy response
to global climate change concerns was a major issue in the 2024
presidential election, in which voters were presented with distinct
legal and policy approaches and elected a candidate promising a change
in policy. Under these circumstances, the election of a new
Administration is an independent and sufficient basis for changing
legal interpretation and policy within the boundaries set by
statute.\37\ Democratic accountability is essential to the exercise of
delegated authority by administrative agencies,\38\ and retaining the
Endangerment Finding without clear statutory authority would frustrate,
not promote, constitutional values and the rule of law. If the EPA
lacks authority to retain the Endangerment Finding under the best
reading of CAA section 202(a), the statute controls regardless of
policy preferences.
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\37\ See State Farm, 463 U.S. at 59 (Rehnquist, J., concurring
in part and dissenting in part); PETA v. USDA, 918 F.3d 151, 158
(D.C. Cir. 2019) (``new administrations are entitled to reevaluate
and modify agency practices, even longstanding ones''); Nat'l Ass'n
of Home Builders v. EPA, 682 F.3d 1032, 1043 (D.C. Cir. 2012) (``the
inauguration of a new President and the confirmation of a new EPA
Administrator'' went ``a long way toward explaining why EPA''
changed policy).
\38\ See, e.g., U.S. Telecom Ass'n v. FCC, 855 F.3d 381 (D.C.
Cir. 2017) (Brown, J., dissenting from denial of rehearing en banc);
Elena Kagan, Presidential Administration, 114 Harv. L. Rev. 2245,
2252-53, 2332-34 (2001).
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The EPA seeks comment on the nature and extent of any reliance
interests that may have arisen from our assertion of regulatory
authority over GHG emissions from new motor vehicles and engines and is
committed to assessing any such interests, determining whether they are
significant, and weighing such interests against competing rationales,
as required by law.\39\
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\39\ See, e.g., DHS v. Regents of Univ. of Cal., 591 U.S. 1, 33
(2020).
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Specifically, we seek comment on whether regulated parties have any
significant reliance interests in our GHG emission standards for new
motor vehicles and new motor vehicle engines. We are aware that
manufacturers, importers, and sellers have already expended resources
complying with GHG emission standards for MYs 2012 through 2026, and
that consumer prices for vehicles in these MYs reflect the costs of
such compliance. Because many compliance costs are incurred as part of
research and development and during manufacturing, with the notable
exception of the need to purchase compliance credits, this proposed
action would have limited impacts on MYs 2012 to 2024, greater impacts
for MYs 2024-2026, and would entirely relieve future regulatory
obligations for MY 2027 and beyond. As discussed in sections VI.B and
VI.C of this preamble, we are confident that the Agency has adequate
regulatory tools to address transitional compliance concerns and note
that this proposed action would not, if finalized, mandate any
particular response by regulated parties. We are also aware that
regulated parties may have reliance interests in national uniformity
and CAA preemption with respect to emission standards for new motor
vehicles and engines. As discussed in section VI.A of this preamble,
CAA section 209(a) and other applicable sources of federal preemption
would continue to apply, and we would retain our authority to regulate
emissions, including emissions of the six ``well-mixed'' GHGs addressed
in the Endangerment Finding, under circumstances that meet the standard
for regulation under CAA section 202(a). We seek comment on each of
these rationales, including on whether any reliance interests in
national uniformity and preemption would support finalizing or not
finalizing the proposed action, or adopting certain rationales and not
finalizing other rationales. We further seek comment on the continued
preemptive effect of the CAA in the event that the EPA finalizes the
proposed rescission or any of the alternatives discussed herein (or in
the event that the Agency determines that it lacks authority at the
present time to regulate GHG emissions under one or more provisions of
the CAA for any reason). As a general matter, we also seek comment on
how we should repeal the Endangerment Finding and regulations if the
decision is made to proceed with the proposed repeals, including under
any of the options set out in this proposal or any additional grounds
and means.
In addition, the EPA seeks comment on whether regulated parties and
other stakeholders have significant reliance interests in GHG emission
standards for new motor vehicles and engines. This proposed action
would make only minor conforming adjustments to regulatory provisions
for criteria pollutants and air toxics, thereby leaving most emission
standards for new motor vehicles and engines in place. Nor would this
proposed action impact separate economy and fuel-efficiency standards
that have the effect of reducing GHG emissions per mile traveled from
new motor vehicles and engines, including standards issued by NHTSA. As
explained in section IV.A.1 of this preamble, we now believe that
regulating GHG emissions based on global climate change concerns
exceeds our statutory authority under CAA section 202(a) and, as such,
propose that reliance interests alone would not justify retaining the
GHG emission standards that we lacked authority to prescribe. As
discussed in section IV.A.2 of this preamble, potential dangers from
local or regional exposure to the six ``well-mixed'' GHGs covered by
the Endangerment Finding are regulated separately under specific grants
of statutory authority. And as discussed in section V of this preamble,
we now believe that GHG emission standards for new motor vehicles and
engines may harm public health and
[[Page 36298]]
welfare without having any measurable impact on the global climate
change concerns identified in the Endangerment Finding. We seek comment
on potential reliance interests in GHG emission standards for global
climate change concerns under CAA section 202(a), including on whether
such reliance justifies retaining standards in the absence of statutory
authority and the extent to which potential dangers are addressed, or
could be addressed, under more specific authorities.
The EPA recognizes that we have relied in part on the Endangerment
Finding in issuing subsequent endangerment findings and GHG regulations
under other CAA provisions, including for certain stationary sources
and aircraft engines. The Supreme Court has since vacated several of
these actions, including GHG regulations for existing sources in the
fossil-fuel fired power plant source category under CAA section 111(d)
and for permitted sources under CAA Title V.\40\ For those actions that
remain in effect, we have initiated or intend to initiate separate
rulemakings that will address any overlapping issues.
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\40\ See West Virginia, 597 U.S. 697; UARG, 573 U.S. 302.
---------------------------------------------------------------------------
Among other concerns with the Endangerment Finding, we believe that
severing consideration of endangerment and causation or contribution
from the appropriate regulatory response under CAA section 202(a)
resulted in broad statements that did not account for the statutory
language in CAA section 202(a)(1) on which the Endangerment Finding
purported to rely. Congress used different authorizing language to
address distinct issues for stationary sources regulated under CAA
section 111 and aircraft engines regulated under CAA section 231. In
reconsidering actions taken under these authorities, we intend to
address prior findings and standards in light of the particular
statutory language, policy concerns, and scientific information
relevant to each context. In this proposed action, we seek comment on
reliance interests in the Endangerment Finding and GHG emission
standards issued under CAA section 202(a) and reserve the right to
direct out of scope comments to the appropriate rulemaking docket for
the applicable regulatory action.
B. Proposed Amendments to New Motor Vehicle and Engine Regulations
As noted above, CAA section 202(a)(1) directs the Administrator to
prescribe ``standards applicable to the emission of any air pollutant
from any class or classes of new motor vehicles or new motor vehicle
engines, which in his judgment cause, or contribute to, air pollution
which may reasonably be anticipated to endanger public health or
welfare.'' This core directive has remained substantially the same
since Congress enacted the Motor Vehicle Pollution Control Act of
1965.\41\ Thus, a necessary condition to regulating emissions from new
motor vehicles and engines is a finding--an ``endangerment finding''--
that emissions of an air pollutant from a class or classes of new motor
vehicles or engines cause or contribute to air pollution which may
reasonably be anticipated to endanger public health or welfare.
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\41\ Public Law 89-272, 79 Stat. 992-93.
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For the reasons discussed in section IV of this preamble, we are
proposing to rescind the Endangerment Finding for GHG emissions from
new motor vehicles and new motor vehicle engines and, on that basis, to
repeal all existing GHG emission standards for passenger cars, light-
duty trucks, motorcycles, buses, medium-duty vehicles, and heavy-duty
vehicles and engines. The Endangerment Finding has served as the EPA's
basis for regulating GHG emissions from new motor vehicles and new
motor vehicle engines since 2009. Absent findings of endangerment and
causation or contribution, the EPA lacks statutory authority to
prescribe standards for those emissions under CAA section 202(a)(1). We
propose that when the EPA rescinds an endangerment finding for an air
pollutant, it must cease prescribing and enforcing standards applicable
to the emission of that pollutant from new motor vehicles or new motor
vehicle engines and should rescind existing standards no longer
authorized by statute.
For the reasons discussed in section V of this preamble, we are
also proposing additional bases to repeal GHG emission standards even
if the Endangerment Finding were to remain in place. We propose that
regardless of whether GHG emissions trigger the standard for regulation
in CAA section 202(a)(1), our authority to prescribe and enforce
emission standards for GHGs is limited by the language of CAA section
202(a)(2) and must be exercised in a reasonable manner that furthers,
rather than burdens, the health and welfare of all Americans.
Accordingly, the EPA is proposing to repeal all standards and
associated test procedures adopted to limit the emission of GHGs under
CAA section 202(a) for highway light-, medium-, and heavy-duty vehicles
and engines. The EPA notes that, for light-duty vehicles, the Energy
Policy and Conservation Act of 1975 (EPCA) and the 2007 EISA authorize
NHTSA to administer the CAFE program and fuel economy labeling program.
These statutes also direct the EPA to determine compliance values for
manufacturers subject to the CAFE program and the fuel economy labeling
program. Importantly, these statutory obligations are distinct from the
EPA's authority under CAA section 202(a) and from the EPA's decisions
since 2009 to regulate GHG emissions under CAA section 202(a). As
explained in section VI of this preamble, we are retaining and not
proposing to reopen regulatory provisions related to our statutory
roles in these NHTSA programs. Likewise, we are retaining and not
proposing to reopen any criteria pollutant and air toxics standards for
highway light-, medium-, and heavy-duty vehicles and engines under CAA
section 202(a).
IV. Proposed Rescission of the Endangerment Finding
In this section, the EPA proposes to rescind the Endangerment
Finding by concluding, based on multiple, independent alternative legal
rationales, that the Agency's unprecedented foray into regulating GHG
emissions from new motor vehicles and engines is inconsistent with the
best reading of CAA section 202(a). Under any proposed alternative, the
EPA would lack authority to retain existing GHG emission standards for
new motor vehicles and engines and proceed to repeal the relevant
provisions of Title 40 of the CFR as proposed in section VI of this
preamble.
Section IV.A of this preamble describes our primary proposal to
rescind the Endangerment Finding by concluding that CAA section 202(a)
does not authorize the EPA to prescribe standards for GHG emissions
based on global climate change concerns or to issue standalone findings
that do not apply the statutory standard for regulation as a cohesive
whole. If finalized, this proposal would require rescinding the
Endangerment Finding and resulting regulations because we lacked
statutory authority to issue them in the first instance. We begin by
proposing the best reading of CAA section 202(a) and related
provisions, as informed by the Supreme Court's decisions in Loper
Bright and UARG. Next, we propose that the Nation's response to global
climate change concerns generally, and specifically whether that
response should include regulating GHG emissions from new motor
vehicles and engines, is an
[[Page 36299]]
economically and politically significant issue that triggers the major
questions doctrine under UARG and West Virginia, and that Congress did
not clearly authorize the EPA to decide it by empowering the
Administrator to ``prescribe . . . standards'' under CAA section
202(a). Throughout this section, we propose that the Endangerment
Finding relied on various forms of Chevron deference \42\ to depart
from the best reading of the statute and exceeded the EPA's authority
in several fundamental respects, any one of which would independently
require rescission to conform to the best reading of the law.
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\42\ Chevron U.S.A., Inc. v. NRDC, Inc., 467 U.S. 837 (1984),
overruled by Loper Bright, 603 U.S. 369; see 74 FR 66501, 66502,
66544 (asserting discretion based on statutory ambiguity, including
that created by silence); 74 FR 66528, 66542, 66543 (asserting
discretion based on statutory ambiguity).
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Section IV.B of this preamble describes the EPA's alternative
proposal that regardless of whether CAA section 202(a) authorizes
regulating GHG emissions based on global climate change concerns, we
would rescind the Endangerment Finding by concluding that the
Administrator analyzed endangerment and contribution in an unreasonable
manner. We begin by recounting the interpretation of CAA section 202(a)
adopted in the Endangerment Finding, which asserted ``procedural
discretion'' to issue standalone findings without prescribing the
standards required by such findings and to sever the analysis of
endangerment from the analysis of contribution. Next, we propose that
the Administrator exercised that discretion unreasonably by adopting an
approach that papered over substantial uncertainties in the scientific
record and failed to draw the required connection between GHG emissions
from a class or classes of new motor vehicles and global climate change
concerns. We further propose that developments since 2009 demonstrate
the uncertainties acknowledged in the Endangerment Finding are more
significant than previously believed, including because many of its
predictive judgments involve ranges of assumptions that largely fail to
satisfy the statutory standard for regulation and because the more
pessimistic assumptions have not been borne out in empirical data and
peer-reviewed studies through 2025. Finally, we propose that the
Administrator would exercise any discretion conferred by CAA section
202(a) differently to ensure a legally and scientifically sound
approach and that, under that approach, the Endangerment Finding and
resulting GHG emission standards must be rescinded.
We seek comment on every aspect of the primary and alternative
proposal, including the key issues on which we specifically request
comment as set out in section VII of this preamble.
A. Primary Rationale for Proposed Rescission
The Endangerment Finding announced an interpretation of CAA section
202(a) that permitted the EPA to prescribe standards in response to
global climate change concerns rather than local or regional exposures,
granted ``procedural discretion'' to issue standalone findings without
considering regulatory response, and severed the finding of
endangerment from the finding of contribution to that endangerment. At
the time, we assumed that statutory silence granted discretion to
construe the scope of our authority and asserted or implied that the
Supreme Court's decision in Massachusetts required us to read the
statute as authorizing the regulation of GHG emissions in response to
global climate change concerns.
In important respects, the Endangerment Finding and the Supreme
Court's decision in Massachusetts straddled a transitional period
regarding the standards for statutory interpretation and understandings
of agency authority. The breadth of agency discretion, and the question
whether Congress reserves major policy questions for itself, were
sharply disputed. Judicial decisions in the intervening fifteen years
have significantly clarified the law in both respects. In Loper Bright,
the Supreme Court expressly overturned the doctrine of deference to
agency statutory interpretation, ruling that statutes ``have a single,
best meaning'' that is informed, but not dictated, by Executive Branch
practice. 603 U.S. at 400-01. And in West Virginia, the Supreme Court
built upon its decisions in UARG and Brown & Williamson, among others,
by confirming that an agency must have more than ``a colorable textual
basis'' to claim authority to decide major questions of policy that
Congress would generally reserve for itself in the first instance. 597
U.S. at 723.
In this subsection, we propose that the best reading of CAA section
202(a), as informed by Loper Bright and principles of statutory
interpretation, does not authorize the EPA to assert jurisdiction over
GHG emissions based on global climate change concerns in a standalone
endangerment finding. Regardless whether GHGs are properly considered
``agents of air pollution'' under the general, Act-wide definition of
``air pollutant'' at CAA section 302(g), the EPA cannot regulate under
CAA section 202(a) unless the emissions of the air pollutant by a class
or classes of new motor vehicles ``cause, or contribute to, air
pollution which may reasonably be anticipated to endanger public health
or welfare.'' Because the text, structure, and history of CAA section
202(a) and related provisions demonstrate that this language targets
air pollution that threatens public health or welfare through local or
regional exposure, ``air pollution'' defined as six ``well-mixed'' GHGs
raising global climate change concerns that adversely impact a subset
of regions globally cannot satisfy this standard. We further propose
that this reading is independently confirmed and strengthened by the
major questions doctrine. Specifically, we propose that the major
questions doctrine applies and precludes the EPA from asserting
authority to regulate in response to global climate change concerns
under CAA section 202(a). At a minimum, Congress did not clearly
authorize the EPA to decide the Nation's response to global climate
change concerns by empowering the Agency to ``prescribe . . .
standards'' for certain air pollutants emitted by new motor vehicles
and engines. On these bases, and on account of the additional
procedural and analytical errors set out below, we propose that the
Endangerment Finding exceeded the EPA's authority and must be
rescinded.
1. Best Reading of CAA Section 202(a)
Congress originally enacted the language of CAA section 202(a) in
the Motor Vehicle Pollution Control Act of 1965 and retained it, with
minor revisions, in the 1970 CAA and all subsequent statutory
amendments. The key language in CAA section 202(a)(1) provides:
The Administrator shall by regulation prescribe (and from time
to time revise) in accordance with the provisions of this section,
standards applicable to the emission of any air pollutant from any
class or classes of new motor vehicles or new motor vehicle engines,
which in his judgment cause, or contribute to, air pollution which
may reasonably be anticipated to endanger public health or
welfare.\43\
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\43\ 42 U.S.C. 7521(a)(1).
Since 1977, CAA section 302(g) has defined the term ``air
pollutant'' throughout the statute as ``any air pollution agent or
combination of such agents . . . which is emitted into or otherwise
enters the ambient air.'' \44\
[[Page 36300]]
CAA section 302(h) also provides that any reference to ``effects on
welfare includes, but is not limited to, effects on'' the environment,
property, transportation hazards, and ``on economic values and on
personal comfort and well-being.'' \45\
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\44\ 42 U.S.C. 7602(g). Notably, the statute does not separately
define ``air pollution.''
\45\ 42 U.S.C. 7602(h).
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The EPA proposes that this statutory language is best read as
authorizing the Agency to identify and regulate, as an integral part of
a rulemaking prescribing emissions standards, air pollutants that cause
or contribute to air pollution that itself endangers public health and
welfare through local or regional exposures. This proposed
interpretation is consistent with the text and structure of the
statute, our decades-long implementation of the statute prior to 2009,
and background principles of statutory interpretation, including
default rules for proximate cause. This proposed interpretation is also
consistent with the Supreme Court's decision in Massachusetts, which
addressed distinct issues and must, as a matter of stare decisis, be
read in harmony with the Supreme Court's subsequent decisions bearing
on the EPA's authority and statutory interpretation in UARG, West
Virginia, and Loper Bright.\46\
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\46\ See Hohn v. United States, 524 U.S. 236, 252-53 (1998)
(Supreme Court decisions ``remain binding precedent until [the
Supreme Court] see[s] fit to reconsider them, regardless of whether
subsequent cases have raised doubts about their continuing
vitality.''); Rodriguez de Quijas v. Shearson/Am. Exp., Inc., 490
U.S. 477, 484 (1989) (similar).
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Dangerous Air Pollution. The EPA proposes that CAA section 202(a)
is best read as authorizing the Agency to regulate air pollutant
emissions that cause or contribute to air pollution that endangers
public health or welfare through local or regional exposure. For the
purposes of this proposed action, we use the phrase local or regional
exposure to distinguish air pollution that impacts public health and
welfare by its presence in the ambient air from ``air pollution''
consisting of six ``well-mixed'' GHGs that, as conceptualized in the
Endangerment Finding, impacts public health and welfare only indirectly
and not by its mere presence in the ambient air. As discussed below,
this proposal would effectively return the EPA to its interpretation of
CAA section 202(a) prior to 2009.
We propose that the terms ``air pollutant'' and ``air pollution''
as used in CAA section 202(a)(1) should be construed in accordance with
the specific air pollutants identified for other purposes in the
remainder of CAA section 202. Each of these listed air pollutants share
the common quality of causing or contributing to air pollution that
adversely impacts public health or welfare through local or regional
exposure to the air pollution itself. CAA section 202 specifically
addresses hydrocarbons (HCs), carbon monoxide (CO), oxides of nitrogen
(NO<INF>X</INF>), and particulate matter (PM), all of which harm health
and the environment through exposure (e.g., inhalation and dermal
contact) or by causing or contributing to air pollution that harms
health and the environment through exposure (e.g., smog and acid
rain).\47\ That pattern holds for the criteria pollutants identified in
the CAA--CO, lead, ground-level ozone (O<INF>3</INF>), nitrogen dioxide
(NO<INF>2</INF>), PM, and sulfur dioxide (SO<INF>2</INF>)--as well as
the initial list of hazardous air pollutants in CAA section
112(b)(1).\48\ We find it significant that in subjecting a number of
air pollutants emitted by new motor vehicles and engines to regulation
under CAA section 202, Congress did not include substances that are
potentially indirectly harmful to public health or welfare based on
elevated global concentrations in the upper atmosphere. That
conspicuous omission supports the conclusion that the air pollutants
subject to regulation under CAA section 202(a) are those that cause or
contribute to air pollution which itself endangers public health or
welfare through local or regional exposure.\49\
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\47\ See, e.g., 42 U.S.C. 7521(a)(3)(A)(i), (b), (g), (h), (j),
(k).
\48\ 42 U.S.C. 7412(b)(1).
\49\ As discussed in section IV.A.2 of this preamble, the only
references to GHGs in the CAA are in non-regulatory contexts in
which Congress authorized funding for various forms of research and
grant programs. The choice to limit such references to non-
regulatory solutions further supports the conclusion that the CAA
section 202(a) regulatory authority for responding to endangerment
does not encompass GHG emissions on the basis of global climate
change concerns.
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Put another way, we propose that the air pollutants identified in
CAA section 202 and throughout relevant provisions of the CAA are those
that cause or contribute to air pollution for which the air pollution
itself, through local or regional exposure to humans and the
environment, endangers public health or welfare.\50\ For certain
regulated air pollutants, the air pollutants are themselves the
dangerous air pollution, i.e., the air pollutants are the air pollution
with adverse health and welfare impacts. An example is CO, which can be
harmful, and even fatal, to humans at sufficient localized
concentrations.\51\ For other regulated air pollutants, the air
pollutants contribute to dangerous air pollution by interacting with
other airborne chemicals or environmental factors such as sunlight to
create the dangerous air pollution, i.e., the air pollutants are
ingredients that create the dangerous air pollution in combination. An
example is acid rain, in which air pollutants such as SO<INF>2</INF>
interact locally and regionally with additional airborne chemicals to
form acidic precipitation.\52\
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\50\ For example, unlike other regulated air pollutants,
``CO<INF>2</INF> is odorless, does not affect visibility and has no
toxicological effects at ambient levels,'' Additionally, the
Permissible Exposure Limit established by the U.S. Occupational
Safety and Health Administration or which diminished performance on
cognitive tasks are ``far larger than any plausible ambient outdoor
value through the end of the 22nd century.''Add 2025 CWG Draft
Report at 2.
\51\ U.S. Environmental Protection Agency. (Last updated Apr.
11, 2025). Carbon Monoxide's Impact on Indoor Air Quality: <a href="https://www.epa.gov/indoor-air-quality-iaq/carbon-monoxides-impact-indoor-air-quality">https://www.epa.gov/indoor-air-quality-iaq/carbon-monoxides-impact-indoor-air-quality</a>.
\52\ U.S. Environmental Protection Agency. (Last updated Mar. 4,
2025). What is Acid Rain?: <a href="https://www.epa.gov/acidrain/what-acid-rain">https://www.epa.gov/acidrain/what-acid-rain</a>.
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The definition of ``air pollutant'' in CAA section 302(g) and the
meaning of the undefined terms pollutant, pollution, and air pollution
support this reading. As a matter of ordinary language, a pollutant is
``[a] poisonous or noxious substance that contaminates the
environment,'' and pollution is ``[t]he harmful addition of a substance
or thing into an environment.'' \53\ Definitions of air pollution
similarly emphasize the emission of ``[c]ontaminants into the
atmosphere.'' \54\ The central concept is the addition of a
contaminant, something, that ``make[s] impure or unclean by contact or
mixture.'' \55\ CAA section 302(g) is consistent with these
definitions, adding only that an ``air pollutant'' is any ``air
pollution agent or combination of such agents'' that ``is emitted into
or otherwise enters the ambient air.'' \56\ Read together with CAA
section 202(a)--as the Supreme Court held we must in UARG--the
underlying concept of dangerousness and contamination reinforces the
conclusion that air pollution which endangers public health or welfare
is air pollution (caused or contributed to by air pollutants) that
itself endangers public health or welfare through local or regional
exposures.
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\53\ Black's Law Dictionary 1403 (11th ed. 2019).
\54\ Id.
\55\ Am. Heritage Dictionary (5th ed. 2022).
\56\ 42 U.S.C. 7602(g).
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The ``air pollution'' addressed in the Endangerment Finding is
different in kind. In that decision, the Administrator defined the
relevant ``air pollutants'' as six ``well-mixed GHGs'' and the relevant
``air pollution'' as ``the combined mix of'' these GHGs ``which
together,
[[Page 36301]]
constitute the root cause of human-induced climate change and the
resulting impacts on public health and welfare.'' 74 FR 66516. In
contrast to the air pollution addressed expressly in CAA section 202
and elsewhere in the statute, GHGs do not endanger public health or
welfare through local or regional exposure. Rather, the Endangerment
Finding asserted that GHG ``air pollution'' would lead to increases in
global temperature and change to ocean pH that, in turn, would lead to
environmental phenomena, in combination with an open-ended universe of
additional factors, which would potentially have adverse public health
and welfare impacts of varying severity in certain regions. Regulating
GHG emissions based on global climate change concerns requires reading
an additional instance of ``cause, or contribute'' into the statute,
such that CAA section 202(a) encompasses the `emission of air
pollutants that cause, or contribute to, dangerous air pollution that
causes, or contributes to, endangerment of public health or welfare.'
This proposed interpretation is also supported by the best reading
of the terms ``cause'' and ``contribute.'' In enacting and amending CAA
section 202(a), Congress legislated against background legal
principles, including principles of causation and proximate cause.\57\
These ``default rules'' are ``presumed to have [been] incorporated,
absent an indication to the contrary in the statute itself,'' \58\ and
nothing in the text of CAA section 202(a) indicates that Congress
intended to depart from ordinary legal meaning. As a general matter,
there is a point at which harm no longer has a sufficiently close
connection to the relevant conduct to reasonably draw a causal link. We
propose that emissions from new motor vehicles and new motor vehicle
engines in the United States do not have a sufficiently close
connection to the adverse impacts identified in the Endangerment
Finding to fit within the legal meaning of ``cause'' or ``contribute.''
The Endangerment Finding largely avoided addressing this problem by
severing the question whether GHG emissions from new motor vehicle
engines contribute to GHG concentrations in the atmosphere from the
question whether GHG concentrations in the atmosphere endanger public
health and welfare. As discussed in further detail in section IV.A.1 of
this preamble, we propose that there is no basis in the statute for
severing the inquiry in that way. Nevertheless, even with respect to
endangerment and contribution in isolation, we propose that global
climate change concerns involve analyzing causal relationships that are
too uncertain, too remote, and too confounded by intervening and
confounding factors to fit within the terms ``cause'' and
``contribute'' as used in CAA section 202(a). This understanding
follows from the position discussed above that CAA section 202(a) and
the statute more generally were designed to regulate air pollution with
harmful impacts from local and regional exposure that are analyzable by
ordinary causation standards.
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\57\ See, e.g., Bank of Am. Corp. v. City of Miami, 581 U.S.
189, 201 (2017); Lexmark Int'l, Inc. v. Static Control Components,
Inc., 572 U.S. 118, 132 (2014); Univ. of Tex. Sw. Med. Ctr. v.
Nassar, 570 U.S. 338, 347 (2013); City of Oakland v. Wells Fargo &
Co., 14 F.4th 1030 (9th Cir. 2021) (en banc).
\58\ Nassar, 570 U.S. at 347.
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In proposing this interpretation, we note that a limiting
construction is necessary to avoid absurd results and potential
conflict with the nondelegation doctrine. Because Congress cannot
delegate legislative powers to the Executive Branch, statutes granting
an agency regulatory authority must provide an intelligible principle
to guide its exercise.\59\ Our authority under CAA section 202(a) to
``prescribe . . . standards'' for air pollutant emissions by a class or
classes of new motor vehicles and engines is limited by the requirement
that the Administrator find such air pollutants cause or contribute to
air pollution that may reasonably be anticipated to endanger public
health and welfare. We propose that the best reading of the statute
circumscribes this authority to air pollution that itself causes or
contributes to endangerment of public health or welfare. Under the
interpretation adopted in the Endangerment Finding, however, our
authority under CAA section 202(a) would have no readily discernible
limiting principle, particularly in combination with the authority
asserted to sever the analysis of endangerment and causation or
contribution. Following the logic of the Endangerment Finding, any
``air pollutant'' emitted at more than de minimis volumes would trigger
our authority, and the statutory obligation, to prescribe standards so
long as the emission contributes to ``air pollution'' that, in turn,
potentially contributes to phenomena with predicted adverse impacts on
public health and welfare broadly defined. As discussed further below,
under this logic, the release of water vapor (H<INF>2</INF>O) would
meet the standard for regulation because water can be said to result in
significant harms and because motor vehicles and engines can be said to
``contribute'' to that harm by emitting non-de minimis quantities of
water vapor into the upper atmosphere. The EPA would have the
authority, and statutory duty, to prescribe standards for water vapor
emissions because water vapor is a recognized GHG emitted by motor
vehicles and engines as well as the vast majority of other mobile and
stationary sources. Because that reading effectively converts CAA
section 202(a)(1) into a roaming license to ``prescribe . . .
standards,'' we believe the reading proposed herein is more faithful to
the governing principles of statutory interpretation.
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\59\ See, e.g., Gundy v. United States, 588 U.S. 128 (2019).
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We further emphasize that this proposed interpretation would
effectively return the EPA to its longstanding practice prior to 2009
of applying CAA section 202(a) and related statutory endangerment
provisions to air pollution that adversely impacts public health and
welfare through local or regional exposure. As noted above, we
historically utilized this authority to prescribe standards for
pollutants identified in the CAA itself, including NO<INF>X</INF>, PM,
HC, and CO. The distinction between air pollution that harms public
health and welfare through local and regional exposure and global ``air
pollution'' consisting of GHG concentrations without any such direct
impacts has also played a role in our evaluation of waiver requests
under CAA section 209.\60\ Even in the Endangerment Finding, the
Administrator recognized that we had previously applied CAA section
202(a) to ``a more typical local or regional air pollution problem.''
74 FR 66538 (emphasis added). We propose that in adopting a novel
analytical approach in the Endangerment Finding, the EPA failed
adequately to address its prior practice and improperly relied on the
Supreme Court's decision in Massachusetts for the proposition that CAA
section 202(a) authorizes emission standards in response to air
pollution raising global climate change concerns. As discussed below,
Massachusetts did not construe the scope of the EPA's authority to
regulate under CAA section
[[Page 36302]]
202(a), and the Court has since made clear in UARG and West Virginia
that our authority to regulate air pollutants that fit within the Act-
wide definition turns on the particular statutory provision that
confers authority to regulate.
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\60\ See, e.g., ``California State Motor Vehicle Pollution
Control Standards; Notice of Decision Denying a Waiver of Clean Air
Act Preemption for California's 2009 and Subsequent Model Year
Greenhouse Gas Emission Standards for New Motor Vehicles,'' 73 FR
12156, 12161 (Mar. 6, 2008) (denying California's waiver request for
GHG emission standards on the ground that ``the different, and
global, nature of the pollution at issue'' requires a different
conceptual approach).
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In Massachusetts, the Supreme Court rejected the argument that GHGs
are not ``air pollutants'' under the Act-wide definition, reasoning
that CAA section 302(g)'s use of the word ``any'' in connection with
``air pollutant agent or combination of such agents, including any
physical [or] chemical . . . substance'' was sufficiently broad to
encapsulate the combination of GHGs at issue. 549 U.S. at 530. On this
basis, the Court stated that the EPA ``has the statutory authority to
regulate the emission of such gases from new motor vehicles.'' Id. at
532. The Court did not, however, decide whether including GHGs within
the definition of ``air pollutant'' meant that we must find that GHGs
meet the statutory standard for regulation under CAA section 202(a)
because they cause or contribute to air pollution which endangers the
public health or welfare. Rather the Court concluded its opinion by
clarifying that it ``need not and do[es] not reach the question whether
on remand EPA must make an endangerment finding.'' Id. at 534.
Consistent with Massachusetts, we propose to interpret the CAA as
setting out a broad, threshold definition of ``air pollutant'' on an
Act-wide basis that must be interpreted in the context of each
applicable, particular provision granting regulatory authority in order
to determine whether that provision authorizes the EPA to regulate an
air pollutant under that particular authority. For purposes of CAA
section 202(a), that means that even if GHGs are ``air pollutant[s]''
as defined on an Act-wide basis, they must meet the statutory standard
for regulating emissions from new motor vehicles and engines before we
may invoke our regulatory authority. Put simply, regardless whether
GHGs are ``air pollutants'' as defined in CAA section 302(g), they must
still satisfy the same standard as any other ``air pollutant'' by
causing or contributing to air pollution which may reasonably be
anticipated to endanger public health or welfare.
This understanding is confirmed by UARG, in which the Supreme Court
distinguished between ``the Act-wide definition'' of air pollutant and
the application of that definition to the Act's regulatory provisions.
573 U.S. at 320. The Court specifically addressed the holding in
Massachusetts, adopting the argument that ``while Massachusetts
rejected EPA's categorical contention that [GHGs] could not be air
pollutants for any purposes of the Act, it did not embrace EPA's [then]
current, equally categorical position that [GHGs] must be air
pollutants for all purposes regardless of the statutory context.'' Id.
(cleaned up).
In sum, we propose that CAA section 202(a) does not provide
authority to regulate GHGs based on global climate change concerns
because that provision authorizes regulating only air pollutants that
``cause, or contribute to, air pollution which may reasonably be
anticipated to endanger public health or welfare.'' The EPA must
``ground its reasons for action or inaction in the statute,''
Massachusetts, 549 U.S. at 535, and ``possess[es] only the authority
that Congress has provided,'' NFIB v. DOL, 595 U.S. 109, 117 (2022). In
proposing this interpretation, we note that our actions must be
consistent with ``the single, best meaning'' of the statute and cannot
expand our authority in response to pressing concerns based on
statutory silence or ambiguity. Loper Bright, 603 U.S. at 400, 411. We
seek comment on this proposed interpretation, including the rationales
articulated above and any further rationales that commenters believe
support, or detract from, this interpretation.
Findings and Standards. The EPA further proposes that CAA section
202(a) requires issuing emission standards together with the findings
necessary to invoke our regulatory authority, rather than severing the
regulatory action into separate endangerment and standards-setting
proceedings. The statute begins by providing that the Administrator
``shall prescribe . . . standards applicable to the emission of any air
pollutant from any class or classes of new motor vehicles or new motor
vehicle engines,'' and follows this requirement by describing the scope
of the duty to regulate air pollutant emissions ``which, in his
judgment cause, or contribute to, air pollution which may reasonably be
anticipated to endanger public health or welfare.'' We propose that the
best reading of the statute requires the Administrator, when
prescribing any emission standard for new motor vehicles or engines, to
find that the air pollutant or air pollutants emitted by the class or
classes of new motor vehicles or engines subject to the standard cause
or contribute to air pollution that may reasonably be anticipated to
endanger public health or welfare.
The Endangerment Finding severed this statutory language by finding
endangerment and contribution in the abstract for all potential CAA
section 202(a) sources with respect to GHGs. In so doing, the
Administrator vastly increased the Agency's authority by removing the
restrictions Congress placed on the issuance of emission standards. As
a result of this new conception of authority, the EPA may issue a
single endangerment finding in the abstract with respect to emissions
from all sources potentially subject to CAA section 202(a) (and their
existing-source counterparts) without addressing the danger posed by
any particular source category or the causal role of that particular
source category in any identified danger. The EPA has since relied on
the Endangerment Finding to prescribe emission standards for various
classes of new motor vehicles and engines, as well as a variety of
other sources under distinct statutory authorities, without making the
requisite findings or assessment of factors necessary to regulate the
sources in question.\61\ We propose that Congress enacted CAA section
202(a) as an integrated regulatory provision for a reason, and that
giving effect to the language of the statute requires the issuance of
emission standards only when the Administrator has made an integrated
finding of both endangerment and cause or contribution. Put another
way, we propose that it is impermissible for the Administrator to make
an endangerment finding without prescribing the emission standards
required in response to such a finding, and conversely, that it is
impermissible to prescribe emission standards without making the
source- and air-pollutant specific findings required by the statute.
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\61\ See sections II.C, VI.B, and VI.C of this preamble for a
summary of the EPA's rulemaking activities in response to the
Endangerment Finding.
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This proposed interpretation is consistent with the EPA's
implementation of CAA section 202(a) and similar provisions of the CAA
prior to 2009. In the Endangerment Finding, the Administrator
acknowledged that ``typically endangerment and cause or contribute
findings have been proposed concurrently with proposed standards under
various sections of the CAA, including CAA section 201(a).'' 74 FR
66501. We propose that our historical practice under CAA section 202(a)
reflects the better reading of the statute and is entitled to greater
weight. As the Supreme Court recently explained, such weight is
``especially warranted when an Executive Branch interpretation was
issued roughly contemporaneously with enactment of the statute and
remained consistent over time.'' Loper Bright, 603 U.S. at 386.
[[Page 36303]]
In departing from the EPA's historical practice in the Endangerment
Finding, the Administrator reasoned that ``[t]he text of CAA section
202(a) is silent on this issue'' and ``invoked the procedural
discretion that is provided by CAA section 202(a)'s lack of specific
direction.'' 74 FR 66501. We propose that CAA section 202(a) is not
silent on the issue because the statute sets out an integrated process
that requires the EPA to prescribe standards when the Administrator
finds certain conditions are met. When Congress intends a multi-step
inquiry in the environmental context, it typically says so expressly.
In the National Ambient Air Quality Standards (NAAQS) program, for
example, the CAA separates our authority to establish and revise the
NAAQS under CAA section 108 and 109 from our duties to implement the
NAAQS by reviewing State Implementation Plans (SIPs) or promulgating
Federal Implementation Plans (FIPs) under CAA section 110 and related
statutory provisions.\62\ A particularly relevant analogy is Clean
Water Act section 303(c)(4), which pairs the Administrator's authority
to ``determin[e] that a revised or new [water quality standard] is
necessary to meet the requirements of this chapter'' with the
requirement that the Administrator ``shall promptly prepare and publish
proposed regulations'' after making such a determination and
``promulgate any revised or new standard . . . not later than ninety
days after he publishes such proposed standards.'' \63\ We further
propose that even if CAA section 202(a) were ambiguous or silent in
this respect, the Supreme Court recently held in no uncertain terms
that ``statutory ambiguity . . . is not a reliable indicator of actual
delegation of discretionary authority to agencies.'' Loper Bright, 603
U.S. at 411.
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\62\ See 42 U.S.C. 7408, 7409, 7410.
\63\ 33 U.S.C. 1313(c)(4), (c)(4)(B). Various provisions of the
Safe Drinking Water Act (SDWA) and Toxic Substances Control Act
(TSCA) similarly articulate multi-step processes for determining
risk and addressing risk through regulation using language that
Congress did not include in CAA section 202.
---------------------------------------------------------------------------
Severing the EPA's standards-setting authority from the findings
that trigger a duty to exercise that authority shaped the analysis in
the Endangerment Finding in a manner that we propose ran counter to the
statute. Recall that the Endangerment Finding first projected adverse
public health and welfare impacts of global climate change and
attributed those adverse impacts to all manmade sources of GHG emission
around the world and then, separately, used data from existing CAA
section 202(a) sources in the United States to find that new motor
vehicles and engines in the United States contributed to global GHG air
pollution. The Administrator treated adaptation (adjustments to the
effect of climate change that lessen impacts) and mitigation
(reductions in emissions and global GHG concentrations unrelated to CAA
section 202(a) regulation) as outside the scope. 74 FR 66512. Moreover,
the Administrator declined to consider cost, asserting that the
Endangerment Finding imposed no regulatory requirements as a standalone
action and relying on the Supreme Court's decision in Whitman v.
American Trucking Association, 531 U.S. 457 (2001), that the EPA cannot
consider cost in setting and revising the NAAQS under CAA section 109.
74 FR 66515. Nor did the Administrator consider potential beneficial
impacts from climate change with respect to whether and which standards
would be appropriate. See 74 FR 66524 (purporting to compare ``risks
and benefits'' only with respect to endangerment).
Severance also shaped all subsequent standards prescribed and
revised in reliance on the Endangerment Finding in a manner we propose
to conclude was unlawful. The EPA asserted in subsequent rulemakings
that there was no need to make particularized findings for the relevant
source category because the Endangerment Finding identified public
health and welfare dangers and contribution for all CAA section 202(a)
source categories. Nor did we consider the impacts of adaptation or
mitigation or consider when prescribing standards whether, in light of
more recent empirical data, the Endangerment Finding's analysis of
endangerment and contribution remained accurate with respect to the
source category at issue. As a result, the decision to sever meant that
the EPA has never meaningfully considered or invited public comment on
the cost, effectiveness, and continued propriety of its GHG regulatory
program.
We propose that these considerations should have been taken into
account when the 2009 Endangerment Finding intentionally triggered a
duty to regulate by invoking our CAA section 202(a) authority. CAA
section 202(a)(2) expressly provides that ``[a]ny regulation prescribed
under paragraph (1) of this subsection . . . shall'' provide adequate
time for ``the development and application of the requisite technology,
giving appropriate consideration to the cost of compliance within such
period.'' \64\ CAA section 202(a)(1) authorizes the Administrator to
``by regulation prescribe'' standards ``in accordance with the
provisions of this section'' and does not separately authorize
standalone findings, meaning any action taken ``under paragraph (1) of
this subsection'' is subject to the considerations in paragraph (2).
That statutory language aside, the Supreme Court explained in Michigan
that ``agency action is lawful only if it rests `on a consideration of
the relevant factors,' '' 576 U.S. at 750 (quoting State Farm, 463 U.S.
at 43), including ``at least some attention to cost,'' id. at 752. We
propose that the Administrator erred in analogizing to the NAAQS
program and the Supreme Court's decision in Whitman to avoid
considering costs in the Endangerment Finding. Unlike CAA section
202(a), the language in CAA section 109(b) makes no reference to cost
or implementation and focuses solely on safety and an adequate margin
to protect public health. Nor does CAA section 109(b) include the lead
time and technical feasibility concepts embedded in CAA section 202(a).
And whereas CAA section 202(a) sets out an integrated authority to
prescribe emission standards when the provision's triggering condition
is satisfied, CAA section 109(b) uses mandatory language requiring the
EPA to establish certain standards, the content and implementation of
which are specified in various provisions throughout Title I of the
Act. We further propose that the Supreme Court's decision in
Massachusetts did not address the question whether the EPA could issue
standalone findings or bar the Administrator from taking cost and
implementation concerns into account when exercising CAA section 202(a)
authority. Rather, Massachusetts must be read together with Michigan,
and the language of CAA section 202(a)(1) must be read in context to
``produc[e] a substantive effect that is compatible with the rest of
the law.'' UARG, 573 U.S. at 321 (quoting United Sav. Ass'n of Tex. v.
Timbers of Inwood Forest Assocs., 484 U.S. 365, 371 (1988)).
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\64\ 42 U.S.C. 7521(a)(2).
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Endangerment and Cause or Contribute. The EPA also proposes that
CAA section 202(a) requires the Agency to evaluate whether source
emissions cause or contribution to air pollution and whether that air
pollution poses endangerment in a single causal chain, rather than
considering these issues in isolation by severing the inquiries. The
relevant inquiry is whether ``the emission of any air pollutant from
any class or classes of new motor vehicles or
[[Page 36304]]
new motor vehicle engines,'' in the judgment of the Administrator,
``cause, or contribute to, air pollution which may reasonably be
anticipated to endanger public health or welfare.'' As explained in
this section, the emission must cause or contribute to the danger posed
by the air pollution to a sufficient extent to satisfy the standard for
regulation.
In the Endangerment Finding, the Administrator made two distinct
findings based on two distinct sets of assumptions. In the first, the
Administrator found that the ``air pollution,'' defined as the combined
elevated global concentrations in the upper atmosphere of six ``well-
mixed GHGs,'' CO<INF>2</INF>, methane, NO<INF>X</INF>, HFCs, PFCs, and
SF<INF>6</INF>, endangered public health or welfare by playing a causal
role in global temperature increases and ocean pH changes, which, in
turn, were then asserted to play a causal role in environmental
phenomena with adverse impacts on public health and welfare. 74 FR
66516. In the second, the Administrator found that the ``air
pollutant'' (defined as the combination of same six ``well-mixed
GHGs'') emitted by new motor vehicles and engines contributed to the
``air pollution.'' 74 FR 66536. Nowhere in the Endangerment Finding did
the Administrator consider the extent to which emissions from CAA
section 202(a) sources have a more than de minimis effect on the danger
identified with respect to elevated concentrations of GHGs in the upper
atmosphere--let alone whether emissions from any particular class or
classes of sources that EPA intended to regulate had such an effect.
Upon review, we no longer believe that the approach taken in the
Endangerment Finding was consistent with the language of CAA section
202(a) and the structure of the CAA, which requires making distinct
findings for regulating distinct types of emission sources and
authorizes different regulatory tools when such standards are met. For
example, CAA section 111(b)(1)(A) authorizes the EPA to regulate
emissions from listed categories of stationary sources if the
Administrator determines those sources emit air pollutants that
``significantly contribute'' to dangerous air pollution.\65\ When that
standard is met, CAA section 111(b)(1)(B) requires the EPA to regulate
such emissions from such sources by setting standards of performance
that, among other things, reflect the best system of emission reduction
that has been adequately demonstrated in practice.\66\ The CAA
similarly sets out distinct standards for regulating and distinct modes
of regulation for additional major source categories, including
vehicles in use, aircraft engines, and separately addresses when and
how to respond to international emissions that impact the United
States. The Endangerment Finding effectively attributed the total GHG
emissions coming from all of these various distinct sources within the
United States, as well as from all international sources, to the mobile
sources regulated under CAA section 202(a) without having made the
requisite determinations for any of those sources and without
considering the different regulatory tools Congress authorizes for
those sources as compared to CAA section 202(a) sources. The
Administrator defined the relevant ``air pollution'' as the combination
of six ``well-mixed GHGs'' but found that CAA section 202(a) sources
emitted only four of them: CO<INF>2</INF>, methane, NO<INF>X</INF>, and
HFCs. 74 FR 66538. As a result, the ``air pollution'' identified as
endangering public health or welfare included PFCs and SF<INF>6</INF>,
and the ``air pollution'' used to conclude that CAA section 202(a)
sources satisfy the regulatory standard did not. Contrary to the EPA's
conclusion at the time, 74 FR 66541, that difference is material, as
PFCs and SF<INF>6</INF> are asserted to have many times the global
warming potential of CO<INF>2</INF>.\67\ Severing the endangerment and
cause-or-contribute analysis allowed the Agency to compare apples and
oranges in a manner the statute does not authorize.
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\65\ 42 U.S.C. 7411(b)(1)(A).
\66\ 42 U.S.C. 7411(a)(1), (b)(1)(B). CAA section 111 also
differentiates between new and existing stationary sources in a
listed source category and limits the EPA's role with respect to
existing sources by authorizing only emission guidelines implemented
by the States. 42 U.S.C. 7411(d).
\67\ U.S. Environmental Protection Agency. (Last updated Jan.
16, 2025). Understanding Global Warming Potentials: <a href="https://www.epa.gov/ghgemissions/understanding-global-warming-potentials">https://www.epa.gov/ghgemissions/understanding-global-warming-potentials</a>.
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The Endangerment Finding also did not limit its analysis of
contribution to ``new motor vehicles or new motor vehicle engines'' in
the United States, which are the only sources covered by the EPA's CAA
section 202(a) authority.\68\ Because the Administrator considered all
sources in analyzing the danger posed by elevated concentrations of
GHGs in the upper atmosphere, the endangerment analysis necessarily
included emissions from foreign and domestic vehicles that had been in
use for years or decades and were not ``new.'' Even when analyzing
contribution, the Administrator used emission estimates from ``the
entire fleet of motor vehicles in the United States for a certain
calendar year'' rather than projecting emissions from new motor
vehicles and engines over time. 74 FR 66543. That decision increased
the absolute contribution figure by orders of magnitude, including
because newer vehicles and engines tend to be more efficient and emit
less.\69\ Difficulties in disaggregating emission data from emission
sources, however reasonable, do not license us to read the term ``new''
out of the statutory text.
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\68\ 42 U.S.C. 7521(a)(1) (emphases added).
\69\ For additional discussion of improvements in new motor
vehicles and engines relative to older vehicles and engines, see
section V of this preamble.
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We are also concerned that severing the endangerment and cause or
contribution findings leads to untenable results and lacks any limiting
principle. To illustrate the problem, the same logic would allow the
EPA to issue emission standards for water vapor (H<INF>2</INF>O),
another substance emitted by new motor vehicles and engines that is
also considered a powerful GHG. Considered in isolation, H<INF>2</INF>O
concentrations in the atmosphere can be said to endanger public health
or welfare by resulting in rain that leads to slip-and-fall injuries,
drownings, and damage to crops, livestock, and property, including
through pools, rivers, and floodwater, although water vapor is not
itself harmful and is necessary to sustain life. Also considered in
isolation, CAA section 202(a) sources can be said to ``contribute'' to
elevated H<INF>2</INF>O concentrations in the atmosphere from all
anthropogenic sources, and these emissions of water vapor would thereby
assertedly ``contribute'' to global climate effects similar to those
attributed to other GHGs. CAA section 202(a) does not contemplate
prescribing emission standards for such an omnipresent, naturally
occurring, and essential component of the ambient air, and stakeholders
have not petitioned for such regulation, because the text requires
analyzing the extent to which emissions contribute to the danger. The
logic of regulating water vapor would appear to be absurd, but it is
the same logic required to regulate GHGs under CAA section 202(a).
We further propose that the decision to sever the analysis of
endangerment from the analysis of contribution, combined with the
decision to sever the Administrator's findings from any standards
prescribed as a result, produced an analysis that is incompatible with
the statute. In the Endangerment Finding, the Administrator concluded
that anything more than a trivial or de minimis
[[Page 36305]]
contribution to elevated global GHG concentrations by CAA section
202(a) sources was sufficient to trigger regulation because the
``unique, global aspects of the climate change problem tend to support
contribution at lower percentage levels of emissions than might
otherwise be considered appropriate when addressing a more typical
local or regional air pollution problem.'' 74 FR 66538. Because the
Endangerment Finding did not consider the standards that the statute
requires when the Administrator makes such a finding, we did not
consider whether emission standards for new motor vehicles would be
futile as a means to address the identified dangers of GHG emissions
from all anthropogenic sources. As discussed in sections IV.A and IV.B
of this preamble, reducing GHG emissions from all vehicles and engines
in the United States to zero would not have a scientifically measurable
impact on GHG emission concentrations or global warming potential (2025
CWG Draft Report at 130).\70\ It was foreseeable at the time that
issuing the Endangerment Finding would trigger a duty to regulate, and
that extraordinarily stringent measures would be necessary under all of
the EPA's separate statutory authorities, and not just CAA section
202(a), to have any potentially measurable impact on the identified
harm. Additionally, the EPA did not consider ``carbon leakage,'' which
``refers to the situation that may occur if, for reasons of costs
related to climate policies, businesses were to transfer production to
other countries with laxer emission constraints . . . [and] could lead
to an increase in their total emissions.'' \71\ Foreign governments
have recognized that carbon leakage can mitigate or even lead to an
increase in total emissions which would significantly impact the
claimed benefits of the regulatory actions.\72\ Accordingly, we propose
that refusing to consider these foreseeable consequences was
inconsistent with the statutory scheme and, as explained further below,
arbitrary and capricious and an abuse of discretion.
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\70\ See Lomborg, B. (2016). Impact of Current Climate
Proposals. Global Policy, 7(1) 109-118: <a href="https://doi.org/10.1111/1758-5899.12295">https://doi.org/10.1111/1758-5899.12295</a>.
\71\ Carbon leakage. (2019). European Commission: <a href="https://climate.ec.europa.eu/eu-action/eu-emissions-trading-system-eu-ets/free-allocation/carbon-leakage_en">https://climate.ec.europa.eu/eu-action/eu-emissions-trading-system-eu-ets/free-allocation/carbon-leakage_en</a>.
\72\ See, e.g., id.
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Finally, we propose that the Administrator did not adequately
consider the meaning in context of the statutory term ``endanger'' and
failed to identify with sufficient rigor the purported danger linked to
GHG emissions from new motor vehicles and engines. We propose that
``endanger'' as used in CAA section 202(a) cannot mean merely any
predicted negative impact to any public health or welfare value, as
that interpretation would render the constraint placed on the EPA's
authority to prescribe standards essentially meaningless, thereby
violating ordinary principles of statutory interpretation and raising
constitutional nondelegation concerns. We further propose that severing
the endangerment and contribution inquiries improperly allowed the
Administrator to avoid this concern by concluding that new motor
vehicle and engine emissions included more than de minimis GHG
emissions, even if those emissions did not themselves contribute to a
danger in any meaningful sense. See 74 FR 66543 (asserting that
``contributors must do their part even if their contributions to the
global problem, measured in terms of percentage, are smaller than
typically encountered''). We therefore seek comment on whether this
aspect of EPA's interpretation and application of the statutory
provision in 2009 was defective and whether, either on its own or in
combination with the other bases and rationales presented here, this
issue provides additional grounds for rescinding the Endangerment
Finding and resulting GHG emission standards for new motor vehicles and
engines.
2. Lack of Clear Congressional Authorization
The EPA further proposes that, at a minimum and in addition to the
interpretation set out above, we lack the ``clear congressional
authorization'' required under the major questions doctrine to decide
the Nation's response to global climate change concerns. West Virginia,
597 U.S. at 723 (quoting UARG, 573 U.S. at 324). In this subsection, we
propose that the major questions doctrine applies to the Endangerment
Finding because the global climate change concerns addressed in that
action, and the mandatory duty to regulate triggered by that action,
present a major question of undeniable political and economic
significance. Next, we propose that Congress did not clearly authorize
the EPA to decide this question when it empowered the Administrator to
``prescribe . . . standards'' for new motor vehicle and engine
emissions under CAA section 202(a). On that basis, we propose to
conclude that the Endangerment Finding and resulting GHG emission
standards exceeded our statutory authority and should be rescinded.
That conclusion follows from the Supreme Court's decisions in UARG and
West Virginia and is consistent with Massachusetts, which held that
GHGs fell within the definition of ``air pollutant'' but did not
interpret the scope of our authority to regulate air pollutants that
cause, or contribute to, air pollution which may reasonably be
anticipated to endanger public health or welfare.
Applicability of the Major Questions Doctrine. In recent decisions
construing the scope of the EPA's statutory authority to regulate GHGs,
the Supreme Court has emphasized that the `` `history and breadth of
the authority' '' asserted by an agency and ``the `economic and
political significance' of that assertion'' provide ```a reason to
hesitate before concluding that Congress' meant to confer such
authority.'' West Virginia, 597 U.S. at 721 (quoting Brown &
Williamson, 529 U.S. at 159-60); accord UARG, 573 U.S. at 324. Whether
viewed as an ordinary tool of statutory interpretation that looks to
the structure of the regulatory scheme \73\ or a clear statement rule
that implements nondelegation and separation of power principles,\74\
the major questions doctrine requires us to identify ``more than a
merely plausible textual basis'' when asserting authority to decide a
significant policy issue on Congress' behalf. Id. at 723.
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\73\ Biden v. Nebraska, 600 U.S. 477, 507-21 (2023) (Barrett,
J., concurring).
\74\ West Virginia, 597 U.S. at 735-51 (Gorsuch, J.,
concurring).
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In UARG, the Supreme Court applied the major questions doctrine to
reject our attempt to regulate GHG emissions from stationary sources
subject to the CAA's prevention of significant deterioration (PSD) and
Title V permitting requirements based on the global climate change
concerns identified in the Endangerment Finding. 573 U.S. at 311-
13.\75\ The Court held that the EPA had ``exceeded its statutory
authority when it interpreted the Clean Air Act to require PSD and
Title V permitting for stationary sources based on their greenhouse gas
emissions'' and ``may not treat greenhouse gases as a pollutant'' in
the PSD and Title V contexts. Id. at 333. In reaching this conclusion,
the Court found that our interpretation of the statute and related
``tailoring rule'' that exempted many sources to address workability
concerns was ``unreasonable because it would bring about an enormous
and transformative expansion in EPA's regulatory authority without
clear congressional authorization.'' Id. at 324. Citing earlier major
questions doctrine
[[Page 36306]]
precedents, the Court noted that ``a measure of skepticism'' is
required when ``an agency claims to discover in a long-extant statute
an unheralded power to regulate `a significant portion of the American
economy,' '' id. (quoting Brown & Williamson, 529 U.S. at 159), and
that ``[w]e expect Congress to speak clearly if it wishes to assign to
an agency decisions of vast `economic and political significance,' ''
id. (quoting Brown & Williamson, 529 U.S. at 160).
---------------------------------------------------------------------------
\75\ See 42 U.S.C. 7470-92, 7661 et seq.
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In West Virginia, the Supreme Court again applied the major
questions doctrine to reject our attempt to shift the power grid away
from using fossil fuels through GHG emission guidelines for existing
power plants under CAA section 111(d). 597 U.S. at 711-15.\76\ The
Court noted that when interpreting a grant of regulatory authority, the
inquiry includes the question ``whether Congress in fact meant to
confer the power the agency has asserted.'' Id. at 721. The Court
explained that the major questions doctrine applies when ``the `history
and breadth of the authority that [the agency] has asserted,' and the
`economic and political significance' of that assertion, provide `a
reason to hesitate before concluding that Congress' meant to confer
such authority.'' Id. (quoting Brown & Williamson, 529 U.S. at 159-60).
In such cases, ``both separation of powers principles and a practical
understanding of legislative intent make us `reluctant to read into
ambiguous statutory text' the delegation claimed to be lurking there,''
and ``[t]he agency instead must point to `clear congressional
authorization' for the power it claims.'' Id. at 723 (quoting UARG, 573
U.S. at 324). Applying that standard, the Court held that our statutory
authority to establish emission limits under CAA section 111(a)(1) and
(d) ``is not close to the sort of clear authorization required by our
precedents.'' Id. at 732.
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\76\ See 42 U.S.C. 7411(d). The EPA had also issued GHG
performance standards for new and modified fossil fuel-fired power
plants under CAA section 111(b) that triggered the Agency's
authority to issue guidelines for existing sources under CAA section
111(d). The new source standards were not before the Supreme Court
in West Virginia.
---------------------------------------------------------------------------
We propose that the Endangerment Finding implicates the major
questions doctrine for the same reasons the Supreme Court applied it in
UARG and West Virginia. By asserting jurisdiction to regulate in
response to global climate change concerns, the EPA `` `claim[ed] to
discover in a long-extant statute an unheralded power' representing a
`transformative expansion in [its] regulatory authority.' '' West
Virginia, 597 U.S. at 724 (quoting UARG, 573 U.S. at 324). We note that
the regulatory actions reviewed in UARG and West Virginia were
predicated in part on the Endangerment Finding and propose that the PSD
and Title V rules in UARG and existing source emission guidelines in
West Virginia are similar in scope, approach, and economic impact as
the GHG emission standards for new motor vehicles and engines
promulgated to fulfill the mandatory duty triggered by the Endangerment
Finding. As a consequence of the novel approach taken in the
Endangerment Finding to endangerment and contribution, our GHG emission
standards mandate an increased and faster shift from gasoline-fueled
vehicles to electric vehicles on the theory that a substantial
reduction in GHG emissions is necessary to address global climate
change concerns.\77\ We propose that mandating a shift in the national
vehicle fleet from one type of vehicle to another is indistinguishable
from the emission guidelines at issue in West Virginia, which were
calculated to force a shift from one means of electricity generation to
another.
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\77\ 89 FR 27842, 27844.
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We further propose it is `` `highly unlikely that Congress would
leave' to `agency discretion' the decision'' of how much gasoline
should be used by vehicles and engines in the United States. West
Virginia, 597 U.S. at 729 (quoting MCI Telecomms. Corp. v. AT&T Co.,
512 U.S. 218, 231 (1994)). As the Supreme Court noted with respect to
coal-based electricity generation, such a policy decision involves
``basic and consequential tradeoffs,'' and ``Congress certainly has not
conferred a like authority upon EPA anywhere else in the Clean Air
Act.'' Id. Until the Endangerment Finding, moreover, we had never
invoked CAA section 202(a) or any other CAA authority to regulate in
response to global climate change concerns, whether through a fuel-
shifting strategy or any other means. That history is telling because
although CAA section 202(a) has existed in substantially similar form
since 1967, ``the EPA had never regulated in that manner, despite
having issued many prior rules governing'' vehicle and engine
emissions. Id.
When Congress has addressed GHGs individually or collectively, it
has not granted the EPA broad regulatory authority comparable to our
authority to ``prescribe . . . standards'' under CAA section 202(a).
With respect to HFCs, Congress enacted a comprehensive phaseout scheme
in the 2020 American Innovation and Manufacturing (AIM) Act, which
includes detailed instructions, timelines, and requirements for
implementation and allows some uses to continue under certain
conditions.\78\ With respect to CO<INF>2</INF>, Congress opted for a
carrot rather than a stick by authorizing a tax credit to incentivize
underground sequestration that mitigates emissions.\79\ With respect to
methane, Congress amended the CAA in 2021 through the Inflation
Reduction Act of 2022 (IRA) to require us to establish a waste
emissions charge for certain sources structured to incentivize
emissions reductions over time.\80\ When addressing GHGs more
generally, Congress has used non-regulatory tools that incentivize,
rather than mandate, changes in private ordering, including through
additional funding provisions in the IRA.\81\ We propose that multiple
instances of recent legislation addressing GHGs individually and
through distinct regulatory approaches suggests that Congress views
such policy decisions as economically and politically significant and
not adequately addressed by general statutory authorities enacted in
response to different problems.
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\78\ Public Law 116-260, Div. S, codified at 42 U.S.C. 7675 et
seq.
\79\ 26 U.S.C. 45Q. In 2020, Congress also instructed us to
recommend improvements to SDWA permitting procedures for injection
wells used in carbon sequestration and appropriated additional
fundings for the ``Class VI'' permitting process. Public Law 116-
260, Div. G, Title II.
\80\ Public Law 117-169, codified at 42 U.S.C. 7436.
\81\ See, e.g., Public Law 117-169, codified at 42 U.S.C. 7432-
7438. We also note that CAA section 211(o)(2)(B)(ii) requires the
EPA to consider ``the impact of the production and use of renewable
fuels on the environment, including on . . . climate change,'' among
many other factors, in setting volumes under the RFS program. 42
U.S.C. 7545(o)(2)(B)(ii).
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The EPA notes that Congress has continued to revise these air
pollutant-specific measures and nonregulatory tools as part of an
ongoing national debate over the appropriate response to global climate
change concerns. On July 4, 2025, President Trump signed into law
significant new legislation enacted by Congress, the One Big Beautiful
Bill Act (OBBB),\82\ which repealed a number of relevant measures
adopted in the IRA and rescinded the EPA's appropriations to carry out
a number of funding programs related to GHG emissions. Among other
things, Congress prohibited the Agency from collecting the waste
emission charge for methane for ten years beyond the original statutory
collection date, rescinded funding to administer grant programs in CAA
sections 132 and 135-38, and repealed CAA section 134, which had
included a section-specific definition of ``greenhouse gas'' applicable
to the grant
[[Page 36307]]
program set out in that section.\83\ We propose that this legislation,
which was the product of substantial national debate and revised and
rescinding funding for provisions of the IRA that were themselves the
product of substantial national debate, indicates that the EPA erred in
attempting to resolve significant policy issues on its own accord in
the Endangerment Finding.
---------------------------------------------------------------------------
\82\ Public Law 119-21.
\83\ 42 U.S.C. 7434(c)(2) (2022).
---------------------------------------------------------------------------
Congress has also recently disapproved several actions taken by the
EPA with respect to GHG emissions. On May 19, 2025, President Trump
signed into law a resolution adopted by Congress under the
Congressional Review Act (CRA) to void our final rule implementing the
waste emission charge added to the CAA in 2021.\84\ And on June 12,
2025, President Trump signed into law three resolutions adopted by
Congress under the CRA to void waivers we granted under CAA section 209
that allowed California and participating States to enforce GHG
emission regulations for motor vehicles and engines, up to and
including zero-emissions standards that mandated a shift to electric
vehicles.\85\ We propose that these disapproval resolutions further
demonstrate the economic and political significance of the EPA's GHG
emission regulations and reinforce the understanding that Congress
intends to reserve such major questions of policy for itself. See West
Virginia, 597 U.S. at 731-32.
---------------------------------------------------------------------------
\84\ Public Law 119-2; see 90 FR 21225 (May 19, 2025).
\85\ H.J. Res. 87; H.J. Res. 88; H.J. Res. 89; see also Diamond
Alt. Energy, LLC v. EPA, No. 24-7, slip op. at 4 n.1 (U.S. June 20,
2025); Statement by the President (June 12, 2025): <a href="https://www.whitehouse.gov/briefings-statements/2025/06/statement-by-the-president/">https://www.whitehouse.gov/briefings-statements/2025/06/statement-by-the-president/</a>.
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Proposed Conclusion. Under our proposal that the major questions
doctrine applies, we propose to conclude that the EPA lacks the ``clear
congressional authorization'' required for the novel approach taken in
the Endangerment Finding and resulting GHG emission standards and must
rescind these actions. West Virginia, 597 U.S. at 723 (quoting UARG,
573 U.S. at 324). We propose that our statutory authority under CAA
section 202(a) to ``prescribe . . . standards'' does not clearly
authorize the EPA to regulate in response to global climate change
concerns or, in issuing such regulations, to mandate a shift from
gasoline-powered vehicles to electric vehicles.
In West Virginia, the Supreme Court held that our authority ``to
establish emission caps at a level reflecting `the application of the
best system of emission reduction . . . adequately demonstrated' '' did
not clearly authorize the EPA to issue emission guidelines that
addressed global climate change concerns by mandating a shift away from
coal-generated electricity. 597 U.S. at 732. Similarly, in UARG, the
Court held that our PSD and Title V authorities could not be extended
to GHG emissions because those provisions ``are designed to apply to,
and cannot rationally be extended beyond, a relative handful of large
sources capable of shouldering heavy substantive and procedural
burdens.'' 573 U.S. at 303.
We propose that these cases control the analysis of our authority
under CAA section 202(a). As in West Virginia, our statutory authority
and the findings required to invoke that authority do not clearly
authorize the approach taken in the Endangerment Finding and subsequent
regulations. And as in UARG, our statutory authority to ``prescribe . .
. standards'' for emissions of certain air pollutants does not clearly
authorize using the CAA's vehicle-emission control scheme to address
global climate change. As discussed above, the Endangerment Finding did
not limit itself to considering the impacts of GHG emissions from new
motor vehicles and engines. Rather, the Endangerment Finding reviewed
the totality of adverse impacts from climate change attributed to all
anthropogenic sources of GHG emissions worldwide and asserted
jurisdiction over CAA section 202(a) sources by finding they
contributed to such impacts by emitting more than de minimis quantities
of GHGs. That understanding has permeated our GHG emission rulemakings
since 2009, and we have attempted to apply that framework to our
distinct regulatory authorities for stationary sources and aircraft.
In Massachusetts, the Supreme Court disagreed with the EPA's
argument that GHGs were not ``air pollutants'' because Congress had not
revisited CAA section 202(a) in amending the CAA in 1990. 549 U.S. at
512-13. The Court found that our reliance on Brown & Williamson to
support that argument was misplaced because unlike the ban on tobacco
products at issue in that case, ``EPA jurisdiction would lead to no
such extreme measures.'' Id. at 531. The Court also found that unlike
the Food and Drug Administration's earlier statements on tobacco
products, ``EPA had never disavowed the authority to regulate
greenhouse gases'' and had issued a memorandum in 1998 suggesting that
we had such authority. Id.
We propose that Massachusetts did not consider or have reason to
interpret the scope of the EPA's authority under CAA section 202(a)
given our position in the 2003 Denial that GHGs are not ``air
pollutant[s]'' under any provision of the statute. Rather, we propose
Massachusetts rejected our position that GHGs are ``categorically''
excluded from the CAA and remanded for the Administrator to determine
whether four GHGs met the standard in CAA section 202(a). UARG, 573
U.S. at 320. We further propose that Massachusetts must be read
together with the Supreme Court's decisions in West Virginia and UARG,
which applied the major questions doctrine to statutory provisions
similar to CAA section 202(a). To that end, we seek comment on whether
Massachusetts applied the major questions doctrine in the first
instance,\86\ and, if it did, whether that analysis informs the meaning
of CAA section 202(a) on its own terms and in light of UARG and West
Virginia. Finally, we propose that the EPA's course of rulemaking has
not been limited to emission standards as anticipated in Massachusetts.
We seek comment on whether a new major questions doctrine analysis is
required because the EPA's rulemakings in response to the Endangerment
Finding have included electric vehicle mandates that require shifting
the national vehicle fleet from one type of vehicle and vehicle fuel to
another.
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\86\ We note that recent Supreme Court decisions have not cited
Massachusetts as a precedent applying, or declining to apply, the
major questions doctrine. See, e.g., Nebraska, 600 U.S. 477; West
Virginia, 597 U.S. 697.
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B. Alternative Rationale for Proposed Rescission
In the alternative, the EPA proposes that even if CAA section
202(a) could be read to authorize prescribing GHG emission standards
for new motor vehicles and engines, the Endangerment Finding
unreasonably applied the statutory standard for regulation to the
scientific record and should be rescinded on that basis. This
subsection proposes several reasons that the Administrator would
exercise his discretionary judgment differently today in light of
intervening legal and scientific developments that appear to undermine
the assumptions, methodologies, and conclusions of the Endangerment
Finding.
1. Climate Science Discussion
The Administrator reviewed available information, including the
most recently available scientific information, bearing on the
assumptions and conclusions in
[[Page 36308]]
the Endangerment Finding, the impacts of global GHG concentrations on
public health and welfare in the United States, and the relative
contribution of domestic emissions from new motor vehicles and engines
to global GHG concentrations. As previously explained, this review
included the 2025 CWG Draft Report, which analyzes empirical data,
peer-reviewed studies, and available scientific information bearing on
direct human influence on ecosystems and climate, climate response to
CO<INF>2</INF> emissions, and impacts on ecosystems and society.\87\
The Administrator also considered available assessments by the U.S.
Government and relevant international bodies, including the Third,
Fourth, and Fifth NCAs reported by the USGCRP and AR5 and AR6 by the
United Nations IPCC. The Administrator also considered critiques of the
NCAs, and the Fifth NCA in particular, and reviewed these analyses for
consistency with OMB information quality guidelines \88\ and the
transparency and reliability requirements of Executive Order 14303,
``Restoring Gold Standard Science.'' \89\
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\87\ As stated earlier, the 2025 CWG Draft Report was provided
to the EPA on May 27, 2025, and was reviewed and relied upon in
formulating this proposal. The EPA understands that DOE is releasing
an updated version of the CWG draft report and seeking public
comment on the updated report, which includes additional information
and typographical corrections that the EPA did not rely upon in
formulating this proposal. Interested parties may review and comment
on the updated version of the CWG draft report for consideration as
part of DOE's efforts at <a href="https://www.energy.gov/topics/climate">https://www.energy.gov/topics/climate</a>.
\88\ 67 FR 8452 (Feb. 22, 2002).
\89\ Executive Order 14303, 90 FR 22601 (May 29, 2025).
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The Endangerment Finding itself acknowledged significant
uncertainties related to climate change and its potential impacts when
it stated that the ``inherent uncertainty in the direction, magnitude
and/or rate of certain future climate change impacts opens up the
possibility that some changes could be more or less than expected, and
the possibility of unanticipated outcomes.'' 74 FR 66524. Specifically,
the Endangerment Finding identified uncertainties including, but not
limited to: the net health impacts of a temperature increase due to
decreases in cold-related mortality, 74 FR 66497, 66526; increases in
allergenic illnesses and pathogen borne disease vectors, 74 FR 66498;
food production and crop yields, including the scope of potential
beneficial impacts from climate change, 74 FR 66498, 66535; temperature
at the end of the 21st Century, 74 FR 66519; records of temperature
before 1600 A.D., 74 FR 66523; estimates and future projections of
anthropogenic aerosols and their respective heating or cooling effects,
74 FR 66519; the extent to which human-induced climate change affects
the intensity and frequency of extreme weather events, 74 FR 66531; and
emissions from future fleet motor vehicles, which could be impacted by
a number of technological, economic, and independent regulatory
factors, 74 FR 66543.
With respect to projected increases in GHG concentrations and
global temperatures, the projections relied upon in the Endangerment
Finding appear unduly pessimistic in light of empirical observations
made after it was finalized in 2009 through 2024. The Endangerment
Finding relied primarily on IPCC AR4 to predict global temperature
increases between 1.8 and 4 degrees Celsius by 2100, an extremely wide
and variable range that necessarily impacts the existence, extent, and
severity of anticipated dangers to public health and welfare. 74 FR
66519. However, as previously noted, IPCC scenarios depicting worst-
case, ``business as usual'' assessments have been criticized as
misleading (2025 CWG Draft Report at 16),\90\ and empirical data
suggest that actual GHG emission concentration increase and
corresponding warming trends through 2025 have tracked the IPCC's more
optimistic scenarios (2025 CWG Draft Report at 18).\91\ Recent
scientific analyses propose that this divergence may be explained by
greater capacity for the climate to reuptake GHGs in the atmosphere
through natural processes. Terrestrial ecosystems have demonstrated a
greater than anticipated sensitivity to elevated CO<INF>2</INF>
concentrations in the form of enhanced plant growth, which results in
greater removal of CO<INF>2</INF> from the atmosphere as plants take up
CO<INF>2</INF> and return it to the soil through natural life cycles.
Similarly, the oceans have demonstrated a greater capacity to take up
and process CO<INF>2</INF> (including through aquatic plant life)
without resulting in the anticipated negative impacts on pH and ocean
ecosystems, including coral reefs (2025 CWG Draft Report at 6-9, 18-
20).\92\
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\90\ See also Hausfather, Z. & Peters, G.P. (2020). Emissions--
the `business as usual' story is misleading. Nature, 577, 618-620:
<a href="https://doi.org/10.1038/d41586-020-00177-3">https://doi.org/10.1038/d41586-020-00177-3</a>; Burgess, M.G. et al.
(2021). IPCC baseline scenarios have over-projected CO<INF>2</INF>
emissions and economic growth. Environmental Research Letters, 16,
014016: <a href="https://doi.org/10.1088/1748-9326/abcdd2">https://doi.org/10.1088/1748-9326/abcdd2</a>; Pielke, R., &
Ritchie, J. (2020). Systemic Misuse of Scenarios in Climate Research
and Assessment Social Sciences Research Network. SSRN: <a href="http://doi.org/10.2139/ssrn.3581777">http://doi.org/10.2139/ssrn.3581777</a>.
\91\ See also Hausfather, Z. et al. (2019). Evaluating the
Performance of Past Climate Model Projections. Geophysical Research
Letters, 47(1): <a href="https://doi.org/10.1029/2019GL085378">https://doi.org/10.1029/2019GL085378</a>; Scaffeta, N.
(2023). CMIP6 GCM ensemble members versus global surface
temperatures. Climate Dynamics, 60, 3091-3120: <a href="https://doi.org/10.1007/s00382-022-06493-w">https://doi.org/10.1007/s00382-022-06493-w</a>; McKitrick, R. & Christy, J. (2020).
Pervasive Warming Bias in CMIP6 Tropospheric Layers. Earth and Space
Science, 7(9), e2020EA001281: <a href="https://doi.org/10.1029/2020EA001281">https://doi.org/10.1029/2020EA001281</a>;
Karl, T.R. et al. (2006). Temperature Trends in the Lower
Atmosphere: Steps for Understanding and Reconciling Differences.
U.S. Climate Change Science Program, Subcommittee on Global Change
Research.
\92\ See also Browman, H.I. (2016). Applying organized
scepticism to ocean acidification research. ICES Journal of Marine
Science, 73(3), 529.1-536: <a href="https://doi.org/10.1093/icesjms/fsw010">https://doi.org/10.1093/icesjms/fsw010</a>;
Clements, J.C. et al. (2022). Meta-analysis reveals an extreme
``decline effect'' in the impacts of ocean acidification on fish
behavior. PLOS Biology, 20(2), e3001511: <a href="https://doi.org/10.1371/journal.pbio.3001511">https://doi.org/10.1371/journal.pbio.3001511</a>; Friedlingstein, P. et al. (2024). Global
Carbon Budget 2024. Earth System Science Data, 14(4): <a href="https://essd.copernicus.org/preprints/essd-2024-519">https://essd.copernicus.org/preprints/essd-2024-519</a>; Haverd, V. et al.
(2020). Higher than expected CO<INF>2</INF> fertilization inferred
from leaf to global observations. Global Change Biology, 26, 2390-
2402: <a href="https://doi.org/10.1111/gcb.14950">https://doi.org/10.1111/gcb.14950</a>; Zeng, Z. et al. (2017).
Climate mitigation from vegetation biophysical feedbacks during the
past three decades. Nature Climate Change, 7, 432-436: <a href="https://doi.org/10.1038/nclimate3299">https://doi.org/10.1038/nclimate3299</a>.
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Relatedly, recent empirical data and analyses suggest that the
Endangerment Finding was unduly pessimistic in attributing health risks
from heat waves to increases in global temperature. Notwithstanding
increased public attention to heat waves, the data suggest that
domestic temperatures peaked in the 1930s and have remained more or
less stable, in relative terms, since those highs (2025 CWG Draft
Report at 57-60). Moreover, increased urbanization trends contribute to
localized changes in temperature, including because an urban footprint
traps heat and frustrates natural heat-cycling capacity at a localized
and low-atmospheric level (2025 CWG Draft Report at 21-22). Contrary to
the Endangerment Finding's assumptions, data continue to suggest that
mortality risk from cold temperatures remains by far the greater threat
to public health in the United States and around the world at the
aggregate level (2025 CWG Draft Report at 112).\93\ Although the risk
of heat waves featured prominently in the Endangerment Finding, the
Administrator acknowledged at the time that significant uncertainties
existed about the relative benefits and risks in the United States, and
the data since 2009 suggest that the balance of climate change as a
whole appears to skew
[[Page 36309]]
substantially more than previously recognized by the EPA in the
direction of net benefits, or is at least too uncertain to establish a
credible and reliable finding of actionable risk, as discussed further
below.
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\93\ See also Zhao, Q. et al. (2021). Global, regional, and
national burden of mortality associated with non-optimal ambient
temperatures from 2000 to 2019: a three-stage modelling study. The
Lancet Planetary Health, 5(7): <a href="https://doi.org/10.1016/s2542-5196">https://doi.org/10.1016/s2542-5196</a>(21)00081-4; Gasparini, A. et al. (2015). Mortality risk
attributable to high and low ambient temperature: a multicounty
observational study. The Lancet, 386(9991), 369-375: <a href="https://doi.org/10.1016/S0140-6736">https://doi.org/10.1016/S0140-6736</a>(14)62114-0.
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With respect to extreme weather events, the Endangerment Finding
projected adverse health impacts from increased frequency and severity
of hurricanes, flooding, and wildfires. E.g., 74 FR 66498. Recent data
and analyses suggest, however, that despite increased public attention
and concern, such extreme weather events have not demonstrably
increased relative to historical highs (2025 CWG Draft Report at 65-72,
111).\94\ In reviewing the assumptions and conclusions regarding
extreme weather events in the Endangerment Finding, the empirical bases
asserted appear to be more generalized and unsupported than previously
believed and no longer inspire the same degree of confidence. The
Administrator further notes that the risks anticipated in the
Endangerment Finding resulted, in part, from the Agency's decision at
the time to categorically exclude consideration of adaptation and
mitigation that should have been incorporated into the analysis as
credible and relevant information. We propose that the data on weather
events, coupled with the Agency's decision to exclude mitigation and
adaptation information from the analysis, fatally undermines the
Endangerment Finding's conclusions in this respect.
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\94\ See also Masson-Delmotte, V. et al. (2021) Climate Change
2021: The Physical Science Basis. Contribution of Working Group I to
the Sixth Assessment Report of the Intergovernmental Panel on
Climate Change. Cambridge University Press: <a href="https://doi.org/10.1017/9781009157896">https://doi.org/10.1017/9781009157896</a>; Klotzbach, P.J. et al. (2018). Continental U.S.
Hurricane Landfall Frequency and Associated Damage: Observations and
Future Risks. Bulletin of the American Meteorological Society,
99(7), 1359-1376: <a href="https://doi.org/10.1175/BAMS-D-17-0184.1">https://doi.org/10.1175/BAMS-D-17-0184.1</a>;
Hodgkins, G.A. et al. (2017). Climate-driven variability in the
occurrence of major floods across North America and Europe. Journal
of Hydrology, 552, 704-717: <a href="https://doi.org/10.1016/j.jhydrol.2017.07.027">https://doi.org/10.1016/j.jhydrol.2017.07.027</a>; Wuebbles, D.J. et al. (2017). Climate Science
Special Report: Fourth National Climate Assessment, Volume I. U.S.
Global Change Research Program: <a href="http://doi.org/10.7930/J0J964J6">http://doi.org/10.7930/J0J964J6</a>;
Hodgkins, G.A. et al. (2017). Climate-driven variability in the
occurrence of major floods across North America and Europe. Journal
of Hydrology, 552, 704-717: <a href="https://doi.org/10.1016/j.jhydrol.2017.07.027">https://doi.org/10.1016/j.jhydrol.2017.07.027</a>: <a href="https://doi.org/10.1016/j.jhydrol.2017.07.027">https://doi.org/10.1016/j.jhydrol.2017.07.027</a>.
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The Endangerment Finding also identified public health and welfare
impacts from projected increases in sea level and related weather and
climactic events. However, on this issue, too, recent data and analyses
suggest that aggregate sea level rise has been minimal, at least with
respect to impacts on the United States, and that sea level has risen
in some domestic localities while falling in others (2025 CWG Draft
Report at 75-80). The Administrator also questions whether it was
appropriate for the Endangerment Finding to exclude any analysis of
adaptation with respect to sea level rise in particular. Population
growth, infrastructure development, and local and regional planning
decisions have been dynamic in coastal areas since 2009, with different
trends in different coastal areas and different choices made
independently of the EPA's regulatory actions by state and local
governments and private entities. The lack of analysis of adaptation
generally, and particularly with respect to sea level rise, reduces
confidence in the reasonableness, accuracy, and reliability of the
assumptions and conclusions in the Endangerment Finding.
The difficulties with parsing the scientific record continue, and
they go to the root of what methodologies should be given most credence
in making any scientific determinations. The Endangerment Finding
consistently cites climate models as showing or predicting warming
trends, melting ice, anthropogenic droughts, shrinking snowpack, damage
to aquatic systems of life, and increased ocean temperature and
acidity. E.g., 74 FR 66523, 66532. However, the data relied upon as
inputs to these models may be based on inaccurate assumptions. (2025
CWG Draft Report at 14-22).\95\ To name but a few instances: the
Northern hemispheric winter snow cover has not decreased in line with
the models used in the Endangerment Finding; aquatic life is largely
adapted for and has undergone oceanic pH changes throughout the Earth's
history, and the data used by the Endangerment Findings and predictions
of coral decline has not been supported by empirical data showing an
unexpected growth in coral reef ecosystems (2025 CWG Draft Report at 7-
12, 40-41).\96\ In addition, the models relied upon by the Endangerment
Finding may be incorrect with regard to warming in the U.S. Corn Belt
given the divergence of recent empirical data from projected trends
(2025 CWG Draft Report at 32-47).
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\95\ See also McKitrick, R. et al. (2012). Long-Term Forecasting
of Global Carbon Dioxide Emissions: Reducing Uncertainties Using a
Per Capita Approach. Journal of Forecasting, 32(5), 435-451: <a href="https://doi.org/10.1002/for.2248">https://doi.org/10.1002/for.2248</a>.
\96\ See also Connolly, R. et al. (2019). Northern Hemisphere
Snow-Cover Trends (1967-2018): A Comparison between Climate Models
and Observations. Geosciences, 9(3), 135: <a href="https://doi.org/10.3390/geosciences9030135">https://doi.org/10.3390/geosciences9030135</a>; Annual Summary Report of Coral Reef Condition
2021/22. Continued coral recovery leads to 36-year highs across two-
thirds of the Great Barrier Reef. (2022). Australian Institute of
Marine Science: <a href="https://www.aims.gov.au/monitoring-great-barrier-reef/gbr-condition-summary-2021-22">https://www.aims.gov.au/monitoring-great-barrier-reef/gbr-condition-summary-2021-22</a>.
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The Administrator is also troubled by the Endangerment Finding's
seemingly inconsistent treatment of the nature and extent of the role
human action with respect to climate change. The Endangerment Finding
attributes the entirety of adverse impacts from climate change to
increased GHG concentrations, and it attributes virtually the entirety
of increased GHG concentrations to anthropogenic emissions from all
sources. But the causal role of anthropogenic emissions is not the
exclusive source of these phenomena, and any projections and
conclusions bearing on the issue should be appropriately discounted to
reflect additional factors. Moreover, recent data and analyses suggest
that attributing adverse impacts from climate change to anthropogenic
emissions in a reliable manner is more difficult than previously
believed and demand additional analysis of the role of natural factors
and other anthropogenic factors such as urbanization and localized
population growth (2025 CWG Draft Report at 14-22, 82-92).\97\
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\97\ McKitrick, R. (2013). Encompassing tests of socioeconomic
signals in surface climate data. Climatic Change, 120(1-2), 95-107:
<a href="https://doi.org/10.1007/s10584-013-0793-5">https://doi.org/10.1007/s10584-013-0793-5</a>; McKitrick, R. &
Nierenberg, N. (2010). Socioeconomic Patterns in Climate Data.
Journal of Economic and Social Measurement, 35(3-4), 149-175:
<a href="https://doi.org/10.3233/JEM-2010-0336">https://doi.org/10.3233/JEM-2010-0336</a>; McKitrick, R. (2021).
Checking for model consistency in optimal fingerprinting: a comment.
Climate Dynamics, 58(1-2), 405-411: <a href="https://doi.org/10.1007/s00382-021-05913-7">https://doi.org/10.1007/s00382-021-05913-7</a>; McKitrick, R. (2023). Total least squares bias in
climate fingerprinting regressions with heterogeneous noise
variances and correlated explanatory variables. Environmetrics,
35(2), e2835: <a href="https://doi.org/10.1002/env.2835">https://doi.org/10.1002/env.2835</a>; McKitrick, R.
(2022). On the choice of TLS versus OLS in climate signal detection
regression. Climate Dynamics, 60, 359-374: <a href="https://doi.org/10.1007/s00382-022-06315-z">https://doi.org/10.1007/s00382-022-06315-z</a>; Connolly, R. et al. (2021). How much has the sun
influenced Northern Hemisphere temperature trends? An ongoing
debate. Research in Astronomy and Astrophysics, 21(6), 131: <a href="https://doi.org/10.1088/1674-4527/21/6/131">https://doi.org/10.1088/1674-4527/21/6/131</a>.
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In addition, and as noted in particular contexts above, the
Administrator is concerned that the Endangerment Finding did not
adequately balance the projected adverse impacts attributed to global
climate change with the potential benefits to the United States of
increased GHG concentrations, and increased CO<INF>2</INF>
concentrations in particular. Unlike virtually every other gas
regulated under the CAA, CO<INF>2</INF> is necessary for human, animal,
and plant life, and advances public health and welfare by directly
impacting plant growth and therefore the price and availability of
food, the success of American agricultural and related
[[Page 36310]]
industries, and the traditional capacity of the United States to export
significant food supplies around the world for economic and
humanitarian purposes. Recent data and analysis show that even marginal
increases in CO<INF>2</INF> concentrations have substantial beneficial
impacts on plant growth and agricultural productivity, and that this
benefit has been significantly greater than previously believed (2025
CWG Draft Report at 6-7, 104-09).
The Administrator also questions the decision in the Endangerment
Finding to consider together all six ``well-mixed'' GHGs rather than
analyzing the properties and impacts of each on an individual basis. 74
FR 66537. As noted in the 2008 ANPRM, new motor vehicle and engine
emissions of the four GHGs they actually emit have fluctuated and
diverged over time, and each has different interactions with the
climate and natural environment. Nevertheless, the Endangerment Finding
did not undertake individual analyses of these four GHGs and, in fact,
aggregated them together along with two additional GHGs not emitted by
motor vehicles or motor vehicle engines, thereby undermining the
transparency, reliability, and usefulness of the findings. We propose
that each of the collectively treated GHGs demonstrates different
chemical properties, exhibits different interactions with the natural
environment, and present different emissions profiles. The Agency did
not analyze, for example, whether the three GHGs other than
CO<INF>2</INF> emitted by new motor vehicles and engines could be
addressed separately in a manner that would impact the ultimate
conclusions of endangerment and contribution. Nor did the Agency
analyze whether HFCs, which are emitted not by engines but by air
conditioning units, could be addressed separately under CAA section
202(a) or another authority in a manner that would impact the ultimate
conclusions of endangerment and contribution.
Finally, the Administrator notes that the analyses relied upon in
the Endangerment Finding, including the assessment reports of the IPCC
and USGCRP that were available at the time and the subsequent
iterations of those reports that have been published since 2009, have
been criticized on process and quality grounds. Recently, several
public watchdog organizations have raised concerns related to the
process and quality of the Fifth NCA, which shares the underlying
assumptions and conclusions of prior NCAs and IPCC reports. The groups
state that NCA5 does not meet the requirements under Executive Order
14303 and deviated from OMB guidelines on quality, objectivity,
utility, and integrity of information disseminated by Federal agencies.
The Administrator takes each of these concerns seriously and seeks
public comment on the validity of these concerns and how they should be
taken into account when determining whether to finalize any of the
alternatives proposed in this action.
2. Proposed Conclusions
Based on this review of the Endangerment Finding and the most
recently available scientific information, data, and studies, the
Administrator proposes to find, in an exercise in discretionary
judgment, that there is insufficient reliable information to retain the
conclusion that GHG emissions from new motor vehicles and engines in
the United States cause or contribute to endangerment to public health
and welfare in the form of global climate change. This proposed
conclusion is animated both by the Administrator's commitment to
analyzing the statutory standard as a cohesive whole and by the
scientific record, which includes too many analytical gaps,
uncertainties, and speculative predictions to reach an affirmative
endangerment finding and promulgate corresponding emission standards
based on such a finding.
As explained above, the Administrator previously asserted in the
Endangerment Finding that CAA section 202(a) grants ``procedural
discretion'' to sever the findings that trigger regulation from
consideration of the resulting regulations and to sever the
endangerment analysis from the causation or contribution analysis. We
propose that the Administrator would now exercise such discretion
differently to ensure greater reliability, transparency, and public
accountability in the EPA's invocation of regulatory authority. We note
that as a result of the approach taken in the Endangerment Finding, the
Administrator's conclusions with respect to new motor vehicles and
engines were never subject to SAB review as required by the CAA, and
that the public never had the opportunity to participate in a
rulemaking that paired the consideration of risk with discussion of the
regulatory response, including the effectiveness and cost of potential
regulatory approaches. We propose that CAA section 202(a) operates as
an integrated whole, and that the EPA's administration of that
provision should reflect a reasoned consideration of all relevant
factors that is not artificially severed into distinct findings and
rulemakings across time.
In addition, we propose that even if intervening legal developments
have not foreclosed the regulation of GHG emissions from new motor
vehicles and engines under CAA section 202(a), they provide a
reasonable basis for the Administrator to approach the inquiry with
greater caution today than was applied in the Endangerment Finding. At
a minimum, Loper Bright confirms that the EPA can no longer rely on
statutory silence or ambiguity to imply authorities and discretion not
expressly conferred by statute. In exercising the judgment required by
CAA section 202(a), the Administrator would choose to adhere as closely
as possible to the statutory language, prior Agency implementation of
that language, and the initial approach set out in the 2008 ANPRM. We
propose that the Administrator's new approach requires rescinding the
Endangerment Finding as fundamentally inconsistent with the framework
set out in this proposed alternative.
Moreover, we propose that the Administrator would not now find, in
light of the ongoing uncertainties in relevant scientific data and
analyses bearing on the question, that the evidence is sufficiently
reliable to determine that GHG emissions from new motor vehicles and
engines meet the standard for regulation in CAA section 202(a). As
discussed in the preamble, the Administrator reviewed the scientific
record as part of the reconsideration process and no longer has the
degree of confidence previously expressed in the analyses relied upon
in the Endangerment Finding, the attribution decisions made in the
Endangerment Finding, and the balance of projected adverse impacts and
beneficial impacts of climate change struck in the Endangerment
Finding.
The EPA seeks comment, for the first time since the 2009
Endangerment Finding was proposed, on whether, due to new scientific
information and developments since the 2009 Endangerment Finding, there
is a strong enough scientific record to support an affirmative finding
that GHG emissions from section 202(a) sources cause or contribute to
air pollution which may reasonably be anticipated to endanger public
health or welfare. Prompt action is needed to address these concerns,
and the Administrator looks forward to stakeholder input on the
continuing vitality of the assumptions, predictions, and conclusions
animating the 2009 Endangerment Finding.
Additionally, the EPA seeks comment on, if the EPA were to make
such a
[[Page 36311]]
finding, whether a new comment period would be required and what
information would be necessary to provide such a finding. To aid in the
EPA's decision making, we also seek comment on the breadth of the
Administrator's discretion to exercise judgment by rejecting the
approach taken in the Endangerment Finding and the results of adopting
a different approach. We also seek comment on any additional aspects of
the Endangerment Finding that may have fallen short of the
administrative law requirement that agency action be reasonable and
reasonably explained. Conversely, we seek comment on why the approach
taken in the Endangerment Finding remains reasonable given the legal
and scientific developments discussed in this proposal, and the impact,
if any, of the EPA's denial of rulemaking petitions in 2022 and 2010 on
this alternative proposal. As previously noted, we are also seeking
comment on whether the denials in 2022 and 2010 were unlawful for any
additional reasons not explored explicitly in this proposal.
V. Separate Bases for Proposed Repeal of GHG Emission Standards
In this section, the EPA proposes repealing existing GHG emission
standards for reasons unrelated to the decision to rescind or retain
the Endangerment Finding. CAA section 202(a) requires us to consider
additional factors before emission standards issued in response to an
endangerment finding may go into effect, including cost, the useful
life of the vehicles or engines, and the availability of ``requisite
technology.'' \98\ Consistent with the language and structure of the
statute and the Supreme Court's express reservation of this question in
Massachusetts, we propose to conclude that policy considerations may be
taken into account, at a minimum, when setting standards in response to
an endangerment finding or, as here, when determining whether to
maintain standards already established.\99\
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\98\ See 42 U.S.C. 7521(a)(1)-(2), (a)(3)(B).
\99\ See Massachusetts, 549 U.S. at 534-35 (``We need not and do
not reach the question whether on remand EPA must make an
endangerment finding, or whether policy concerns can inform EPA's
actions in the event that it makes such a finding.'').
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Specifically, we are proposing that there is no ``requisite
technology'' for emission control for light- and medium-duty vehicles
because reducing GHG emissions from such vehicles to zero would not
measurably impact GHG concentrations in the atmosphere or the rate of
global climate change. Relatedly, we are proposing that there is no
``requisite technology'' for emission control for heavy-duty vehicles
and engines, even if considered in combination with light- and medium-
duty vehicle standards. Finally, we are proposing that GHG emission
standards may harm, rather than advance, public welfare as defined in
the CAA by reducing fleet turnover that improves air quality, safety,
consumer choice, and economic opportunity.
Each of these proposals would, if finalized, serve as an
independent and sufficient basis for repealing the relevant GHG
emission standards as proposed in section VI of this preamble. The EPA
seeks comment on all aspects of these alternative proposed bases for
repeal of the GHG emission standards as indicated in the remainder of
this section.
A. There Is No Requisite Technology for Light- and Medium-Duty Vehicles
That Meaningfully Addresses the Identified Dangers of the Six ``Well-
Mixed'' GHGs
The EPA proposes to repeal GHG emission standards for light- and
medium-duty vehicles because no technology for this source category is
capable of preventing or controlling the ``air pollution'' identified
as a danger to public health and welfare in the Endangerment Finding,
i.e., global concentrations of GHGs in the upper atmosphere. CAA
section 202(a)(1) provides that new motor vehicles and engines may
comply with emission standards ``as complete systems'' or by
``incorporat[ing] devices to prevent or control'' the air pollution
that endangers public health or welfare.\100\ CAA section 202(a)(2)
further provides that emission standards cannot go into effect until
``after such period as the Administrator finds necessary to permit the
development and application of the requisite technology, giving
appropriate consideration to the cost of compliance within such
period.'' \101\
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\100\ 42 U.S.C. 7521(a)(1).
\101\ 42 U.S.C. 7521(a)(2).
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As noted elsewhere in this preamble, GHG emissions from the United
States were 11 percent of global GHG emissions in 2022,\102\ down from
23.5 percent in 2005.\103\ The U.S. transportation sector accounted for
28 percent of domestic GHG emissions in 2022, and light- and medium-
duty vehicles accounted for 57 percent of U.S. transportation sector
GHG emissions.\104\ Taken together, the best available data indicate
that GHG emissions from light- and medium-duty vehicles in the United
States amounted to approximately 1.8 percent of global GHG emissions in
2022. Reducing GHG emissions from light- and medium-duty vehicles in
the United States to zero would result in a 1.8 percent decrease in
global GHG emissions, which corresponds to an approximate 3 percent
reduction in predicted warming trends (2025 CWG Draft Report at
130).\105\ To note, these percentages do not account for trends
demonstrating that the United States has been decreasing absolute GHG
emissions while other countries like China are significantly increasing
their GHG emissions.\106\
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\102\ U.S. Environmental Protection Agency. (Last updated Mar.
31, 2025). Global Greenhouse Gas Overview: <a href="https://www.epa.gov/ghgemissions/global-greenhouse-gas-overview">https://www.epa.gov/ghgemissions/global-greenhouse-gas-overview</a>.
\103\ 74 FR 66539.
\104\ U.S. Environmental Protection Agency. (Last updated July
1, 2025). Inventory of U.S. Greenhouse Gas Emissions and Sinks:
<a href="https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks">https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks</a>.
\105\ See also U.S. Transportation Sector Greenhouse Gas
Emissions 1990-2022. (2024). United States Environmental Protection
Agency 89 FR 11275 (Feb. 14, 2024); Statistical Review of World
Energy. (2024). Energy Institute: <a href="https://www.energyinst.org/statistical-review">https://www.energyinst.org/statistical-review</a>.
\106\ Crippa, M. et al. (2023). GHG emissions of all world
countries. Publications Office of the European Union: <a href="https://doi.org/10.2760/953322">https://doi.org/10.2760/953322</a>.
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Global warming trends from 1979 to 2023, the period with the best
available data, were determined to a precision (or margin of error) of
plus or minus 15 percent total (id.). An estimated 3 percent reduction
in global warming trends is well below the scientific threshold for
measurability and is not a reliable measure for regulatory purposes.
By defining global GHG concentrations in the upper atmosphere as
the relevant threat to public health and welfare in the United States,
the Endangerment Finding identified a problem that the regulatory tools
Congress provided under CAA section 202(a) are simply unable to
meaningfully address. Notably, that action defined the relevant ``air
pollution'' as six ``well-mixed'' GHGs, meaning the combination of GHGs
rather than an individual air pollutant that could be emitted by
certain sources at greater or lesser levels and would be more amenable
to effec
[…truncated; see source link]Indexed from Federal Register on August 1, 2025.
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