[Federal Register Volume 74, Number 78 (Friday, April 24, 2009)]
[Proposed Rules]
[Pages 18886-18910]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-9339]



[[Page 18885]]

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Part III





Environmental Protection Agency





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40 CFR Chapter 1



Proposed Endangerment and Cause or Contribute Findings for Greenhouse 
Gases Under Section 202(a) of the Clean Air Act; Proposed Rule

Federal Register / Vol. 74 , No. 78 / Friday, April 24, 2009 / 
Proposed Rules

[[Page 18886]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Chapter 1

[EPA-HQ-OAR-2009-0171; FRL-8895-5]
RIN 2060-ZA14


Proposed Endangerment and Cause or Contribute Findings for 
Greenhouse Gases Under Section 202(a) of the Clean Air Act

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: Today the Administrator is proposing to find that greenhouse 
gases in the atmosphere endanger the public health and welfare of 
current and future generations. Concentrations of greenhouse gases are 
at unprecedented levels compared to the recent and distant past. These 
high atmospheric levels are the unambiguous result of human emissions, 
and are very likely the cause of the observed increase in average 
temperatures and other climatic changes. The effects of climate change 
observed to date and projected to occur in the future--including but 
not limited to the increased likelihood of more frequent and intense 
heat waves, more wildfires, degraded air quality, more heavy downpours 
and flooding, increased drought, greater sea level rise, more intense 
storms, harm to water resources, harm to agriculture, and harm to 
wildlife and ecosystems--are effects on public health and welfare 
within the meaning of the Clean Air Act. In light of the likelihood 
that greenhouse gases cause these effects, and the magnitude of the 
effects that are occurring and are very likely to occur in the future, 
the Administrator proposes to find that atmospheric concentrations of 
greenhouse gases endanger public health and welfare within the meaning 
of Section 202(a) of the Clean Air Act. She proposes to make this 
finding specifically with respect to six greenhouse gases that together 
constitute the root of the climate change problem: carbon dioxide, 
methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and 
sulfur hexafluoride.
    The Administrator is also proposing to find that the combined 
emissions of carbon dioxide, methane, nitrous oxide, and 
hydrofluorocarbons from new motor vehicles and new motor vehicle 
engines are contributing to this mix of greenhouse gases in the 
atmosphere. Thus, she proposes to find that the emissions of these 
substances from new motor vehicles and new motor vehicle engines are 
contributing to air pollution which is endangering public health and 
welfare under section 202(a) of the Clean Air Act.

DATES: Comments on this proposed action must be received on or before 
June 23, 2009. If you submitted comments on the issues raised by this 
proposal in dockets for other Agency efforts (e.g., the Advance Notice 
of Proposed Rulemaking on Regulating Greenhouse Gases under the Clean 
Air Act), you must still submit your comments to the docket for this 
action (EPA-HQ-OAR-2009-0171) by the deadline if you want them to be 
considered.
    There will be two public hearings. One hearing will be held on May 
18, 2009 in Arlington, VA. The other hearing will be on May 21, 2009 in 
Seattle, WA. To obtain information about the public hearings or to 
register to speak at the hearings, please see the SUPPLEMENTARY 
INFORMATION section below or go to http://www.epa.gov/climatechange/endangerment.html.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2009-0171, by one of the following methods:
     Federal eRulemaking Portal: http://www.regulations.gov. 
Follow the online instructions for submitting comments.
     E-mail: GHG-Endangerment-Docket@epa.gov.
     Fax: (202) 566-1741.
     Mail: Environmental Protection Agency, EPA Docket Center 
(EPA/DC), Mailcode 6102T, Attention Docket ID No. EPA-HQ-OAR-2009-0171, 
1200 Pennsylvania Avenue, NW., Washington, DC 20460.
     Hand Delivery: EPA Docket Center, Public Reading Room, EPA 
West Building, Room 3334, 1301 Constitution Avenue, NW., Washington, DC 
20004. Such deliveries are only accepted during the Docket's normal 
hours of operation, and special arrangements should be made for 
deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2009-0171. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available online at 
http://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be CBI or 
other information whose disclosure is restricted by statute. Do not 
submit information that you consider to be CBI or otherwise protected 
through http://www.regulations.gov or e-mail. The http://www.regulations.gov Web site is an ``anonymous access'' system, which 
means EPA will not know your identity or contact information unless you 
provide it in the body of your comment. If you send an e-mail comment 
directly to EPA without going through http://www.regulations.gov your 
e-mail address will be automatically captured and included as part of 
the comment that is placed in the public docket and made available on 
the Internet. If you submit an electronic comment, EPA recommends that 
you include your name and other contact information in the body of your 
comment and with any disk or CD-ROM you submit. If EPA cannot read your 
comment due to technical difficulties and cannot contact you for 
clarification, EPA may not be able to consider your comment. Electronic 
files should avoid the use of special characters, any form of 
encryption, and be free of any defects or viruses.
    Docket: All documents in the docket are listed in the http://www.regulations.gov index. 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, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at the Air Docket, EPA/
DC, EPA West, Room B102, 1301 Constitution Ave., NW., Washington, DC. 
This Docket Facility is open from 8:30 a.m. to 4:30 p.m., Monday 
through Friday, excluding legal holidays. The telephone number for the 
Public Reading Room is (202) 566-1744, and the telephone number for the 
Air Docket is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT: Jeremy Martinich, Climate Change 
Division, Office of Atmospheric Programs (MC-6207J), Environmental 
Protection Agency, 1200 Pennsylvania Ave., NW., Washington, DC 20460; 
telephone number: (202) 343-9927; fax number: (202) 343-2202; e-mail 
address: ghgendangerment@epa.gov. Please use this contact information 
for general questions only. Official comments must be submitted using 
the instructions above.

SUPPLEMENTARY INFORMATION:
    Additional Information on Public Hearings: The two public hearings 
will be held on May 18 in Arlington, VA, and on May 21, 2009, in 
Seattle, WA. Both hearings will begin at 9 a.m. and end at 8 p.m., 
respective local times.
    Addresses: The hearings will be held at the following locations:

[[Page 18887]]

    1. Arlington, VA: One Potomac Yard, 2777 S. Crystal Drive, 
Arlington, VA 22202.
    2. Seattle, WA: Bell Harbor International Conference Center, 2211 
Alaskan Way, Pier 66, Seattle, WA 98121.
    The public hearings will provide interested parties the opportunity 
to present data, views, or arguments concerning the proposed findings. 
The EPA may ask clarifying questions during the oral presentations, but 
will not respond to the presentations at that time. Written statements 
and supporting information submitted during the comment period will be 
considered with the same weight as any oral comments and supporting 
information presented at the public hearings. Written comments must be 
received by the last day of the comment period, as specified in the 
proposal.
    To obtain additional information about the public hearings or to 
register to speak at the hearings, please go to: http://www.epa.gov/climatechange/endangerment.html. Alternatively, contact Jeremy 
Martinich at 202-343-9927. Verbatim transcripts of the hearings and 
written statements will be included in the rulemaking docket.

What Should I Consider as I Prepare My Comments for EPA?

1. Submitting CBI

    Do not submit this information to EPA through www.regulations.gov 
or e-mail. Clearly mark the part or all of the information that you 
claim to be confidential business information (CBI). For CBI 
information in a disk or CD ROM that you mail to EPA, mark the outside 
of the disk or CD ROM as CBI and then identify electronically within 
the disk or CD ROM the specific information that is claimed as CBI. In 
addition to one complete version of the comment that includes 
information claimed as CBI, a copy of the comment that does not contain 
the information claimed as CBI must be submitted for inclusion in the 
public docket. Information so marked will not be disclosed except in 
accordance with procedures set forth in 40 CFR part 2.

2. Tips for Preparing Your Comments

    When submitting comments, remember to:
     Explain your views as clearly as possible.
     Describe any assumptions that you used.
     Provide any technical information and/or data you used 
that support your views.
     Provide specific examples to illustrate your concerns.
     Offer alternatives.
     Make sure to submit your comments by the comment period 
deadline identified.
     To ensure proper receipt by EPA, identify the appropriate 
docket identification number in the subject line on the first page of 
your response. It would also be helpful if you provided the name, date, 
and Federal Register citation related to your comments.

Table of Contents

I. Introduction
    A. Summary
    B. Background Information Helpful to Understanding This Proposal
    1. Greenhouse Gases and Their Effects
    2. Statutory Basis for This Proposal
    3. The Supreme Court's Decision in Massachusetts v. EPA
    a. The Petition of the International Center for Technology 
Assessment
    b. The Supreme Court's Decision
    4. EPA's Advance Notice of Proposed Rulemaking on Regulating 
Greenhouse Gases Under the Clean Air Act
    C. Solicitation of Comments
II. Legal Framework for This Action
    A. Section 202(a)--Endangerment and Cause or Contribute
    1. The Statutory Language
    2. Origin of the Current Statutory Language
    a. Ethyl Corp. v. EPA
    b. The 1977 Clean Air Act Amendments
    3. Additional Considerations for the Cause or Contribute 
Analysis
    4. Comments on Elements of the Endangerment and Cause or 
Contribute Tests Made During the ANPR Public Comment Period
    B. Air Pollutant, Public Health and Welfare
III. The Administrator's Proposed Endangerment Finding
    A. Approach in Utilizing the Best Available Scientific 
Information
    B. The Air Pollution
    1. Common Features of the Six Key Greenhouse Gases
    2. Evidence That the Six Greenhouse Gases Are at Unprecedented 
Levels in the Atmosphere
    3. Evidence That Elevated Atmospheric Concentrations of the Six 
Greenhouse Gases Are the Root Cause of Observed Climate Change
    4. Other Climate Forcers
    a. Water Vapor
    b. The Ozone-Depleting Substances: CFCs, HCFCs and Halons
    c. Tropospheric Ozone
    d. Black Carbon
    e. Fluorinated Ethers and Recently Identified Greenhouse Gases
    C. The Administrator's Proposed Finding That the Air Pollution 
Endangers Public Health and Welfare
    1. Evidence of Currently Observed Climatic and Related Effects
    2. Future Projected Climatic and Related Effects
    3. Impacts on Public Health
    4. Impacts on Public Welfare
    5. The Administrator's Consideration of International Effects
    6. The Administrator's Consideration of Key Uncertainties
    7. Summary
IV. The Administrator's Cause or Contribute Finding
    A. The Air Pollutant(s)
    1. Proposed Definition of Air Pollutant
    2. How the Definition of Air Pollutant in the Endangerment 
Determination Affects Section 202(a) Standards
    B. Proposed Cause or Contribute Finding
    1. Overview of Greenhouse Gas Emissions
    2. Overview of Section 202(a) Source Categories and Cause or 
Contribute Analysis
    3. Proposed Finding That Emissions of the Collective Group of 
Six Greenhouse Gases Contributes to Air Pollution Which May 
Reasonably Be Anticipated To Endanger Public Health and Welfare
    a. Total Greenhouse Gas Emissions From Section 202(a) Source 
Categories
    b. Proposed Contribution Finding for the Single Air Pollutant 
Comprised of the Collective Group of Six Greenhouse Gases
    4. Additional Consideration of Whether Each Greenhouse Gas as a 
Separate Air Pollutant Contributes to Air Pollution Which May 
Reasonably Be Anticipated To Endanger Public Health and Welfare
    a. Carbon Dioxide Emissions From Section 202(a) Source 
Categories
    b. Methane Emissions From Section 202(a) Source Categories
    c. Nitrous Oxide Emissions From Section 202(a) Source Categories
    d. HFC emissions From Section 202(a) Source Categories
V. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

I. Introduction

A. Summary

    Pursuant to section 202(a) of the Clean Air Act (CAA or Act), the 
Administrator proposes to find that the mix of six key greenhouse gases 
in the atmosphere may reasonably be anticipated to endanger public 
health and welfare. Specifically, the Administrator is proposing to 
define the ``air pollution'' referred to in section

[[Page 18888]]

202(a) of the CAA to be the mix of six key directly emitted and long-
lived greenhouse gases: Carbon dioxide (CO2), methane 
(CH4), nitrous oxide (N2O), hydrofluorocarbons 
(HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride 
(SF6). It is the Administrator's judgment that the total 
body of scientific evidence compellingly supports a positive 
endangerment finding for both public health and welfare. The 
Administrator reached this judgment by considering both observed and 
projected future effects, and by considering the full range of risks 
and impacts to public health and welfare occurring within the U.S., 
which by itself warrants this judgment. In addition, the scientific 
evidence concerning risks and impacts occurring outside the U.S., 
including risks and impacts that can affect people in the U.S., 
provides further support for this finding.\1\
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    \1\ As discussed later, EPA does not need to determine, and is 
not determining, whether impacts occurring outside the U.S. would be 
sufficient by themselves to justify the proposed endangerment 
finding. Instead the impacts occurring outside the U.S. are 
considered as providing additional support for the proposed finding, 
in a situation where, as here, the impacts occurring within the U.S. 
are sufficient on their own to warrant the proposed finding. Thus, 
the Administrator does not now take a position on the legal question 
whether international effects, on their own, would be sufficient to 
support an endangerment finding under the Clean Air Act.
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    Under section 202(a) of the CAA, the Administrator is to determine 
whether emissions of any air pollutant from new motor vehicles and 
their engines cause or contribute to air pollution which may reasonably 
be anticipated to endanger public health or welfare. The Administrator 
further proposes to find that combined emissions from new motor 
vehicles and new motor vehicle engines of four of these greenhouse 
gases--carbon dioxide, methane, nitrous oxide, and hydrofluorocarbons--
contribute to this air pollution. The other greenhouse gases that are 
the subject of this proposal (perfluorocarbons and sulfur hexafluoride) 
are not emitted by motor vehicles.
    The Administrator's proposed findings come in response to the 
Supreme Court's decision in Massachusetts v. EPA, 549 U.S. 497 (2007). 
That case involved a petition submitted by the International Center for 
Technology Assessment and 18 other environmental and renewable energy 
industry organizations requesting that EPA issue standards under 
section 202(a) of the Act for the emissions of carbon dioxide, methane, 
nitrous oxide, and hydrofluorocarbons from new motor vehicles and 
engines. The proposed findings are in response to this petition and are 
for purposes of section 202(a). EPA is not proposing or taking action 
under any other provision of the Clean Air Act.

B. Background Information Helpful to Understanding This Proposal

1. Greenhouse Gases and Their Effects
    Greenhouse gases are gases that effectively trap some of the 
Earth's heat that would otherwise escape to space. Greenhouse gases are 
both naturally occurring and anthropogenic. The primary greenhouse 
gases of concern directly emitted by human activities 
include carbon dioxide, methane, nitrous oxide, 
hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. Of these 
six gases, four (carbon dioxide, methane, nitrous oxide, and 
hydrofluorocarbons) are emitted by motor vehicles.
    These six gases, once emitted, remain in the atmosphere for decades 
to centuries. Thus, they become well mixed globally in the atmosphere 
and their concentrations accumulate when emissions exceed the rate at 
which natural processes remove greenhouse gases from the atmosphere. 
The heating effect caused by the human-induced buildup of greenhouse 
gases in the atmosphere is very likely \2\ the cause of most of the 
observed global warming over the last 50 years. A detailed explanation 
of climate change and its impact on health, society, and the 
environment is included in EPA's technical support document (docket 
OAR-2009-0171) and discussed in the context of the 
Administrator's finding in Section III.
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    \2\ According to Intergovernmental Panel on Climate Change 
(IPCC) terminology, ``very likely'' conveys a 90 to 99 percent 
probability of occurrence. ``Virtually certain'' conveys a greater 
than 99 percent probability, ``likely'' conveys a 66 to 90 percent 
probability, and ``about as likely as not'' conveys a 33 to 66 
percent probability.
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    The U.S. transportation sector is a significant contributor to 
total U.S. and global anthropogenic emissions of greenhouse gases. 
Transportation sources subject to regulation under section 202(a) of 
the Act are the second largest greenhouse gas-emitting sector in the 
U.S., after electricity generation, and accounted for 24 percent of 
total U.S. greenhouse gas emissions in 2006 (see table 1 in section IV 
below) (these emissions are compared on carbon dioxide equivalent 
basis; see footnote 18 for an explanation). Detailed information on 
past, present, and projected greenhouse gas concentrations and 
emissions is provided in the Technical Support Document, and summarized 
in Sections III and IV, respectively.
2. Statutory Basis for This Proposal
    Section 202(a)(1) of the CAA states that ``The Administrator shall 
by regulation prescribe (and from time to time revise) * * * 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 
[her] judgment cause, or contribute to, air pollution which may 
reasonably be anticipated to endanger public health or welfare.''
    Before the Administrator may issue standards addressing emissions 
of greenhouse gases from new motor vehicles or engines under section 
202(a), the Administrator must satisfy a two-step test. First, the 
Administrator must decide whether, in her judgment, the air pollution 
under consideration may reasonably be anticipated to endanger public 
health or welfare. Second, the Administrator must decide whether, in 
her judgment, emissions of an air pollutant from new motor vehicles or 
engines cause or contribute to this air pollution.\3\ If the 
Administrator answers both questions in the affirmative, she must issue 
standards under section 202(a). Massachusetts v. EPA, 549 U.S. at 533.
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    \3\ To clarify the distinction between air pollution and air 
pollutant, the air pollution is the atmospheric concentrations and 
can be thought of as the total, cumulative stock problem of 
greenhouse gases in the atmosphere. The air pollutants, on the other 
hand, are the emissions of greenhouse gases and can be thought of as 
the flow that changes the size of the total stock.
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    Typically, the endangerment and cause or contribute findings have 
been proposed concurrently with proposed standards under various 
sections of the CAA, including section 202(a). Comment has been taken 
on these proposed findings as part of the notice and comment process 
for the emission standards. See, e.g., Rulemaking for non-road 
compression-ignition engines under section 213(a)(4) of the CAA, 
Proposed Rule 58 FR 28809, 28813-14 (May 17, 1993), Final Rule 59 FR 
31306, 31318 (June 17, 1994); Rulemaking for highway heavy duty diesel 
engines and diesel sulfur fuel under sections 202(a) and 211(c) of the 
CAA, Proposed Rule 65 FR 35430 (June 2, 2000), Final Rule 66 FR 5002 
(Jan. 18, 2001). However, there is no requirement that the 
Administrator propose the endangerment and cause or contribute findings 
with proposed standards. The Administrator is moving forward with this 
proposed endangerment finding and a cause or contribute determination

[[Page 18889]]

while developing proposed standards under section 202(a).
    The Administrator is applying the rulemaking provisions of CAA 
section 307(d) to this action.\4\ Thus, these proposed findings will be 
subject to the same rulemaking requirements that would apply if the 
proposed findings were part of the standard-setting rulemaking. Any 
standard setting rulemaking under section 202(a) will also be subject 
to these notice and comment rulemaking procedures.
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    \4\ Commenters on the Advanced Notice of Proposed Rulemaking on 
Regulating Greenhouse Gases under the Clean Air Act, 73 FR 44354 
(2007), see Section I.B.4 below, argued that EPA is required to 
follow notice and comment requirements for the endangerment and 
cause or contribute findings. Without agreeing or disagreeing with 
the reasoning set forth in those comments, the Administrator is 
applying the rulemaking requirements of CAA section 307(d), 
including notice and comment, to today's action. See, e.g., CAA 
sections 307(d)(1)(K) (applying 307(d) requirements to the 
promulgation or revisions of regulations under section 202), 
307(d)(1)(V) (the provisions of section 307(d) apply to ``such other 
actions as the Administrator may determine.'').
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3. The Supreme Court's Decision in Massachusetts v. EPA
a. The Petition of the International Center for Technology Assessment
    On October 20, 1999, the International Center for Technology 
Assessment and 18 other environmental and renewable energy industry 
organizations filed a ``Petition for Rulemaking and Collateral Relief 
Seeking the Regulation of Greenhouse Gas Emissions from New Motor 
Vehicles under Section 202(a) of the Clean Air Act.'' The thrust of the 
petition was that four greenhouse gases--carbon dioxide, methane, 
nitrous oxide, and hydrofluorocarbons--are air pollutants as defined in 
CAA section 302(g), that emissions of these greenhouse gases contribute 
to air pollution which is reasonably anticipated to endanger public 
health or welfare, that these greenhouse gases are emitted by new motor 
vehicles, and therefore that EPA has a mandatory duty to issue 
regulations under CAA section 202(a) addressing these greenhouse gases.
    After an opportunity for public comment, EPA denied the petition in 
a notice issued on August 8, 2003. The Agency concluded that it lacked 
authority under the CAA to regulate greenhouse gases for purposes of 
global climate change, and that even if it did have the authority to 
set greenhouse gas emission standards for new motor vehicles, it would 
be unwise to do so at that time. The federal appeals court in 
Washington, DC, upheld EPA's denial of the petition.
b. The Supreme Court's Decision
    In Massachusetts v. EPA, the Supreme Court reversed the lower 
court's decision and held that EPA had improperly denied the petition. 
549 U.S. 497 (2007). The Court held that greenhouse gases are air 
pollutants under the CAA, and that the alternative grounds EPA gave for 
denying the petition were ``divorced from the statutory text'' and 
hence improper.
    Specifically, the Court held that carbon dioxide, methane, nitrous 
oxide, and hydrofluorocarbons fit the CAA's ``sweeping definition of 
`air pollutant' '' since they are ``without a doubt `physical [and] 
chemical * * * substances which [are] emitted into * * * the ambient 
air.' The statute is unambiguous.'' Id. at 529. The Court also rejected 
the argument that post-enactment legislative developments even 
``remotely suggest[ed] that Congress meant to curtail [EPA's] power to 
treat greenhouse gases as air pollutants.'' Id.
    The Court further rejected the argument that EPA could not regulate 
motor vehicle emissions of the chief greenhouse gas, carbon dioxide, 
because doing so would essentially require control of vehicle fuel 
economy, and Congress delegated that authority to the Department of 
Transportation in the Energy Policy and Conservation Act. The Court 
held that the fact ``that DOT sets mileage standards in no way licenses 
EPA to shirk its environmental responsibilities. EPA has been charged 
with protecting the public's `health' and `welfare,' 42 U.S.C. 
7521(a)(1), a statutory obligation wholly independent of DOT's mandate 
to promote energy efficiency.'' Id. at 532 (citation omitted). The two 
obligations may overlap ``but there is no reason to think the two 
agencies cannot both administer their obligations and yet avoid 
inconsistency.'' Id.
    Turning to EPA's alternative grounds for denial, the Court held 
that EPA's decision on whether or not to grant the petition must relate 
to ``whether an air pollutant `causes, or contributes to, air pollution 
which may reasonably be anticipated to endanger public health or 
welfare.' '' Id. at 532-33. Thus, ``[u]nder the clear terms of the 
Clean Air Act, EPA can avoid taking further action only if it 
determines that greenhouse gases do not contribute to climate change or 
if it provides some reasonable explanation as to why it cannot or will 
not exercise its discretion to determine whether they do.'' Id. at 533. 
The Court held that three of the four reasons EPA advanced as 
alternative grounds for denying the petition were unrelated to whether 
greenhouse gas emissions from new motor vehicles cause or contribute to 
air pollution that may reasonably be anticipated to endanger public 
health or welfare. Thus, EPA had failed to offer a reasoned explanation 
for its action. For example, the Court held that concerns related to 
foreign policy objectives had ``nothing to do with whether greenhouse 
gas emissions contribute to climate change'' and hence could not 
justify the denial. Id. The Court further held that EPA's generalized 
concerns about scientific uncertainty were likewise insufficient unless 
``the scientific uncertainty is so profound that it precludes EPA from 
making a reasoned judgment as to whether greenhouse gases contribute to 
global warming,'' in which case EPA must so find. Id. at 534.
    The Supreme Court was careful to note that it was not dictating 
EPA's action on remand, and was not deciding whether or not EPA must 
find that greenhouse gases endanger public health or welfare. Nor did 
the Court rule on ``whether policy concerns can inform EPA's actions in 
the event that it makes such a finding.'' Id. at 534-35. The Court also 
observed that under CAA section 202(a), ``EPA no doubt has significant 
latitude as to the manner, timing, content, and coordination of its 
regulations with those of other agencies.'' Id. at 533. Nonetheless, 
any EPA decisions concerning the endangerment and cause or contribute 
criteria must be grounded in the requirements of CAA section 202(a).
    Since the Supreme Court's decision in April 2007, some stakeholders 
have taken the position, including in comments on the Advance Notice of 
Proposed Rulemaking discussed below, that the Supreme Court did not 
foreclose EPA's ability to deny the petition without addressing the 
endangerment question. For example, one industry group argued that EPA 
could deny the rulemaking petition based on statutory factors besides 
scientific uncertainty and those already rejected by the Court, but did 
not describe what those additional statutory factors may be or how they 
would support a denial of the ICTA petition.
    EPA does not agree with these interpretations of the Supreme 
Court's decision. Moreover, commenters have not provided examples of 
additional statutory factors that they believe would justify denying 
the petition without addressing the endangerment and cause or 
contribute criteria. Today the Administrator is addressing these 
criteria, and is proposing to find that the mix of six key greenhouse 
gases in the atmosphere may reasonably be anticipated to endanger 
public health

[[Page 18890]]

and welfare due overwhelmingly to the effects of climate change. 
Furthermore, the Administrator is proposing to find that emissions of 
greenhouse gases by motor vehicles collectively contribute to the air 
pollution that endangers public health and welfare.
4. EPA's Advance Notice of Proposed Rulemaking on Regulating Greenhouse 
Gases Under the Clean Air Act
    On July 30, 2008, EPA published an Advance Notice of Proposed 
Rulemaking on ``Regulating Greenhouse Gas Emissions under the Clean Air 
Act'' (73 FR 44354) (ANPR). The ANPR presented information relevant to, 
and solicited public comment on, a wide variety of issues regarding the 
potential regulation of greenhouse gases under the CAA, including EPA's 
response to the Supreme Court's decision in Massachusetts v. EPA. 
Section V of the ANPR contained an earlier version of much of the 
material in this proposal, including the legal framework, a summary of 
the science of climate change, and an illustration of how the 
Administrator could analyze the cause or contribute element using 
information regarding the greenhouse gas emissions of the portion of 
the U.S. transportation sector covered by section 202(a). A July 2008 
version of the Technical Support Document (TSD) for this proposal was 
also in the docket for the ANPR (EPA-HQ-OAR-2008-0318).
    The ANPR also contained a summary of much of the work EPA had done 
in 2007 regarding draft greenhouse gas emission standards for light 
duty vehicles and trucks under section 202(a) of the Act. As noted 
earlier, EPA is currently developing proposed emissions standards 
related to today's proposal. EPA expects that these proposed standards 
will be ready to propose for public comment several months from now.
    Finally, the ANPR also discussed pending petitions under various 
sections of the Act requesting that EPA regulate greenhouse gas 
emissions from other mobile sources, as well as stationary source 
rulemakings (recently completed, ongoing or remanded) in which 
commenters suggested EPA regulate greenhouse gas emissions. EPA is 
continuing to evaluate its response to those other pending petitions 
and rulemakings and will address them in later actions.

C. Solicitation of Comments

    The Administrator requests comments on all aspects of this action. 
She requests comment on the data on which the proposed findings are 
based, the methodology used in obtaining and analyzing the data, and 
the major legal interpretations and policy considerations underlying 
the proposed findings.

II. Legal Framework for This Action

    Two provisions of the CAA govern today's proposal. Section 202(a) 
sets forth a two-part predicate for regulatory action under that 
provision: endangerment and cause or contribute. Section 302 of the Act 
contains definitions of the terms air pollutant and welfare used in 
section 202(a). These statutory provisions are discussed below.

A. Section 202(a)--Endangerment and Cause or Contribute

    As noted above, section 202(a) of the CAA calls for the 
Administrator to exercise her judgment and make two separate 
determinations: first, whether air pollution may reasonably be 
anticipated to endanger public health or welfare, and second whether 
emissions of any air pollutant from new motor vehicles or engines cause 
or contribute to this air pollution.
    Based on the text of this provision and its legislative history, 
the Administrator interprets the two-part test as follows. First, the 
Administrator is required to protect public health and welfare. She is 
not asked to wait until harm has occurred but instead must be ready to 
take regulatory action to prevent harm before it occurs. The 
Administrator is thus to consider both current and future risks. 
Second, the Administrator is to exercise judgment by weighing risks, 
assessing potential harms, and making reasonable projections of future 
trends and possibilities. It follows that when exercising her judgment 
the Administrator balances the likelihood and severity of effects. This 
balance involves a sliding scale; on one end the severity of the 
effects may be significant, but the likelihood low, while on the other 
end the severity may be less significant, but the likelihood high. 
Under either scenario, the Administrator is permitted to find 
endangerment. If the harm would be catastrophic, the Administrator is 
permitted to find endangerment even if the likelihood is small. In the 
context of climate change, for example, the Administrator should take 
account of the most catastrophic scenarios and their probabilities. As 
explained below, however, it is not necessary to rely on low-
probability outcomes in order to find endangerment here.\5\
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    \5\ Cf. Massachusetts v. EPA, 549 U.S. at 525 n.23, citing 
Mountain States Legal Foundation v. Glickman, 92 F.3d 1228, 1234 
(D.C. Cir. 1996) (``The more drastic the injury that government 
action makes more likely, the lesser the increment in probability to 
establish standing''); Village of Elk Grove Village v. Evans, 997 
F.2d 328, 329 (7th Cir. 1993) (``[E]ven a small probability of 
injury is sufficient to create a case or controversy--to take a suit 
out of the category of the hypothetical--provided of course that the 
relief sought would, if granted, reduce the probability.'').
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    Because scientific knowledge is constantly evolving, the 
Administrator may be called upon to make decisions while recognizing 
the uncertainties and limitations of the data or information available, 
as risks to public health or welfare may involve the frontiers of 
scientific or medical knowledge. At the same time, the Administrator 
must exercise reasoned decision making, and avoid speculative or 
crystal ball inquiries. Third, the Administrator is to consider the 
cumulative impact of sources of a pollutant in assessing the risks from 
air pollution, and is not to look only at the risks attributable to a 
single source or class of sources. Fourth, the Administrator is to 
consider the risks to all parts of our population, including those who 
are at greater risk for reasons such as increased susceptibility to 
adverse health effects. If vulnerable subpopulations are especially at 
risk, the Administrator is entitled to take that point into account in 
deciding the question of endangerment. Here too, both likelihood and 
severity of adverse effects are relevant, and here too, catastrophic 
scenarios and their probabilities should be considered. As explained 
below, vulnerable subpopulations face serious health risks as a result 
of climate change.
    This framework recognizes that regulatory agencies such as EPA must 
be able to deal with the reality that ``[m]an's ability to alter his 
environment has developed far more rapidly than his ability to foresee 
with certainty the effects of his alterations.'' See Ethyl Corp v. EPA, 
541 F.2d 1, 6 (D.C. Cir.), cert. denied 426 U.S. 941 (1976). Both ``the 
Clean Air Act `and common sense * * * demand regulatory action to 
prevent harm, even if the regulator is less than certain that harm is 
otherwise inevitable.' '' See Massachusetts v. EPA, 549 U.S. at 506, 
n.7 (citing Ethyl Corp.). To be sure, the concept of ``expected value'' 
has its limitations in this context, but it is useful insofar as it 
suggests that when severe risks to the public health and welfare are 
involved, the Administrator need not wait as evidence continues to 
accumulate.
    The Administrator recognizes that the context for this action is 
unique. There is a very large and comprehensive base of scientific 
information that has been

[[Page 18891]]

developed over many years through a global consensus process involving 
numerous scientists from many countries and representing many 
disciplines. She also recognizes that there are varying degrees of 
uncertainty across many of these scientific issues. It is in this 
context that she is exercising her judgment and applying the statutory 
framework. Further discussion of the language in section 202(a) and its 
legislative history is provided below, to explain more fully the basis 
for this interpretation.
1. The Statutory Language
    The interpretation described above flows from the statutory 
language itself. The phrase ``may reasonably be anticipated'' and the 
term ``endanger'' authorize, if not require, the Administrator to act 
to prevent harm and to act in conditions of uncertainty. They do not 
limit her to merely reacting to harm or to acting only when certainty 
has been achieved; indeed, the references to anticipation and to 
endangerment imply that to fail to look to the future or to less than 
certain risks would be to abjure the Administrator's statutory 
responsibilities. Moreover, by instructing the Administrator to 
consider whether emissions of an air pollutant cause or contribute to 
air pollution, the statute is clear that she need not find that 
emissions from any one sector or group of sources are the sole or even 
the major part of an air pollution problem. The use of the term 
contribute clearly indicates that a lower threshold than a finding that 
such emissions are the sole or major cause is a sufficient basis to 
make the required finding. Finally, the phrase ``in [her] judgment'' 
authorizes the Administrator to weigh risks and to consider projections 
of future possibilities, while also recognizing uncertainties and 
extrapolating from existing data. When exercising her judgment the 
Administrator balances the likelihood and severity of effects. Notably, 
the phrase ``in [her] judgment'' modifies both ``may reasonably be 
anticipated'' and ``cause or contribute.''
2. Origin of the Current Statutory Language
    When Congress revised section 202(a) and other provisions of the 
CAA as part of the 1977 amendments to the CAA, it was responding to an 
opinion issued by the D.C. Circuit regarding the pre-1977 version of 
section 211(c) of the Act. The legislative history of those amendments, 
particularly the report by the House Committee on Interstate and 
Foreign Commerce, demonstrate that EPA's interpretation is fully 
consistent with Congress' intention in crafting this a provision See 
H.R. Rep. 95-294 (1977), as reprinted in 4 A Legislative History of the 
Clean Air Act Amendments of 1977 (1978) at 2465 (hereinafter ``LH'').
a. Ethyl Corp. v. EPA
    In revising the statutory language, Congress relied heavily on the 
en banc decision in Ethyl Corp. v. EPA, which reversed a 3-judge panel 
opinion regarding an EPA rule restricting the content of lead in leaded 
gasoline.\6\ After reviewing the relevant facts and law, the full court 
evaluated the statutory language at issue to see what level of 
``certainty [was] required by the Clean Air Act before EPA may act.'' 
Id. at 7.
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    \6\ At the time of the 1973 rules requiring the reduction of 
lead in leaded gasoline, section 211(c)(1)(A) of the CAA stated that 
the Administrator may promulgate regulations that: ``control or 
prohibit the manufacture, introduction into commerce, offering for 
sale, or sale of any fuel or fuel additive for use in a motor 
vehicle or motor vehicle engine (A) if any emissions product of such 
fuel or fuel additive will endanger the public health or welfare * * 
* .'' CAA 211(c)(1)(A) (1970) (emphasis added). The italicized 
language in the above quote is the relevant language revised by the 
1977 amendments.
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    The petitioners argued that the statutory language ``will 
endanger'' required proof of actual harm, and that the actual harm had 
to come from emissions from the fuels in and of themselves. Id. at 12, 
29. The en banc court rejected this approach, finding that the term 
``endanger'' allowed the Administrator to act when harm is threatened, 
and did not require proof of actual harm. Id. at 13. ``A statute 
allowing for regulation in the face of danger is, necessarily, a 
precautionary statute.'' Id. Optimally, the court held, regulatory 
action would not only precede, but prevent, a perceived threat. Id.
    The court also rejected petitioner's argument that any threatened 
harm must be ``probable'' before regulation was authorized. 
Specifically, the court recognized that danger ``is set not by a fixed 
probability of harm, but rather is composed of reciprocal elements of 
risk and harm, or probability and severity.'' Id. at 18. Next, the 
court held that EPA's evaluation of risk is necessarily an exercise of 
judgment, and that the statute did not require a factual finding. Id. 
at 24. Thus, ultimately, the Administrator must ``act, in part on 
`factual issues,' but largely `on choices of policy, on an assessment 
of risks, [and] on predictions dealing with matters on the frontiers of 
scientific knowledge * * * .'' Id. at 29 (citations omitted). Finally, 
the en banc court agreed with EPA that even without the language in 
section 202(a) regarding ``cause or contribute to,'' it was appropriate 
for EPA to consider the cumulative impact of lead from numerous 
sources, not just the fuels being regulated under section 211(c). Id. 
at 29-31.
b. The 1977 Clean Air Act Amendments
    The dissent in the original Ethyl Corp. decision and the en banc 
opinion were of ``critical importance'' to the House Committee which 
proposed the revisions to the endangerment language in the 1977 
amendments to the CAA. H.R. Rep. 95-294 at 48, 4 LH at 2515. In 
particular, the Committee believed the Ethyl Corp. decision posed 
several ``crucial policy questions'' regarding the protection of public 
health and welfare.'' Id. \7\ The Committee addressed those questions 
with the language that now appears in section 202(a) and several other 
CAA provisions--``emission of any air pollutant * * * , which in [the 
Administrator's] judgment cause, or contribute to, air pollution which 
may reasonably be anticipated to endanger public health or welfare.''
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    \7\ The Supreme Court recognized that the current language in 
section 202(a)(1) is ``more-protective'' than the 1970 version that 
was similar to the section 211 language before the DC Circuit in 
Ethyl Corp. Massachusetts v. EPA, 549 U.S. at 506, fn 7.
---------------------------------------------------------------------------

    The legislative history clearly indicates that the Committee 
intended the language to serve several purposes consistent with the en 
banc decision in Ethyl Corp. In particular, the language (1) emphasizes 
the preventive or precautionary nature of the CAA \8\; (2) authorizes 
the Administrator to reasonably project into the future and weigh 
risks; (3) assures the consideration of the cumulative impact of all 
sources; (4) instructs that the health of susceptible individuals, as 
well as healthy adults, should be part of the analysis; and (5) 
indicates an awareness of the uncertainties and limitations in 
information available to the Administrator. H.R. Rep. 95-294 at 49-50, 
4 LH at 2516-17.\9\
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    \8\ See H.R. Rep. 95-294 at 49, 4 LH at 2516 (``To emphasize the 
preventive or precautionary nature of the Act, i.e. to assure that 
regulatory action can effectively prevent harm before it occurs'').
    \9\ Congress also standardized this language across the various 
sections of the CAA which address emissions from both stationary and 
mobile sources. H.R. Rep. 95-294 at 50, 4 LH at 2517; Section 401 of 
CAA Amendments of 1977.
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    As noted above, the phrase ``in [her] judgment'' calls for the 
Administrator to make a comparative assessment of risks and projections 
of future possibilities, consider uncertainties, and extrapolate from 
limited data. Thus, the Administrator must balance the likelihood of 
effects with the severity of

[[Page 18892]]

the effects in reaching her judgment. The Committee emphasized that 
``judgment'' is different from a factual ``finding.'' \10\ The 
Administrator may make projections, assessments and estimates that are 
reasonable, as compared to a `` `crystal ball' inquiry.'' Moreover, 
procedural safeguards apply to the exercise of judgment, and final 
decisions are subject to judicial review. Also, the phrase ``in [her] 
judgment'' modifies both the phrases ``cause and contribute'' and ``may 
reasonably be anticipated,'' as discussed below. H.R. Rep. 95-294 at 
50-51, 4 LH at 2517-18.
---------------------------------------------------------------------------

    \10\ \\ Throughout this Notice the judgments on endangerment and 
cause or contribute are described as a finding or findings. This is 
for ease of reference only, and is not intended to imply that the 
Administrator's exercise of judgment in applying the scientific 
information to the statutory criteria is solely a factual finding; 
while grounded squarely in the science of climate change, these 
judgments also embody policy considerations.
---------------------------------------------------------------------------

    As the Committee further explained, the phrase ``may reasonably be 
anticipated'' points the Administrator in the direction of assessing 
current and future risks rather than waiting for proof of actual harm. 
This phrase is also intended to instruct the Administrator to consider 
the limitations and difficulties inherent in information on public 
health and welfare. H.R. Rep. 95-294 at 51, 4 LH at 2518.\11\
---------------------------------------------------------------------------

    \11\ Thus, contrary to the position set forth by at least one 
commenter on the Greenhouse Gas ANPR, the statutory language does 
not require that EPA prove the effects of climate change ``beyond a 
reasonable doubt.'' Indeed, such an approach is inconsistent with 
the concepts of reasonable anticipation and endangerment embedded in 
the statute.
---------------------------------------------------------------------------

    Finally, the phrase ``cause or contribute'' ensures that all 
sources of the contaminant which contribute to air pollution are 
considered in the endangerment analysis (e.g., not a single source or 
category of sources). It is also intended to require the Administrator 
to consider all sources of exposure to a pollutant (for example, food, 
water, and air) when determining risk. Id.
3. Additional Considerations for the Cause or Contribute Analysis
    By instructing the Administrator to consider whether emissions of 
an air pollutant cause or contribute to air pollution, the statute is 
clear that she need not find that emissions from any one sector or 
group of sources are the sole or even the major part of an air 
pollution problem. The use of the term contribute clearly indicates a 
lower threshold than the sole or major cause. Moreover, the statutory 
language in section 202(a) does not contain a modifier on its use of 
the term contribute. Unlike other CAA provisions, it does not require 
``significant'' contribution. See, e.g., CAA sections 111(b); 
213(a)(2), (4). Congress made it clear that the Administrator is to 
exercise her judgment in determining contribution, and authorized 
regulatory controls to address air pollution even if the air pollution 
problem results from a wide variety of sources. While the endangerment 
test looks at the entire air pollution problem and the risks it poses, 
the cause or contribute test is designed to authorize EPA to identify 
and then address what may well be many different sectors or groups of 
sources that are each part of the problem.
    The DC Circuit Court of Appeals has discussed the concept of 
contribution in the context of CAA section 213 and rules for nonroad 
vehicles. In Bluewater Network v. EPA, 370 F.3d 1 (DC Cir. 2004), 
industry argued that section 213(a)(3) requires a finding of a 
significant contribution before EPA can regulate, while EPA's view was 
that the CAA requires a finding only of contribution. Id. at 13. 
Section 213(a)(3), like section 202(a), is triggered by a finding that 
certain sources ``cause, or contribute to,'' air pollution, while an 
adjacent provision, section 213(a)(2), is triggered by a finding of a 
``significant'' contribution. The court looked at the ``ordinary 
meaning of `contribute' '' when upholding EPA's reading. After 
referencing dictionary definitions of contribute, the court also noted 
that ``[s]tanding alone, the term has no inherent connotation as to the 
magnitude or importance of the relevant `share' in the effect; 
certainly it does not incorporate any `significance' requirement.'' 370 
F.3d at 13.\12\ The court found that the bare ``contribute'' language 
invests the Administrator with discretion to exercise judgment 
regarding what constitutes a sufficient contribution for the purpose of 
making an endangerment finding. Id. at 14.\13\
---------------------------------------------------------------------------

    \12\ Specifically, the decision noted that `` `contribute' means 
simply `to have a share in any act or effect,' WEBSTER'S THIRD NEW 
INTERNATIONAL DICTIONARY 496 (1993), or `to have a part or share in 
producing,' 3 OXFORD ENGLISH DICTIONARY 849 (2d ed. 1989).'' Id. at 
13.
    \13\ The court explained, ``[t]he repeated use of the term 
`significant' to modify the contribution required for all nonroad 
vehicles, coupled with the omission of this modifier from the 
`cause, or contribute to' finding required for individual categories 
of new nonroad vehicles, indicates that Congress did not intend to 
require a finding of `significant contribution' for individual 
vehicle categories.'' Id. at 13.
---------------------------------------------------------------------------

    Like section 213(a)(3), section 202(a) refers to contribution and 
does not specify that the contribution must be significant before an 
affirmative finding can be made. To be sure, any finding of a 
``contribution'' requires some threshold to be met; a truly trivial or 
de minimis ``contribution'' might not count as such. The Administrator 
therefore has ample discretion in exercising her reasonable judgment 
and determining whether, under the circumstances presented, the cause 
or contribute criterion has been met.\14\ In the past, the 
Administrator has evaluated the emissions of the source or sources in 
different ways, based on the particular circumstances involved. For 
instance, in some mobile source rulemakings, the Administrator has used 
the percent of emissions from the regulated mobile source category 
compared to the total mobile source inventory for that air pollutant as 
the best way to evaluate contribution. See, e.g., 66 FR 5001 (2001) 
(heavy duty engine and diesel sulfur rule). In other instances the 
Administrator has looked at the percent of emissions compared to the 
total nonattainment area inventory of the air pollution at issue. See, 
e.g., 67 FR 68,242 (2002) (snowmobile rule). EPA has found that air 
pollutant emissions that amount to 1.2 percent of the total inventory 
``contribute.'' Bluewater Network, 370 F.3d at 15 (``For Fairbanks, 
this contribution was equivalent to 1.2 percent of the total daily CO 
inventory for 2001.'').
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    \14\ Section IV discusses the evidence in this case that 
supports the proposed finding of contribution. EPA need not 
determine at this time the circumstances in which emissions would be 
trivial or de minimis and would not warrant a finding of 
contribution.
---------------------------------------------------------------------------

    While these prior actions are instructive, they do not establish 
bright line emission levels above which a positive contribution 
determination must be made, or below which a contribution determination 
could not be made. The Administrator may determine that emissions at a 
certain level or percentage contribute to air pollution in one set of 
circumstances, while also judging that the same level or percentage of 
another air pollutant in a different circumstances and involving 
different air pollution does not contribute. When exercising her 
judgment, the Administrator not only considers the cumulative impact, 
but also looks at the totality of the circumstances (e.g., the air 
pollutant, the air pollution, the nature of the endangerment, the type 
of source category, the number of sources in the source category, and 
the number and type of other source categories that may emit the air 
pollutant) when determining whether the emissions ``justify 
regulation'' under the CAA. Further discussion of this issue can be 
found in Section IV.

[[Page 18893]]

4. Comments on Elements of the Endangerment and Cause or Contribute 
Tests Made During the ANPR Public Comment Period
    Certain comments submitted on the ANPR \15\ argued that when 
evaluating endangerment and cause or contribute, the Administrator is 
limited to considering only those impacts that can be traced to the 
amount of air pollution directly attributable to the greenhouse gases 
emitted by new motor vehicles and engines. Such an approach collapses 
the two prongs of the test by requiring that any climate change impacts 
upon which an endangerment determination is made result solely from the 
greenhouse gas emissions of motor vehicles. It essentially eliminates 
the ``contribute'' part of the ``cause or contribute'' portion of the 
test. This approach was clearly rejected by the en banc court in Ethyl 
Corp. 541 F.2d at 29 (rejecting the argument that the emissions of the 
fuel additive to be regulated must ``in and of itself, i.e. considered 
in isolation, endanger[s] public health.''). Moreover, it conflicts 
with an enumerated purpose of the 1977 CAA Amendments: ``To assure 
consideration of the cumulative impact of all sources of a pollutant in 
setting ambient and emission standards, not just the extent of the risk 
from the emissions from a single source or class of sources of the 
pollutant; * * *'' H.R. Rep. 95-294 at 49-50, 4 LH at 2516-17.
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    \15\ Numerous comments on the ANPR discussed the endangerment 
and cause or contribute findings, and set forth how various 
stakeholders believe EPA is compelled to make those findings. EPA 
has reviewed the comments on the ANPR, and EPA appreciates the work 
that went into them. While we are not responding to every comment 
received in today's proposal, the Agency is taking this opportunity 
to respond to a few key comments related to the test that some 
stakeholders believe guides the Administrator when undertaking an 
endangerment analysis and cause or contribute evaluation. As noted 
above, commenters should submit to the docket for today's action any 
comments they want EPA to consider as it makes a decision on this 
proposed determination.
---------------------------------------------------------------------------

    Nor does EPA agree with comments that argue the Administrator 
cannot make a positive endangerment or contribution determination 
unless the emissions reductions required by the resulting standards 
would ``effectively mitigate'' or ``fruitfully attack'' the impacts 
underlying the endangerment determination. Again, such an approach 
fails to appreciate the holistic approach that Congress adopted in 
1977. Moreover, as the Supreme Court recognized, ``[a]gencies, like 
legislatures, do not generally resolve massive problems in one fell 
regulatory swoop.'' Massachusetts v. EPA, 549 U.S. at 524 (citations 
omitted).\16\ The threshold endangerment and cause or contribute 
criteria are separate and distinct from the standard setting criteria 
that apply if the threshold findings are met, and they serve a 
different purpose. Indeed, the more serious the endangerment to public 
health and welfare, the more important it may be that action be taken 
to address the actual or potential harm even if no one action alone can 
solve the problem, and a series of actions is called for.
---------------------------------------------------------------------------

    \16\ EPA also rejects the comment that EPA has defined 
``contribute'' as resulting in a ``humanly perceptible'' difference. 
See Regional Haze Regulations and Guidelines for Best Available 
Retrofit Technology [BART] Determinations, 70 FR 39104 (2005). In 
that rule, EPA noted that a 1.0 deciview change in visibility is 
humanly perceptible in virtually all situations. Based on this, EPA 
concluded that for a state making a contribution finding for an 
individual source under section 169A(b)(2)(A), it would be 
unreasonable to determine that a source emitting pollution that 
resulted in a 0.5 deciview change in visibility did not 
``contribute'' to visibility impairment. Id. at 39120. In fact, EPA 
noted that ``[i]f `causing' visibility impairment means causing a 
humanly perceptible change in visibility, * * * then `contributing' 
to visibility impairment must mean having some lesser impact * * * 
that need not rise to the level of human perception.'' Id. at 39120, 
fn 32. The Agency did not establish a test that required human 
perception before contribution could be found.
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    Importantly, these various narrow approaches to the endangerment 
and cause or contribute criteria would effectively preclude the 
Administrator from ever making a positive finding for a global 
phenomenon like climate change because the regulatory actions would 
always be limited to just part of the picture. Indeed, they would 
preclude the Administrator from making a positive finding for any 
complex pollution problem that cannot be solved by one regulatory 
action alone. This is contrary to Congress' direction that the 
Administrator consider the whole picture when exercising her judgment 
about the critical issues of cause or contribute and endangerment to 
public health and welfare.

B. Air Pollutant, Public Health and Welfare

    The CAA defines both ``air pollutant'' and ``welfare.'' Air 
pollutant is defined as: ``Any air pollution agent or combination of 
such agents, including any physical, chemical, biological, radioactive 
(including source material, special nuclear material, and byproduct 
material) substance or matter which is emitted into or otherwise enters 
the ambient air. Such term includes any precursors to the formation of 
any air pollutant, to the extent the Administrator has identified such 
precursor or precursors for the particular purpose for which the term 
`air pollutant' is used.'' CAA section 302(g). Greenhouse gases fit 
well within this capacious definition. See Massachusetts v. EPA, 549 
U.S. at 532. They are ``without a doubt'' physical chemical substances 
emitted into the ambient air. Id. at 529. Section IV below contains 
further discussion on today's proposed definition of ``air pollutant'' 
for purposes of the contribution finding.
    Regarding ``welfare'', the CAA states that ``[a]ll language 
referring to effects on welfare includes, but is not limited to, 
effects on soils, water, crops, vegetation, man-made materials, 
animals, wildlife, weather, visibility, and climate, damage to and 
deterioration of property, and hazards to transportation, as well as 
effects on economic values and on personal comfort and well-being, 
whether caused by transformation, conversion, or combination with other 
air pollutants.'' CAA section 302(h). This definition is quite broad. 
Importantly, it is not an exclusive list due to the use of the term 
``includes, but is not limited to, * * *.'' Effects other than those 
listed here may also be considered effects on welfare.
    Moreover, the terms contained within the definition are themselves 
expansive. For example, deterioration to property could include damage 
caused by extreme weather events. Effects on vegetation can include 
impacts from changes in temperature and precipitation as well as from 
the spreading of invasive species or insects. Prior welfare effects 
evaluated by EPA include impacts on vegetation generally, and changes 
in crop and forestry specifically, as well as reduced visibility, 
changes in nutrient balance and acidity of the environment, soiling of 
buildings and statues, and erosion of building materials. See, e.g., 
Final National Ambient Air Quality Standard for Ozone, 73 FR 16436 
(2007); Control of Emissions from Nonroad Large Spark Ignition Engines 
and Recreational Engines (Marine and Land-Based), 67 FR 68242 (2002); 
Final Heavy-Duty Engine and Vehicle Standards and Highway Diesel Sulfur 
Control Requirements, 66 FR 5002 (2001).
    There is no definition of public health in the Clean Air Act. The 
Supreme Court has discussed the concept in the context of whether costs 
can be considered when setting National Ambient Air Quality Standards. 
Whitman v. American Trucking Ass'n, 531 U.S. 457 (2001). In Whitman, 
the Court imbued the term with its most natural meaning: ``the health 
of the public.'' Id. at 466.
    When considering public health, EPA has looked at morbidity, such 
as

[[Page 18894]]

impairment of lung function, aggravation of respiratory and 
cardiovascular disease, and other acute and chronic health effects, as 
well as mortality. See, e.g., Final National Ambient Air Quality 
Standard for Ozone, 73 FR 16436 (2007).

III. The Administrator's Proposed Endangerment Finding

    This section describes the basis for the proposed endangerment 
finding, by laying out the scientific evidence and the Administrator's 
rationale for reaching this judgment. The first section describes the 
approach EPA has taken in gathering and synthesizing the best available 
scientific information to inform the Administrator's judgment, the next 
section describes the proposed definition of the air pollution, and the 
third section discusses the scientific evidence and the Administrator's 
reasons for judging that the air pollution is reasonably anticipated to 
endanger both public health and public welfare.

A. Approach in Utilizing the Best Available Scientific Information

    EPA has developed a technical support document (TSD) which 
synthesizes major findings from the best available scientific 
assessments that have gone through rigorous and transparent peer 
review. The TSD therefore relies most heavily on the major assessment 
reports of both the Intergovernmental Panel on Climate Change (IPCC) 
and the U.S. Climate Change Science Program (CCSP). EPA took this 
approach rather than conducting a new assessment of the scientific 
literature. The IPCC and CCSP assessments base their findings on the 
large body of many individual, peer-reviewed studies in the literature, 
and then the IPCC and CCSP assessments themselves go through a 
transparent peer-review process. The TSD was in turn reviewed by a 
dozen federal government scientists, who have contributed significantly 
to the body of climate change literature, and indeed to our common 
understanding of this problem. The information in the TSD has therefore 
been developed and prepared in a manner that is consistent with EPA's 
Guidelines for Ensuring and Maximizing the Quality, Objectivity, 
Utility and Integrity of Information Disseminated by the Environmental 
Protection Agency.\17\ Furthermore, relying most heavily on the 
assessment reports that reflect the scientific literature more broadly 
guards against an overreliance on and narrow consideration of 
individual studies.
---------------------------------------------------------------------------

    \17\ U.S. EPA (2002), EPA/260R-02-008 http://www.epa.gov/quality/informationguidelines/documents/EPA_InfoQualityGuidelines.pdf.
---------------------------------------------------------------------------

    An earlier version of this TSD was publicly released on July 30, 
2008, to accompany the ANPR. The July 2008 version of the TSD has been 
updated to reflect the findings of 11 additional CCSP reports that have 
since been published, and to incorporate more recent climate data from 
U.S. federal agencies. This addresses a number of concerns raised by 
commenters about the July 2008 version of the TSD, arguing that it 
relied too heavily on the IPCC Fourth Assessment Report (published 
2007), which some argued was either not current enough or not specific 
enough to U.S. conditions. We note that the IPCC North American chapter 
(of the Working Group II volume) on impacts, adaptation and 
vulnerability covers the U.S. and Canada (not Mexico) and that the 
general findings in that chapter (drawn from many individual studies 
for the U.S.) are indeed applicable to U.S. conditions. Even with more 
recent information available, the IPCC Fourth Assessment Report remains 
a standard reference, essentially serving as the benchmark against 
which new findings over the next few years will be compared. Therefore 
it also serves as a robust and valuable reference for purposes of this 
proposal. The TSD has also been edited or updated in a number of places 
to reflect specific comments received on the July 2008 version, and to 
reflect comments from an additional round of review by the federal 
scientists following the incorporation of the more recent scientific 
findings.
    Regarding the scope of the relevant scientific findings, EPA took 
the approach that the timeframe under consideration should be 
consistent with the timeframe over which greenhouse gases may influence 
the climate (i.e., observed effects and projected effects over the next 
several decades and indeed at least for the remainder of this century). 
Moreover, the analysis was not restricted to only those climate and 
public health or welfare effects which may be attributable solely to 
greenhouse gas emissions from section 202(a) sources under the Act. In 
addition, although the primary focus for evaluation of risks and 
impacts to public health or welfare was on the U.S., careful 
consideration was also given to the global context.
    Finally, climate policy or societal responses to any known or 
perceived risks and impacts to public health or welfare, which may or 
may not be implemented in the future--whether through planned 
adaptation or greenhouse gas mitigation measures--were not explicitly 
assessed in the endangerment analysis. Some observed and projected 
effects or risks due to climate change reported in the TSD and 
summarized below do have embedded within them assumptions about 
autonomous behavioral or management changes to cope with climate 
change. We have noted these situations in the TSD. However, it is the 
Administrator's position that the purpose of the endangerment analysis 
is to assess the risks posed to public health and welfare, rather than 
to estimate how various adaptation and greenhouse gas mitigation 
policies may ameliorate or exacerbate any endangerment that exists. 
Indeed, the presumed need for adaptation and greenhouse gas mitigation 
to occur to avoid, lessen or delay the risks and impacts associated 
with human-induced climate change presupposes that there is 
endangerment to public health or welfare. The Administrator therefore 
disagrees with commenters on the ANPR who argue that when considering 
whether the atmospheric concentration of greenhouse gases may 
reasonably be anticipated to endanger public health or welfare, she 
must consider the impact from the regulation of greenhouse gases under 
the CAA following an endangerment finding. The Administrator also 
believes it is inappropriate, in considering whether greenhouse gases 
endanger public health or welfare, to consider potential private 
behavior aimed at alleviating some of the effects of climate change. 
Just as the Administrator would not consider, for example, the 
availability of asthma medication in determining whether criteria air 
pollutants endanger public health, so the Administrator will not 
consider private behavior in the endangerment determination at hand. On 
the contrary, ameliorative steps of that kind would attest to the fact 
of endangerment.
    To be sure, private adaptation might be considered as a relevant 
factor in deciding on the proper regulatory approach, although the 
Administrator need not decide that here. Determining whether there are 
adverse public health and welfare impacts due to the existence of air 
pollution is a separate matter from considering the appropriate 
approaches for responding to any such impacts and the possible 
repercussions of those approaches. The proposed approach suggested by 
commenters essentially would insert extra-statutory considerations into 
the endangerment analysis.

[[Page 18895]]

B. The Air Pollution

    In applying the endangerment test to greenhouse gases under section 
202(a), the Administrator must define the scope and nature of the 
relevant air pollution that must be evaluated. For this action, the 
Administrator is proposing that the air pollution be defined as the 
combined mix of six key directly-emitted and long-lived greenhouse 
gases which together constitute the root cause of human-induced climate 
change: carbon dioxide (CO2), methane, nitrous 
oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. 
The Administrator acknowledges that there are other anthropogenic 
climate forcers which play a role in climate change (discussed below), 
but that for today's action these other climate forcers are not the 
priority and may need to be evaluated further. What follows is a 
summary of key scientific findings from the TSD and the Administrator's 
rationale for the proposed definition of air pollution.
1. Common Features of the Six Key Greenhouse Gases
    There are a number of scientific and policy reasons why the 
Administrator is proposing that the air pollution for this endangerment 
finding be defined as the combination of the six greenhouse gases. 
These six greenhouse gases are well studied by and have been the 
primary focus of climate change research, and are therefore the 
Administrator's first priority in addressing endangerment for 
greenhouse gases. These six greenhouse gases share common physical 
properties relevant to the climate change problem: all are long-lived 
\18\ in the atmosphere; all become globally well mixed in the 
atmosphere regardless of where the emissions occur; all trap outgoing 
heat that would otherwise escape to space; and all are directly emitted 
as greenhouse gases rather than forming as a greenhouse gas in the 
atmosphere after emission of a precursor gas. Because of these 
properties, the climate effects of these greenhouse gases are generally 
better understood than the climate effects associated with most other 
climate-forcing agents (described in more detail in subsection 4 
below).
---------------------------------------------------------------------------

    \18\ \\ We use ``long-lived'' here to mean that the gas has a 
lifetime in the atmosphere sufficient to become globally well mixed 
throughout the entire atmosphere, which requires a minimum 
atmospheric lifetime of about one year. IPCC also refers to these 
six greenhouse gases as long-lived. Methane has an atmospheric 
lifetime of roughly a decade. One of the most commonly used 
hydrofluorocarbons (HFC-134a) has a lifetime of 14 years. Nitrous 
oxide has a lifetime of 114 years; sulfur hexafluoride over 3,000 
years; and some PFCs up to 10,000 to 50,000 years. Carbon dioxide is 
generally thought to have a lifetime of roughly 100 years, but for a 
given amount of carbon dioxide emitted some fraction is quickly 
absorbed by the oceans and terrestrial vegetation and the remainder 
will only slowly decay in the atmosphere after several years, and 
indeed some portion will remain in the atmosphere for many 
centuries.
---------------------------------------------------------------------------

    As discussed above, carbon dioxide is the most important greenhouse 
gas directly emitted by human activities in terms of its total 
additional heating effect being exerted on the climate. However, the 
other greenhouse gases are stronger heat-trapping gases compared to 
carbon dioxide on a per mass basis, \19\ and are responsible for a 
sizable fraction of the total anthropogenic climatic heating effect 
caused to date. Collectively, increased atmospheric concentrations of 
methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and 
sulfur hexafluoride have exerted an additional heating effect on the 
global climate since pre-industrial times that is about 40 percent as 
large as the additional carbon dioxide heating effect, according to the 
IPCC. Of these non-CO2 greenhouse gases, methane is the most 
important in terms of its total additional heating effect. Under all 
future scenarios, carbon dioxide is projected to remain the dominant 
driver of climate change for the remainder of this century.
---------------------------------------------------------------------------

    \19\ Global warming potentials (GWPs) for each greenhouse gas 
have been estimated by IPCC so that emissions of these gases can be 
compared to one another on a CO2-equivalent basis. The 
GWP represents the cumulative heating effect of a gas over a 
specified timeframe in the atmosphere (100 years), relative the 
heating effect caused by carbon dioxide, the reference gas. Carbon 
dioxide is assigned a GWP of 1, whereas methane has a GWP of 21. The 
GWP of sulfur hexafluoride is 23,900.
---------------------------------------------------------------------------

    Because these six greenhouse gases share common properties and are 
the key driver of human-induced climate change, they have been the 
common focus of climate change science and policy to date. The United 
Nations Framework Convention on Climate Change (UNFCCC) addresses these 
six long-lived, well-mixed greenhouse gases not controlled by the 
Montreal Protocol on Substances that Deplete the Ozone Layer. The IPCC 
scientific assessments focus primarily on these six greenhouse gases 
and their effects on climate.
    Treating the air pollution as the mix of the six greenhouse gases 
is consistent with other provisions of the Act and previous EPA 
practice under the Act, where separate air pollutants from different 
sources but with common properties may be treated as a class (e.g., 
Class I and Class II substances under Title VI). This approach 
addresses the cumulative effect that the elevated concentrations of the 
six greenhouse gases have on climate, and thus on different elements of 
health, society and the environment.\20\
---------------------------------------------------------------------------

    \20\ Due to the cumulative purpose of the statutory language, 
even if the Administrator were to look at the atmospheric 
concentration of each greenhouse gas individually, she would still 
consider the impact of the concentration of a single greenhouse gas 
in combination with that caused by the other greenhouse gases.
---------------------------------------------------------------------------

    The scientific literature that assesses the potential risks and 
end-point impacts of human-induced climate change does not typically 
assess these impacts on a gas-by-gas basis. It is true that estimates 
are available for how individual greenhouse gases and other climate-
forcing agents are contributing to the anthropogenic heating (or 
cooling) effect being exerted on the global climate. However, as one 
moves farther down the causal chain towards end-point risks and impacts 
to human health, society and the environment, such impacts, whether 
observed or projected, are typically not attributed to the temperature 
increase or other climatic change due to the elevated atmospheric 
concentration of just one of the greenhouse gases.
2. Evidence That the Six Greenhouse Gases Are at Unprecedented Levels 
in the Atmosphere
    Given the long atmospheric lifetime and global mixing of greenhouse 
gases, global average atmospheric concentrations are an important 
metric by which to measure changes in atmospheric composition. Current 
atmospheric greenhouse gas concentrations are now at elevated levels as 
a result of both historic and current anthropogenic emissions. The 
global atmospheric carbon dioxide concentration has 
increased about 38 percent from pre-industrial levels to 2009, and 
almost all of the increase is due to anthropogenic emissions. The 
current (year 2009) carbon dioxide concentration is 386 parts per 
million (ppm) and has recently been increasing by about 2.0 ppm per 
year. The global atmospheric concentration of methane has increased by 
149 percent since pre-industrial levels (through 2007), and the nitrous 
oxide concentration has increased 23 percent (through 2007). The 
observed concentration increase in these gases can also be attributed 
primarily to anthropogenic emissions. The industrial fluorinated gases, 
hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, are 
almost entirely anthropogenic in origin, and have relatively low 
atmospheric concentrations but are increasing rapidly; concentrations 
of many of these gases have increased by large factors

[[Page 18896]]

(between 4.3 and 1.3) between 1998 and 2005.
    Historic data that go back many thousands of years show that 
current atmospheric concentrations of the two most important directly 
emitted, long-lived greenhouse gases (carbon dioxide and methane) are 
well above the natural range of atmospheric concentrations compared to 
the last 650,000 years. Atmospheric greenhouse gas concentrations have 
been increasing because human emissions have been outpacing the ability 
of the natural environment to remove greenhouse gases from the 
atmosphere over timescales of decades to centuries.
    The Administrator recognizes these scientific findings that the 
current global atmospheric concentrations of the six greenhouse gases 
are now at unprecedented and record-high levels compared to both the 
recent and distant past. It is also unambiguous that the current 
elevated greenhouse gas concentrations are the primary result of human 
activities.
    Total concentrations of these greenhouse gases are projected to 
continue climbing, and thus to continue pushing unprecedented levels 
upwards for the foreseeable future under different plausible 
assumptions of U.S. and global greenhouse gas-emitting activities. 
Given the long atmospheric lifetime of the six greenhouse gases, 
significant changes in total greenhouse gas global atmospheric 
concentrations do not come about quickly (i.e., within a few years). 
Future atmospheric greenhouse gas concentrations--not only for the 
remainder of the current century but indeed for decades and in some 
cases centuries well beyond 2100--will be influenced by our present and 
near-term greenhouse gas emissions. Consideration of future plausible 
scenarios, and how our current greenhouse gas emissions essentially 
commit present and future generations to cope with an altered 
atmosphere and climate, reinforces the Administrator's judgment that it 
is appropriate to define the combination of the six key greenhouse 
gases as the air pollution.
3. Evidence That Elevated Atmospheric Concentrations of the Six 
Greenhouse Gases Are the Root Cause of Observed Climate Change
    The scientific evidence is compelling that elevated concentrations 
of heat-trapping greenhouse gases are the root cause of recently 
observed climate change. This is different from historic drivers of 
climate change, such as cyclical changes in the Earth's orbit, which 
have occurred over thousands of years.
    The global average net effect of the increase in atmospheric 
greenhouse gas concentrations, plus other human activities (e.g., land 
use change and aerosol emissions), on the global energy balance since 
1750 has been one of warming. This total net heating effect, referred 
to as forcing, is estimated to be 1.6 Watts per square meter (W/m\2\), 
with much of the range surrounding this estimate due to uncertainties 
about the cooling and warming effects of aerosols. The combined 
radiative forcing due to the cumulative increase in atmospheric 
concentrations of carbon dioxide, methane, and nitrous oxide over the 
period 1750 to 2005 is 2.30 W/m\2\. The positive radiative forcing due 
to carbon dioxide is the largest (1.66 W/m\2\). Methane is the second 
largest source of positive radiative forcing (0.48 W/m\2\). Nitrous 
oxide has a positive radiative forcing of 0.16 W/m\2\. The rate of 
increase in forcing due to these three greenhouse gases during the 
industrial era is, according to IPCC, very likely \21\ to have been 
unprecedented in more than 10,000 years.
---------------------------------------------------------------------------

    \21\ According to IPCC terminology, ``very likely'' conveys a 90 
to 99 percent probability of occurrence. ``Virtually certain'' 
conveys a greater than 99 percent probability, and ``likely'' 
conveys a 66 to 90 percent probability.
---------------------------------------------------------------------------

    Warming of the climate system is now unequivocal, as is evident 
from observations of increases in global average air and ocean 
temperatures, widespread melting of snow and ice, and rising global 
average sea level. Global mean surface temperatures have risen by 0.74 
[deg]C (1.3 [deg]F) over the last 100 years. Eight of the ten warmest 
years on record have occurred since 2001. Global mean surface 
temperature was higher during the last few decades of the 20th century 
than during any comparable period during the preceding four centuries.
    Most of the observed increase in global average temperatures since 
the mid-20th century is very likely due to the observed increase in 
anthropogenic greenhouse gas concentrations. Global observed 
temperatures over the last century can be reproduced only when model 
simulations include both natural and anthropogenic forcings, that is, 
simulations that remove anthropogenic forcings are unable to reproduce 
observed temperature changes. Thus, most of the warming cannot be 
explained by natural variability, such as variations in solar activity.
    In addition to attributing recent global warming to anthropogenic 
greenhouse gas influence at the global scale, both the IPCC and CCSP 
reports attributed recent North American warming to elevated greenhouse 
gas concentrations. A 2008 CCSP report \22\ found that for North 
America, ``more than half of this warming [for the period 1951-2006] is 
likely \23\ the result of human-caused greenhouse gas forcing of 
climate change.''
---------------------------------------------------------------------------

    \22\ \\ CCSP (2008) Reanalysis of Historical Climate Data for 
Key Atmospheric Features: Implications for Attribution of Causes of 
Observed Change. A Report by the U.S. Climate Change Science Program 
and the Subcommittee on Global Change Research [Randall Dole, Martin 
Hoerling, and Siegfried Schubert (eds.)]. National Oceanic and 
Atmospheric Administration, National Climatic Data Center, 
Asheville, NC, 156 pp.
    \23\ This CCSP report used likelihood terminology that is 
consistent with that used by IPCC where ``likely'' also conveys a 66 
to 90 percent probability of occurrence.
---------------------------------------------------------------------------

    Therefore, by defining air pollution as the six greenhouse gases, 
the Administrator is identifying the fundamental and underlying driver 
of human-induced climate change, which in turn, as described below, 
poses risks to human health, society, and the environment. The 
Administrator believes that the proposed definition of air pollution 
captures the root of the problem, and addresses the part of the problem 
that is best understood, scientifically speaking, and that is already 
the focus of scientists and policy analysts involved in studying 
climate change. Because the six greenhouse gases are collectively the 
primary driver of the climate change problem, all current and future 
risks due to human-induced climate change--whether these risks are 
associated with increases in temperature, changes in precipitation, a 
rise in sea levels, changes in the frequency and intensity of weather 
events, or more directly with the elevated greenhouse gas 
concentrations themselves--can be associated with this definition of 
``air pollution.'' This does not imply that other anthropogenic climate 
forcers, discussed below, would pose no risks. EPA has considered 
whether other climate-forcing agents in addition to the six greenhouse 
gases should be included in this proposed definition of air pollution, 
and for the reasons discussed below is not proposing to include them in 
the definition of air pollution for purposes of this proposed 
endangerment finding.
4. Other Climate Forcers
    There are other greenhouse gases and aerosols that have warming 
(and cooling) effects but are not being included in the proposed 
definition of air pollution. These include water vapor, 
chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs),

[[Page 18897]]

halons, tropospheric ozone (O3), black carbon, and other 
short-lived precursor gases. For each of these substances, there are 
different scientific and policy reasons why these substances are not 
being included in the proposed definition of air pollution for purposes 
of section 202(a).
a. Water Vapor
    Water vapor is the most abundant naturally occurring greenhouse gas 
and therefore makes up a significant share of the natural, background 
greenhouse effect. However, direct water vapor emissions from human 
activities have only a negligible effect on atmospheric concentrations 
of water vapor, whereas direct emissions of the six greenhouse gases 
have significantly altered the global atmospheric concentrations of 
those gases, as detailed above. Significant changes to global 
atmospheric concentrations of water vapor can occur indirectly through 
human-induced global warming, which then increases the amount of water 
vapor in the atmosphere because a warmer atmosphere can hold more 
moisture. Therefore, changes in water vapor concentrations are not an 
initial driver of climate change, but rather an effect of climate 
change which then acts as a positive feedback that further enhances 
warming. For this reason, the IPCC does not list direct emissions of 
water vapor as an anthropogenic forcing agent of climate change, but 
does include this water vapor feedback mechanism in response to human-
induced warming in all modeling scenarios of future climate change. 
Based on this recognition that anthropogenic emissions of water vapor 
are a negligible driver of anthropogenic climate change, EPA's annual 
Inventory of U.S. Greenhouse Gas Emissions and Sinks does not include 
water vapor, and greenhouse gas inventory reporting guidelines under 
the UNFCCC do not require data on water vapor emissions.
    Water vapor may be an issue of concern when it is emitted by 
aircraft at high altitudes, where, under certain conditions, it can 
lead to the formation of condensation trails, referred to as contrails. 
Similar to high-altitude, thin clouds, contrails have a warming effect. 
Extensive cirrus clouds can also develop from aviation contrails, and 
increases in cirrus cloud cover would also have a warming effect. The 
IPCC Fourth Assessment Report estimated a very small positive heating 
effect for linear contrails, with a low degree of scientific 
understanding. Unlike the warming effects associated with the six long-
lived, well-mixed greenhouse gases, the warming effects associated with 
contrails or contrail-induced cirrus cloud cover are more regional and 
temporal in nature. EPA has received a petition under the Act to 
consider the regulation of aircraft emissions (water vapor and NOx) 
that lead to formation of contrails (in addition to aircraft greenhouse 
gas emissions), and EPA plans to evaluate this issue further. At this 
time, the Administrator is not proposing to include aircraft-related 
contrails or emissions that are not greenhouse gases within the 
definition of air pollution for purposes of section 202(a).
b. The Ozone-Depleting Substances: CFCs, HCFCs and Halons
    Chlorofluorocarbons (CFCs), hydro-chlorofluorocarbons (HCFCs) and 
halons are ozone-depleting substances that have been responsible for 
the depletion of stratospheric ozone, which prevents harmful forms of 
ultraviolet radiation from reaching the Earth's surface. The Montreal 
Protocol on Substances that Deplete the Ozone Layer is an international 
agreement that controls these substances. In the U.S., these substances 
are being controlled and phased out under Title VI of the Act. Despite 
their ozone-depleting properties, which the six greenhouse gases in the 
definition of air pollution do not share, these substances share other 
common physical properties with the six greenhouse gases: They are also 
long-lived in the atmosphere; well mixed throughout the global 
atmosphere; are directly emitted by anthropogenic sources; and have 
been responsible for a share of the human-induced heating effect to 
date. However, these substances have not been a priority for the 
scientists and policy analysts involved in studying climate change, and 
they are not a priority for the Administrator for this action. The 
UNFCCC does not address these substances and instead defers their 
treatment to the Montreal Protocol. The Administrator is not proposing 
to include these substances in the definition of air pollution with 
this action, but will continue to consider these issues.
c. Tropospheric Ozone
    Increased concentrations of tropospheric O3 are 
estimated to be causing a significant anthropogenic warming effect. 
However, unlike the long-lived six greenhouse gases, tropospheric 
O3 has a short atmospheric lifetime (hours to weeks) and 
therefore its concentrations are more variable over space and time. For 
these reasons, its global heating effect and contribution to climate 
change tend to entail greater uncertainty compared to the well-mixed, 
long-lived greenhouse gases. Tropospheric O3 is also not a 
directly emitted greenhouse gas, but rather undergoes secondary 
formation in the atmosphere from the emission of precursor gases such 
as nitrogen oxides (NOX) and volatile organic compounds 
(VOCs). For these reasons, the Administrator is not including 
tropospheric O3 in the proposed definition of air pollution 
with this action.
d. Black Carbon
    Black carbon is not a greenhouse gas but an aerosol particle that 
results from incomplete combustion of the carbon contained in fossil 
fuels, and remains in the atmosphere for only about a week. Black 
carbon is a component of particulate matter (PM), which is regulated as 
a criteria air pollutant under the Act. Scientific studies have found 
an association between exposure to PM and significant health problems.
    Black carbon causes a warming effect by absorbing incoming sunlight 
(whereas greenhouse gases cause warming by trapping outgoing, infrared 
heat), and by darkening bright surfaces such as snow and ice, which 
reduces reflectivity. This latter effect in particular has been raising 
concerns about the role black carbon may be playing in observed warming 
and ice melt in the Arctic.
    Black carbon is co-emitted with other pollutants, especially 
organic carbon, which all tend to have a direct cooling effect on 
climate because they reflect and scatter incoming sunlight. However, 
black carbon, per unit mass, is a more effective warming agent than 
organic carbon is a cooling agent. The IPCC Fourth Assessment Report 
estimated that co-emissions of organic carbon may be offsetting about 
40 percent of black carbon's warming effect on a global average. The 
ratio of black carbon to organic carbon varies by fuel type and by 
combustion efficiency, such that different emission sources will have 
different net climate effects; likewise, different emission reduction 
measures will have different net climate effects. Furthermore, because 
black carbon is short lived in the atmosphere, the net climate effect 
of a black carbon emission source will also depend on location; for 
example, emissions that deposit on snow and ice, or get lofted above 
cloud surfaces, could have a stronger warming effect. Like other 
aerosols, black carbon can also affect the reflectivity and lifetime of 
clouds. How black carbon and other aerosols, such as sulfates, alter 
cloud properties is a key source of uncertainty in quantifying the 
total

[[Page 18898]]

human influence on the global climate. This total cloud indirect effect 
caused by all aerosols (e.g., sulfates, black carbon and organic 
carbon) is estimated to be causing a net cooling effect, with a large 
range of uncertainty. Given these reasons, there is considerably more 
uncertainty associated with black carbon's warming effect compared to 
the estimated warming effect of the six long-lived greenhouse gases.
    Given the number of science issues for black carbon that are 
different than for the six greenhouse gases, the Administrator is not 
proposing to include black carbon in the definition of air pollution 
for purposes of section 202(a) with this action. However, EPA is 
already undertaking work to further evaluate the role of black carbon 
in climate change, in addition to its role as an element of the 
already-regulated PM2.5. Indeed, a recent study \24\ 
referenced in the TSD estimated that black carbon is having a much 
stronger direct warming effect (160 percent higher on a global average) 
compared to IPCC's estimate. EPA has also received petitions to 
specifically address black carbon emissions under the Act from marine 
and aviation sources, and EPA plans to respond to these petitions in a 
separate action.
---------------------------------------------------------------------------

    \24\ \\ Ramanathan V. and G. Carmichael (2008) Global and 
regional climate changes due to black carbon. Nature Geoscience, 1: 
221-227.
---------------------------------------------------------------------------

e. Fluorinated Ethers and Recently Identified Greenhouse Gases
    Fluorinated ethers are used in electronics, anesthetics, and as 
heat transfer fluids. Like the six greenhouse gases included in the 
proposed definition of air pollution, these fluorinated compounds have 
heat-trapping properties and can also be long-lived in the atmosphere. 
In many cases these fluorinated gases are used in expanding industries 
(e.g., electronics) or as substitutes for hydrofluorocarbons. Also, new 
compounds that have greenhouse gas attributes continue to be 
discovered, such as nitrogen trifluoride (NF3). The IPCC has 
now assigned global warming potentials (GWPs) to both fluorinated 
ethers and NF3. However, the total global radiative forcing 
contribution of these compounds is not yet available to compare with 
the anthropogenic heating effect caused by the six greenhouse gases. 
The Administrator is not proposing to include these gases in the 
definition of air pollution with this action.

C. The Administrator's Proposed Finding That the Air Pollution 
Endangers Public Health and Welfare

    The scientific evidence clearly indicates that atmospheric levels 
of the six greenhouse gases are at unprecedented elevated levels due to 
human activities, and that most of the observed global and continental 
warming can be attributed to this anthropogenic rise in greenhouse 
gases. The information presented here builds on these facts that 
support the proposed definition of air pollution.
    Based on the total weight of evidence, which is briefly summarized 
here and set forth in more detail in the TSD, it is the Administrator's 
judgment that current and projected levels of the mix of the six 
greenhouse gases endanger the public health and welfare of current and 
future generations.
    The Administrator's proposed endangerment finding is based on the 
entire range of observed risks and potential harms to public health and 
welfare. The Administrator is not basing her proposal on any one 
impact, but instead is weighing the evidence collectively and 
determining that as a whole it clearly indicates that the air pollution 
at issue endangers public health and welfare now and in the future.
    Furthermore, the Administrator is taking into account a number of 
key considerations that provide guidance on how to weigh and interpret 
the collective body of scientific evidence for today's proposal, 
namely: The observed record of climate change and our ability to 
attribute these changes to the observed anthropogenic buildup of 
greenhouse gases in the atmosphere; plausible future changes in climate 
over the next several decades and beyond given both the accumulation of 
greenhouse gases in the atmosphere to date plus expected increases in 
concentrations under different scenarios of future greenhouse gas 
emission pathways; the level of certainty with which we can reasonably 
project both near- and long-term climate change; our ability to 
identify known risks to public health and welfare, both today and in 
the future in light of a continually changing climate; the 
vulnerability of particularly susceptible populations and regions; the 
likelihood that such risks to both public health and welfare are 
happening now and will happen in the future; the magnitude of such 
risks and impacts to public health and welfare; and finally a 
consideration of how key gaps in our knowledge of current, but 
especially future, effects factor into an endangerment decision.
    The following discussion sets forth the Administrator's rationale 
for making this proposed endangerment finding, including a description 
of the supporting scientific findings showing evidence of the effects 
that elevated greenhouse gas concentrations are having currently and 
are projected to have in the future, and the implications of these 
effects for public health and welfare.
1. Evidence of Currently Observed Climatic and Related Effects
    There is compelling evidence that a number of climate and physical 
changes are occurring now that can be attributed to the anthropogenic 
rise in atmospheric greenhouse gases, and other changes that are 
consistent with the direction of change expected from warming and 
human-induced climate change. These observed changes described below 
can adversely affect and pose risks to both public health and welfare.
    The global indicators of change go beyond the well-established 
surface air temperature rise discussed above. Observational evidence 
from all continents and most oceans shows that many natural systems are 
being affected by regional climate changes, particularly temperature 
increases. Observations show that changes are occurring in the amount, 
intensity, frequency, and type of precipitation. There is strong 
evidence that global sea level gradually rose in the 20th century and 
is currently rising at an increased rate. Widespread changes in extreme 
temperatures have been observed in the last 50 years. Globally, cold 
days, cold nights, and frost have become less frequent, while hot days, 
hot nights, and heat waves have become more frequent.
    Satellite data since 1978 show that annual average Arctic sea ice 
extent has shrunk by 2.7  0.6 percent per decade, with 
larger decreases in summer of 7.4  2.4 percent per decade. 
The latest data from NASA indicate Arctic sea ice set a record low in 
September 2007, 38 percent below the 1979-2007 average. In September 
2008, Arctic sea ice reached its second lowest extent on record.
    Like global mean temperatures, U.S. air temperatures have warmed 
during the 20th and into the 21st century. According to official data 
from NOAA's National Climatic Data Center:
     U.S. average annual temperatures are now approximately 
1.25 [deg]F (0.69 [deg]C) warmer than at the start of the 20th century, 
with an increased rate of warming over the past 30 years. The rate of 
warming for the entire period of record (1895-2008) is 0.13 [deg]F/
decade while the rate of warming increased to

[[Page 18899]]

0.58 [deg]F/decade (0.32 [deg]C/decade) for the period from 1979-2008.
     2005-2007 were exceptionally warm years (among the top 10 
warmest on record), while 2008 was slightly warmer than average (the 
39th warmest year on record), 0.2 [deg]F (0.1 [deg]C) above the 20th 
century (1901-2000) mean.
     The last ten 5-year periods (2004-2008, 2003-2007, 2002-
2006, 2001-2005, 2000-2004, 1999-2003, 1998-2002, 1997-2001, 1996-2000, 
and 1995-1999), were the warmest 5-year periods in the 114 years of 
national records, demonstrating the anomalous warmth of the last 15 
years.
    Over the contiguous U.S., total annual precipitation increased at 
an average rate of 6.5 percent over the period 1901-2006. It is likely 
that there have been increases in the number of heavy precipitation 
events within many land regions, even in those where there has been a 
reduction in total precipitation amount, consistent with a warming 
climate.
    Sea level has been rising along most of the U.S. Atlantic and Gulf 
coasts. In the mid-Atlantic region from New York to North Carolina, 
tide-gauge observations indicate that relative sea-level rise (the 
combination of global sea-level rise and land subsidence) rates were 
higher than the global mean and generally ranged between 2.4 and 4.4 
millimeters per year, or about 0.3 meters (1 foot) over the twentieth 
century.
    Climate changes are very likely already affecting U.S. water 
resources, agriculture, land resources, and biodiversity as a result of 
climate variability and change. A 2008 CCSP report \25\ that examined 
these observed changes concluded, ``[t]he number and frequency of 
forest fires and insect outbreaks are increasing in the interior West, 
the Southwest, and Alaska. Precipitation, stream flow, and stream 
temperatures are increasing in most of the continental U.S. The western 
U.S. is experiencing reduced snowpack and earlier peaks in spring 
runoff. The growth of many crops and weeds is being stimulated. 
Migration of plant and animal species is changing the composition and 
structure of arid, polar, aquatic, coastal, and other ecosystems.''
---------------------------------------------------------------------------

    \25\ Backlund, P., A. Janetos, D.S. Schimel, J. Hatfield, M.G. 
Ryan, S.R. Archer, and D. Lettenmaier (2008) Executive Summary. In: 
The effects of climate change on agriculture, land resources, water 
resources, and biodiversity in the United States. A Report by the 
U.S. Climate Change Science Program and the Subcommittee on Global 
Change Research. Washington, DC., USA, 362 pp.
---------------------------------------------------------------------------

    Regarding observed changes in extreme events, another 2008 CCSP 
report \26\ stated the following: ``Many extremes and their associated 
impacts are now changing. For example, in recent decades most of North 
America has been experiencing more unusually hot days and nights, fewer 
unusually cold days and nights, and fewer frost days. Heavy downpours 
have become more frequent and intense. Droughts are becoming more 
severe in some regions, though there are no clear trends for North 
America as a whole. The power and frequency of Atlantic hurricanes have 
increased substantially in recent decades, though North American 
mainland land-falling hurricanes do not appear to have increased over 
the past century. Outside the tropics, storm tracks are shifting 
northward and the strongest storms are becoming even stronger.''
---------------------------------------------------------------------------

    \26\ Karl, T.R., G.A. Meehl, T.C. Peterson, K.E. Kunkel, W.J. 
Gutowski, Jr., D.R. Easterling (2008) Executive Summary in Weather 
and Climate Extremes in a Changing Climate. Regions of Focus: North 
America, Hawaii, Caribbean, and U.S. Pacific Islands. T.R. Karl, 
G.A. Meehl, C.D. Miller, S.J. Hassol, A.M. Waple, and W.L. Murray 
(eds.). A Report by the U.S. Climate Change Science Program and the 
Subcommittee on Global Change Research, Washington, DC.
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2. Future Projected Climatic and Related Effects
    Because atmospheric greenhouse gas concentrations are expected to 
climb for the foreseeable future, temperatures will continue to rise 
and the overall rate and magnitude of human-induced climate change will 
likely increase, such that risks to public health and welfare will 
likewise grow over time so that future generations will be especially 
vulnerable; their vulnerability will include potentially catastrophic 
harms. Projected effects here focus on the next several decades and the 
timeframe out to 2100.
    The majority of future reference-case scenarios (assuming no 
explicit greenhouse gas mitigation actions beyond those already 
enacted) project an increase of global greenhouse gas emissions over 
the century, with climbing greenhouse gas concentrations. Long-lived 
gas concentrations increase even for those scenarios where annual 
emissions toward the end of the century are assumed to be lower than 
current annual emissions. Indeed, for a given amount of CO2 
released today, about half will be taken up by the oceans and 
terrestrial vegetation over the next 30 years, a further 30 percent 
will be removed over a few centuries, and the remaining 20 percent will 
only slowly decay over time such that it will take many thousands of 
years to remove from the atmosphere. Carbon dioxide is expected to 
remain the dominant anthropogenic driver of climate change over the 
course of the 21st century. The heating effect associated with the non-
CO2 greenhouse gases is still significant and growing over 
time.
    Future warming over the course of the 21st century, even under 
scenarios of low emissions growth, is very likely to be greater than 
observed warming over the past century (Figure 1). Through about 2030, 
the global warming rate is affected little by the choice of different 
future emission scenarios, according to IPCC. By mid-century, the 
choice of scenario becomes more important for the magnitude of the 
projected warming; About a third of that warming is projected to be due 
to climate change that is already committed. By the end of the century, 
projected average global warming (compared to average temperature 
around 1990) varies significantly depending on emissions scenario and 
climate sensitivity assumptions, ranging from 1.8 to 4.0 [deg]C (3.2 to 
7.2 [deg]F), with an uncertainty range of 1.1 to 6.4 [deg]C (2.0 to 
11.5 [deg]F), according to the IPCC.

[[Page 18900]]

[GRAPHIC] [TIFF OMITTED] TP24AP09.052

    Global mean precipitation is expected to increase with global 
warming. However, there are substantial spatial and seasonal 
variations. Increases in the amount of precipitation are very likely in 
high latitudes, while decreases are likely in the mid-latitudes and 
semi-arid low latitudes including much of the already water-stressed 
southwestern U.S., continuing observed patterns in recent trends. 
Drought is expected to increase in the western U.S., where water 
availability to meet demands for agricultural and municipal water needs 
is already limited. Another projected impact in the western U.S. is 
decreased water availability due to a range of inter-connected factors. 
These include: decreased snowpack, earlier snowmelt resulting in peak 
winter and decreased summer flows, which will disrupt and limit water 
storage capacity and will create additional challenges for water 
allocation among competing uses (agricultural, municipal, industrial, 
ecological). Rising sea levels could lead to salt water intrusion of 
coastal ground aquifers, which would further reduce freshwater 
availability for municipal and agricultural use among coastal 
communities that depend on these aquifers.
    By the end of the century, sea level is projected by IPCC to rise 
between 0.18 and 0.59 meters relative to around 1990 in the absence of 
increased dynamic ice sheet loss. Recent rapid changes at the edges of 
the Greenland and West Antarctic ice sheets show acceleration of flow 
and thinning. While understanding of these ice sheet processes is 
incomplete, their inclusion in models would likely lead to increased 
sea-level projections for the end of the 21st century. Sea ice is 
projected to shrink in the Arctic under all IPCC emission scenarios.
    All of the U.S. is very likely to warm during this century, and 
most areas of the U.S. are expected to warm by more than the global 
average. The largest warming through 2100 is projected to occur in 
winter over northern parts of Alaska. In western, central and eastern 
regions of North America, the projected warming has less seasonal 
variation and is not as large, especially near the coast, consistent 
with less warming over the oceans.
    The U.S is projected to see an overall average increase in the 
intensity of precipitation events, which is likely to increase the risk 
of flood events, though projections for specific regions are very 
uncertain.
    As the climate warms, glaciers will lose mass owing to dominance of 
summer melting over winter precipitation increases, contributing to sea 
level rise.
    For North American coasts, sea level rise may be similar to the 
global mean, with slightly higher rates in western Alaska. The 
projected rate of sea level

[[Page 18901]]

rise off the low-lying U.S. South Atlantic and Gulf coasts is also 
higher than the global average.
    Based on a range of models, it is likely that tropical cyclones 
(tropical storms and hurricanes) will become more intense, with 
stronger peak winds and more heavy precipitation associated with 
ongoing increases of tropical sea surface temperatures. Storm surge 
levels are likely to increase due to projected sea level rise. 
Frequency changes in hurricanes are currently too uncertain for 
confident projections.
3. Impacts on Public Health
    Many of the observed and projected changes in climate and climate-
sensitive systems discussed above pose serious risks to public health. 
The following discussion outlines specific public health concerns 
raised by observations and plausible future outcomes, recognizing the 
statutory requirement that the Administrator consider how sensitive or 
susceptible populations may be particularly at risk. As our discussion 
of increasing temperatures suggests, the adverse effects of greenhouse 
gas emissions are expected to mount over time. The findings of the 
IPCC, and of many others, indicate that risks to public health will be 
more severe in 20 years than in ten years, more severe in 30 years than 
in 20 years, more severe in 40 years than in 30 years, and so forth. 
There is disagreement about whether and when increases in adverse 
effects will be linear or nonlinear; on some projections, nonlinear 
increases in such effects can reasonably be expected at some future 
point. We believe that existing evidence supports a finding that there 
are current adverse effects. This evidence also supports a finding that 
these effects will become more serious over the next several decades, 
in some cases out to 2100.
    To be clear, ambient concentrations of carbon dioxide and the other 
greenhouse gases, whether at current levels or at projected ambient 
levels under scenarios of high emissions growth over time, do not cause 
direct adverse health effects such as respiratory or toxic effects. All 
public health risks and impacts described here as a result of elevated 
atmospheric concentrations of greenhouse gases occur via climate 
change. The pathway or mechanism occurs through changes in climate, but 
the end result is an adverse effect on the health of the population. 
Thus these effects from climate change are appropriately denoted public 
health effects. It is important to acknowledge that effects on 
``welfare'' do not always entail effects on ``public health,'' and the 
Administrator does not mean to interpret ``public health'' to include 
``welfare'' effects as such. Today's interpretation does not collapse 
the two categories--many ``welfare'' effects do not and cannot involve 
public health. The Administrator simply means to recognize, with the 
scientific community, that concentrations of greenhouse gases endanger 
public health through a wide range of pathways.
    As described above, there is evidence that unusually hot days and 
nights and heat waves have become more frequent in the U.S. Severe heat 
waves are projected to intensify in magnitude and duration over the 
portions of the U.S. where these events already occur, with likely 
increases in mortality and morbidity. The populations most sensitive to 
hot temperatures are older adults, the chronically sick, the very 
young, city-dwellers, those taking medications that disrupt 
thermoregulation, the mentally ill, those lacking access to air 
conditioning, those working or playing outdoors, and the socially 
isolated.
    The Administrator also acknowledges that warming temperatures may 
bring about some health benefits. Both extremely cold days and 
extremely hot days are dangerous to human health. But at least in the 
short run, modest temperature increases may produce health benefits in 
the U.S. (and elsewhere). Although the IPCC projects reduced human 
mortality from cold exposure through 2100, it is currently difficult to 
ascertain the balance between increased heat-related mortality and 
decreased cold-related mortality. With respect to health, different 
regions will be affected in different ways. The Administrator does not 
believe that it is now possible to quantify the various effects. 
Because the risks from unusually hot days and nights, and from heat 
waves, are very serious, it is reasonable to find on balance that these 
risks support a finding that public health is endangered even if it is 
also possible that modest temperature increases will have some 
beneficial health effects.
    Increases in regional ozone pollution in the U.S. relative to ozone 
levels without climate change are expected due to higher temperatures 
and a modification of meteorological factors. Increases in regional 
ozone pollution increase the risks of respiratory infection, 
aggravation of asthma, and premature death. EPA does have in place 
National Ambient Air Quality Standards (NAAQS) for ozone, which are 
premised on the harmfulness of ozone to public health and welfare. 
These standards and their accompanying regulatory regime have helped to 
reduce the dangers from ozone in the U.S. Substantial challenges remain 
with respect to achieving the air quality protection promised by the 
NAAQS for ozone. These challenges will be exacerbated by climate 
change.
    There will likely be an increase in the spread of several food and 
water-borne pathogens (e.g., Salmonella, Vibrio) among susceptible 
populations depending on the pathogens' survival, persistence, habitat 
range and transmission under changing climate and environmental 
conditions. The primary climate-related factors that affect these 
pathogens include temperature, precipitation, extreme weather events, 
and shifts in their ecological regimes.
    Climate change, including the direct changes in carbon dioxide 
concentrations themselves, could impact the production, distribution, 
dispersion and allergenicity of aeroallergens and the growth and 
distribution of weeds, grasses and trees that produce them. These 
changes in aeroallergens and subsequent human exposures could affect 
the prevalence and severity of allergy symptoms. However, the 
scientific literature does not provide definitive data or conclusions 
on how climate change might impact aeroallergens and subsequently the 
prevalence of allergenic illnesses in the U.S.
    The IPCC reports with very high confidence \27\ that climate change 
impacts on human health in U.S. cities will be compounded by population 
growth and an aging population. The CCSP reports that climate change 
has the potential to accentuate the disparities already evident in the 
American health care systems as many of the expected health effects are 
likely to fall disproportionately on the poor, the elderly, the 
disabled, and the uninsured.
---------------------------------------------------------------------------

    \27\ According to the IPCC lexicon, ``very high confidence'' 
conveys at least a 9 out of 10 chance of being correct. ``High 
confidence'' conveys an 8 out of 10 chance of being correct, and 
``medium confidence'' a 5 out of 10 chance.
---------------------------------------------------------------------------

    Within settlements experiencing climate change stressors, certain 
parts of the population may be especially vulnerable based on their 
circumstances. These include the poor, the elderly, the very young, 
those already in poor health, the disabled, those living alone, those 
with limited rights and power (such as recent immigrants with limited 
English skills), and/or indigenous populations dependent on one or a 
few resources.

[[Page 18902]]

    These potential impacts of climate change have taken on added 
meaning in light of the risk that hurricanes are likely to become more 
severe with climate change, and in light of our heightened awareness 
about how vulnerable the U.S. Gulf Coast can be.
    Some have argued that a positive endangerment finding for public 
health cannot be made because the health effects associated with 
elevated atmospheric concentrations of greenhouse gases occur via 
climate change, and not directly through inhalation or other exposure 
to the greenhouse gases themselves. These commenters argue that because 
``climate'' is included in the definition of welfare, the Act requires 
that all effects which may flow from a welfare effect must themselves 
be considered a welfare effect. The Administrator disagrees with this 
narrow view of the endangerment criteria. Mortality and morbidity that 
result from the effects of climate change are clearly public health 
problems. It would be anomalous to argue that a person who is injured 
or dies from heat exhaustion or increased exposure to a pathogen has 
not suffered a health impact. In addition, tropospheric ozone is 
already regulated under the Act as a criteria air pollutant in part due 
to its adverse impacts on public health. It is estimated that climate 
change can exacerbate tropospheric ozone levels in some parts of the 
U.S. The Administrator rejects a position that would treat the adverse 
effects on the health of individuals caused by tropospheric ozone as 
something other than a public health threat because they are 
exacerbated by climate change.
4. Impacts on Public Welfare
    The Act defines ``effects on welfare'' as including, but not 
limited to, ``effects on soils, water, crops, vegetation, manmade 
materials, animals, wildlife, weather, visibility, and climate, damage 
to and deterioration of property, and hazards to transportation, as 
well as effects on economic values and on personal comfort and well-
being * * *'' CAA Section 302(h). It is clear that current and 
projected levels of greenhouse gases and resultant climate change are 
already adversely affecting, and will continue to adversely affect, 
public welfare within the meaning of the Act. As noted, the adverse 
effects of greenhouse gases are expected to increase over time with 
growing temperatures. This point holds for welfare as it does for 
health. In the future, the adverse effects will increase and perhaps 
accelerate; projected risks focus on the next several decades and out 
to 2100.
    As heavy rainfall events are expected to become more intense, there 
is an increased risk of flooding, greater runoff and erosion, and thus 
the potential for adverse water quality effects.
    Climate change will likely further constrain already over-allocated 
water resources in some sections of the U.S., increasing competition 
among agricultural, municipal, industrial, and ecological uses. 
Although current water management practices in the U.S. are generally 
advanced, particularly in the West, climate change increasingly creates 
conditions well outside of historical observations. Rising temperatures 
will diminish snowpack and increase evaporation, affecting seasonal 
availability of water. In the Great Lakes and major river systems, 
lower levels are likely to exacerbate challenges relating to water 
quality, navigation, recreation, hydropower generation, water 
transfers, and bi-national relationships. Higher water temperatures, 
increased precipitation intensity, and longer periods of low flows can 
exacerbate many forms of water pollution. Decreased water supply and 
lower water levels are likely to exacerbate challenges relating to 
navigation in the U.S.
    CCSP concluded that, with increased CO2 and temperature, 
the life cycle of grain and oilseed crops will likely progress more 
rapidly. But, as temperature rises, these crops will increasingly begin 
to experience failure, especially if climate variability increases and 
precipitation lessens or becomes more variable. Furthermore, the 
marketable yield of many horticultural crops--e.g., tomatoes, onions, 
fruits--is very likely to be more sensitive to climate change than 
grain and oilseed crops. The IPCC reported that moderate climate change 
in the early decades of the century is projected to increase aggregate 
yields of rain-fed agriculture in North America as a whole by 5-20 
percent, but with important variability among regions. However, like 
CCSP, IPCC further stated that major challenges are projected for crops 
that are near the warm end of their suitable range or depend on highly 
utilized water resources.
    Higher temperatures will very likely reduce livestock production 
during the summer season, but these losses will very likely be 
partially offset by warmer temperatures during the winter season.
    Climate change has very likely increased the size and number of 
forest fires, insect outbreaks, and tree mortality in the interior 
west, the Southwest, and Alaska, and will continue to do so. An 
increased frequency of disturbance is at least as important to 
ecosystem function as incremental changes in temperature, 
precipitation, atmospheric CO2, nitrogen deposition, and 
ozone pollution. IPCC reported that overall forest growth for North 
America as a whole will likely increase modestly (10-20 percent) as a 
result of extended growing seasons and elevated CO2 over the 
next century, but with important spatial and temporal variation.
    In addition to human health effects, tropospheric ozone increases 
as a result of temperature increases and other climatic changes can 
have significant adverse effects on crop yields, pasture and forest 
growth and species composition.
    Coastal communities and habitats will be increasingly stressed by 
climate change impacts interacting with development and pollution. Sea 
level is rising along much of the U.S. coast, and the rate of change 
will increase in the future, exacerbating the impacts of progressive 
inundation, storm-surge flooding, and shoreline erosion. Coastal 
aquifers and estuaries are vulnerable to salt water intrusion due to 
rising sea levels, which could compromise water sources used for 
municipal drinking water, agricultural crops, and other human uses. 
Storm impacts are likely to be more severe, especially along the Gulf 
and Atlantic coasts. Salt marshes, other coastal habitats, and 
dependent species are threatened by sea-level rise, fixed structures 
blocking landward migration, and changes in vegetation. Population 
growth and rising value of infrastructure in coastal areas increases 
vulnerability to climate variability and future climate change.
    Water infrastructure, including drinking water and wastewater 
treatment plants, and sewer and stormwater management systems, may be 
at greater risk of flooding, sea level rise and storm surge, low flows, 
and other factors that could impair functioning. For example, some of 
these impacts are already being experienced in Alaska, where rapidly 
melting permafrost has damaged and disrupted drinking water 
distribution systems and wastewater infrastructure.
    Ocean acidification is projected to continue, resulting in the 
reduced biological production of marine calcifiers, including corals.
    Climate change is likely to affect U.S. energy use (e.g., heating 
and cooling requirements), and energy production (e.g., effects on 
hydropower), physical infrastructures and institutional 
infrastructures. Climate change will likely interact with and possibly

[[Page 18903]]

exacerbate ongoing environmental change and environmental pressures in 
settlements, particularly in Alaska where indigenous communities are 
facing major environmental changes from sea ice loss and coastal 
erosion that threaten traditional ways of life.
    Over the 21st century, changes in climate will cause some species 
to shift north and to higher elevations and fundamentally rearrange 
U.S. ecosystems. Differential capacities to adapt to range shifts and 
constraints from development, habitat fragmentation, invasive species, 
and broken ecological connections will alter ecosystem structure, 
composition, function, and services.
    The Administrator acknowledges that as for human health, so too for 
welfare: moderate temperature increases may have some benefits, 
particularly for agriculture and forestry over the short term, as 
summarized above in this section and discussed in more detail in the 
Technical Support Document in Part IV, sections 9(a) and 10(a). This 
possibility is not inconsistent with a judgment that greenhouse gases 
in the atmosphere endanger welfare. Beneficial effects can coexist with 
harmful effects, and it is not necessary to reach a firm conclusion, 
for particular domains and sectors, about the net result in order to 
reach an overall conclusion in favor of endangerment.
5. The Administrator's Consideration of International Effects
    The Administrator judges that the impacts to public health and 
welfare occurring within the U.S. alone warrant her proposed 
endangerment finding. In addition, the Administrator believes that 
consideration of climate change effects in other world regions adds 
support for today's proposal, but that consideration of international 
impacts is not necessary in order to reach a judgment that there is 
endangerment to public health and welfare. Thus, the Administrator does 
not now take a position on the legal question whether international 
effects, on their own, would be sufficient to support an endangerment 
finding. Some of the world's regions are expected to face greater 
impacts due to climate change because they are more vulnerable. Even 
apart from the effects of climate change on other world regions--
effects which are considerable--the Administrator also believes many of 
these impacts could raise economic, trade, humanitarian and even 
national security issues for the U.S.
    The IPCC identifies the most vulnerable world regions as the 
Arctic, because of high rates of projected warming on natural systems; 
Africa, especially the sub-Saharan region, because of current low 
adaptive capacity (e.g., lack of infrastructure and resources) as well 
as climate change; small islands, due to high exposure of population 
and infrastructure to risk of sea-level rise and increased storm surge; 
and Asian mega deltas, due to large populations and high exposure to 
sea level rise, storm surge and river flooding.
    On a global basis, according to the IPCC, projected climate change-
related impacts are likely to affect the health of millions of people, 
particularly those with low adaptive capacity, as a result of a number 
of factors including increased cardio respiratory diseases due to 
higher concentrations of ground-level ozone brought on by higher 
temperatures, and by more frequent and intense heat waves. Food 
production is expected to be much more vulnerable to climate change in 
poorer regions of the world compared to food production in the U.S. The 
IPCC also identified that the coasts around the world are experiencing 
the adverse consequences of hazards related to climate and sea level. 
Coastal settlements are highly vulnerable to extreme events, such as 
storms which impose substantial costs on coastal societies. Ecosystems 
and species around the world are very likely to show a wide range of 
vulnerabilities to climate change, depending on the extent to which 
climate change alters conditions that could cross critical thresholds. 
The most vulnerable ecosystems include coral reefs, sea-ice ecosystems, 
high-latitude boreal forests, and mountain ecosystems where there is no 
possibility of migrating to adapt to climate change.
    Climate change impacts in certain regions of the world may 
exacerbate problems that raise humanitarian, trade and national 
security issues for the U.S. Climate change has been described as a 
potential threat multiplier regarding national security issues. This is 
because, as noted above, climate change can aggravate existing problems 
in certain regions of the world such as poverty, social tensions, 
general environmental degradation, and conflict over increasingly 
scarce water resources.
6. The Administrator's Consideration of Key Uncertainties
    There are many inherent uncertainties associated with 
characterizing both the observed and projected risks and impacts to 
public health and welfare due to current and projected greenhouse gas 
concentrations. Both probability and severity are not easy to specify. 
It is difficult to attribute any single past event (hurricane, flood, 
drought, or heat wave) to elevated greenhouse gas concentrations even 
if it is understood that anthropogenic climate change has already made 
such events more likely or more extreme. The precise rate and magnitude 
of future climate change, for both the globe and for the U.S., remain 
uncertain, even in the hypothetical case where current greenhouse gas 
concentrations would remain constant over the next several decades. 
Projecting the exact magnitude of a particular impact due to climate 
change is difficult due to what are often long time frames to consider, 
the uncertain nature of how the system or sector will be affected by 
climate change, and uncertainties about how other factors (e.g., income 
levels, technologies, demographics) will change over time which can in 
turn affect the vulnerability of the system or sector to climate 
change.
    Many uncertainties could push in the direction of either greater or 
lesser risks as they become better understood. EPA has acknowledged the 
possibility of beneficial effects on both health and welfare. Other 
possibilities include catastrophic events. Examples of such key 
uncertainties involve how the frequency of hurricanes and other extreme 
weather events may change in a changing climate, the potential to 
trigger thresholds for abrupt climate change (e.g., disintegration of 
the Greenland Ice Sheet or collapse of the West Antarctic Ice Sheet), 
and how responsive the climate ultimately will be to the heating effect 
being caused by anthropogenic greenhouse gases. Even if the probability 
of extremely high-impact events may be small, the existence of such 
high impact events, and the potential for other currently unknown 
catastrophic impacts that could plausibly result from record-high 
atmospheric greenhouse gas levels, substantially bolsters the case for 
an endangerment finding with respect to greenhouse gases.\28\ These 
uncertainties will be with us for the foreseeable future. However, 
Congress expected the Administrator to consider uncertainties and 
extrapolate from limited data. It also recognized that there are 
inherent limitations and difficulties in information on public health 
and welfare, but nonetheless expected the

[[Page 18904]]

Administrator to exercise her judgment based on the information 
available.
---------------------------------------------------------------------------

    \28\ A recent economic study that has received considerable 
attention in the climate change research community (Weitzman, The 
Review of Economics and Statistics, 2009) has determined that if the 
probability distribution of the magnitude of possible impacts has a 
``fat tail'', then the expected utility of reducing the probability 
of that tail becomes astronomical. The study determined that 
anthropogenic climate change is a plausible candidate for such a 
``fat tailed'' damage function.
---------------------------------------------------------------------------

    At the same time, there is a broad base of scientific evidence that 
has been reviewed extensively by the scientific community, which 
supports the findings discussed about how anthropogenic increases in 
greenhouse gases are affecting the climate and the key risks to public 
health and welfare that human-induced climate change pose. The 
Administrator believes that the scientific findings in totality provide 
compelling evidence of human-induced climate change, and that serious 
risks and potential impacts to public health and welfare have been 
clearly identified, even if they cannot always be quantified with 
confidence. The Administrator's proposed endangerment finding is based 
on weighing the scientific evidence, considering the uncertainties, and 
balancing any benefits to human health, society and the environment 
that may also occur. Given the evolution of climate change science over 
the past 15 years or more, the Administrator believes the evidence of 
discernible human influence on the global climate, and the risks that 
such climate change poses, has become more compelling, and therefore 
believes the evidence that there is endangerment to the public health 
and welfare of current and future generations has likewise become more 
compelling in step with our increasing understanding of the climate 
change problem.
7. Summary
    The Administrator concludes that, in the circumstances presented 
here, the case for finding that greenhouse gases in the atmosphere 
endanger public health and welfare is compelling and, indeed, 
overwhelming. The scientific evidence described here is the product of 
decades of research by thousands of scientists from the U.S. and around 
the world. The evidence points ineluctably to the conclusion that 
climate change is upon us as a result of greenhouse gas emissions, that 
climatic changes are already occurring that harm our health and 
welfare, and that the effects will only worsen over time in the absence 
of regulatory action. The effects of climate change on public health 
include sickness and death. It is hard to imagine any understanding of 
public health that would exclude these consequences. The effects on 
welfare embrace every category of effect described in the Clean Air 
Act's definition of ``welfare'' and, more broadly, virtually every 
facet of the living world around us. And, according to the scientific 
evidence relied upon in making this finding, the probability of the 
consequences is shown to range from likely to virtually certain to 
occur. This is not a close case in which the magnitude of the harm is 
small and the probability great, or the magnitude large and the 
probability small. In both magnitude and probability, climate change is 
an enormous problem. The greenhouse gases that are responsible for it 
endanger public health and welfare within the meaning of the Clean Air 
Act.

IV. The Administrator's Cause or Contribute Finding

    As noted above, the Administrator has proposed to define the air 
pollution for purposes of the endangerment finding to be the mix of six 
key greenhouse gases in the atmosphere. The Administrator must also 
define the air pollutant or pollutants for purposes of making the cause 
or contribute determination. In this section, the air pollutant(s) that 
may cause or contribute to the proposed definition of air pollution are 
discussed.
    As noted earlier, to help appreciate the distinction between these 
terms, the air pollution can be thought of as the total, cumulative 
stock in the atmosphere. The air pollutants, on the other hand, are the 
emissions and can be thought of as the flow that changes the size of 
the total stock. EPA did not conduct climate modeling analyses to 
determine what fraction of global greenhouse gas concentrations are due 
to the emissions from section 202(a) source categories. Rather, 
consistent with prior practice and with current science, EPA used 
emissions as a perfectly reasonable proxy for contributions to 
atmospheric concentrations. Indeed, cumulative emissions are 
responsible for the cumulative change in the stock of concentrations in 
the atmosphere (i.e., the fraction of a country's or an economic 
sector's cumulative emissions compared to the world's greenhouse gas 
emissions over a long time period will be directly proportional to that 
fraction of the change in concentrations attributable to that country 
or economic sector); likewise, annual emissions are a perfectly 
reasonable proxy for annual incremental changes in atmospheric 
concentrations.

A. The Air Pollutant(s)

    This section discusses the proposed definition of the air pollutant 
for the cause or contribute finding as the collective class of six 
greenhouse gases rather than the individual greenhouse gases.
1. Proposed Definition of Air Pollutant
    When making a cause or contribute finding under section 202(a), the 
Administrator must first look at the emissions from the source category 
and decide how to define the air pollutant being evaluated. In this 
case, the source category emits four gases, which share common physical 
properties relevant to climate change: all are long-lived in the 
atmosphere; all become globally well mixed in the atmosphere; all trap 
outgoing heat that would otherwise escape to space; and all are 
directly emitted as greenhouse gases rather than forming as a 
greenhouse gas in the atmosphere after emission of a pre-cursor gas. 
There are other gases which share these common properties which are not 
emitted by the section 202(a) source categories. Nonetheless, it is 
entirely appropriate for the Administrator to define the air pollutant 
in a manner that recognizes the shared relevant properties of all of 
these six gases, even though they are not all emitted from the source 
category before her.
    The Administrator is proposing to define a single air pollutant 
that is the collective class of the six greenhouse gases. It is the 
Administrator's judgment that this collective approach for the 
contribution test is most consistent with the treatment of greenhouse 
gases by those studying climate change science and policy, where it has 
become common practice to evaluate greenhouse gases on a collective 
CO2-equivalent basis. For example, under the UNFCCC, the 
U.S. and other Parties report their annual emissions of the six 
greenhouse gases in CO2-equivalent units. This facilitates 
comparisons of the multiple greenhouse gases from different sources and 
from different countries, and provides a measure of the collective 
warming potential of multiple greenhouse gases. There are also several 
federal and state climate programs, such as EPA's Climate Leaders 
program and California's Climate Action Registry that encourage firms 
to report (and reduce) emissions of all six greenhouse gases. 
Furthermore, the Administrator recently signed (March 10, 2009) the 
Proposed Greenhouse Gas Mandatory Reporting Rule, which proposes the 
reporting of greenhouse gas emissions on a CO2-equivalent 
basis above certain CO2-equivalent thresholds, thereby also 
recognizing the common and collective treatment of the six greenhouse 
gases.
    This proposed definition of air pollutant is not unique, as EPA has 
previously treated a class of substances with similar impacts on the 
environment as a single pollutant (e.g., particulate matter, volatile 
organic compounds). These six greenhouse gases are being considered 
collectively in the endangerment determination

[[Page 18905]]

because they share the same relevant properties regarding their effect 
on the global climate and the associated changes throughout the climate 
system that can result. Thus, the Administrator believes it is 
appropriate to consider the six greenhouse gases as constituents of a 
single air pollutant.
    The Administrator recognizes that only four of the six greenhouse 
gases covered in the definition of air pollution are emitted by section 
202(a) source categories. It is not unusual for a particular source 
category to emit only a subset of a class of substances that constitute 
a single air pollutant. For example, a source may emit only 20 of the 
possible 200 plus chemicals that meet the definition of volatile 
organic compound (VOC) in the regulations, but that source is evaluated 
based on its emissions of ``VOCs,'' and not its emissions of the 20 
chemicals by name.
    Nonetheless, the Administrator recognizes that each greenhouse gas 
could be considered a separate air pollutant. Thus, although proposing 
to define air pollutant as the class of six greenhouse gases, and 
basing the proposed contribution finding on that air pollutant, the 
Administrator also considered each greenhouse gas individually, as 
discussed below.
2. How the Definition of Air Pollutant in the Endangerment 
Determination Affects Section 202(a) Standards
    The Administrator believes that she has significant discretion when 
establishing greenhouse gas emission standards under section 202(a) 
with respect to whether the greenhouse gases are treated as a single 
collective pollutant or each greenhouse gas is defined as a separate 
air pollutant. Under section 202(a), the Administrator is required to 
set ``standards applicable to the emission of any air pollutant'' that 
the Administrator determines causes or contributes to air pollution 
that endangers. If the Administrator defines the air pollutant as the 
collection of six greenhouse gases, and makes the appropriate cause or 
contribute and endangerment findings for section 202(a) sources, then 
she is called on to set standards applicable to the emission of this 
air pollutant. The term ``standards applicable to the emission of any 
air pollutant'' is not defined, and the Administrator has the 
discretion to interpret it in a reasonable manner to effectuate the 
purposes of section 202(a).
    If the Administrator defines the air pollutant as the group of 
greenhouse gases, she believes she would have the discretion to set 
standards that either control the emissions of the group as a whole, 
and/or standards that control emissions of individual greenhouse gases, 
as constituents of the class. For example, it might be appropriate to 
set a standard that measures and controls the aggregate emissions of 
the group of greenhouse gases, weighted by CO2 equivalent. 
Depending on the circumstances, however, it may be appropriate to set 
standards for individual gases, or some combination of group and 
individual standards. These and other similar approaches could 
appropriately be considered setting a standard or standards applicable 
to the emission of the group of greenhouse gases that are defined as 
the air pollutant. The Administrator would consider a variety of 
factors in determining what approach to take in setting the standard or 
standards; for example she would consider the characteristics of the 
vehicle or engine emissions, such as rate and variability, the kind and 
availability of control technology, and other matters relevant to 
setting standards under section 202(a). Likewise, taking into 
consideration the circumstances involved, the Administrator could 
determine that it was appropriate to set separate standards, a group 
standard, or some combination of those, in a case where each greenhouse 
gas was considered a separate air pollutant.\29\
---------------------------------------------------------------------------

    \29\ At this time, a final positive endangerment finding would 
not make the air pollutant found to cause or contribute to air 
pollution that endangers a regulated pollutant under the CAA's 
Prevention of Significant Deterioration (PSD) program. See 
memorandum entitled ``EPA's Interpretation of Regulations that 
Determine Pollutants Covered By Federal Prevention of Significant 
Deterioration (PSD) Permit Program'' (Dec. 18, 2008). EPA is 
reconsidering this memorandum and will be seeking public comment on 
the issues raised in it. That proceeding, not this rulemaking, would 
be the appropriate venue for submitting comments on the issue of 
whether a final, positive endangerment finding under section 202(a) 
of the Act should trigger the PSD program, and the implications of 
the definition of air pollutant in that endangerment finding on the 
PSD program.
---------------------------------------------------------------------------

B. Proposed Cause or Contribute Finding

1. Overview of Greenhouse Gas Emissions
    In 2006, U.S. greenhouse gas emissions were 7,054 teragrams \30\ of 
CO2 equivalent \31\ (TgCO2eq). The dominant gas 
emitted is CO2, mostly from fossil fuel combustion. Methane 
is the second largest component of U.S. emissions, followed by 
N2O, and the fluorinated gases (HFCs, PFCs, and 
SF6). Electricity generation is the largest emitting sector 
(2,378 TgCO2eq or 34 percent of total U.S. greenhouse gas 
emissions), followed by transportation (1,970 TgCO2eq or 28 
percent) and industry (1,372 TgCO2eq or 19 percent). Land 
use, land use change and forestry offset almost 13 percent of total 
U.S. emissions through net sequestration. Total U.S. greenhouse gas 
emissions have increased by almost 15 percent between 1990 and 2006. 
The electricity generation and transportation sectors have contributed 
most to this increase.
---------------------------------------------------------------------------

    \30\ One teragram (Tg) = 1 million metric tons. 1 metric ton = 
1,000 kg = 1.102 short tons = 2,205 lbs.
    \31\ \\ Long-lived greenhouse gases are compared and summed 
together on a CO2 equivalent basis by multiplying each 
gas by its Global Warming Potential (GWPs), as estimated by IPCC. In 
accordance with UNFCCC reporting procedures, the U.S. quantifies 
greenhouse gas emissions using the 100-year time frame values for 
GWPs established in the IPCC Second Assessment Report.
---------------------------------------------------------------------------

    Total global greenhouse gas emissions in 2005 (the most recent year 
for which data for all countries and all greenhouse gases are 
available) were 38,726 TgCO2eq. This represents an increase 
in global greenhouse gas emissions of about 26 percent since 1990 
(excluding land use, land use change and forestry). In 2005, total U.S. 
greenhouse gas emissions were responsible for 18 percent of global 
emissions, ranking only behind China, which was responsible for 19 
percent of global greenhouse gas emissions.
2. Overview of Section 202(a) Source Categories and Cause or Contribute 
Analysis
    The relevant mobile sources under section 202 (a)(1) of the Clean 
Air Act are ``any class or classes of new motor vehicles or new motor 
vehicle engines, * * * .'' CAA Sec.  202(a)(1) (emphasis added). The 
motor vehicles and motor vehicle engines (hereinafter ``Section 202(a) 
source categories'') addressed are:

 Passenger cars
 Light-duty trucks
 Motorcycles
 Buses
 Medium/heavy-duty trucks

    As noted earlier, in the past the requisite contribution findings 
have been proposed concurrently with proposing emission standards for 
the relevant mobile source category. Thus, the prior contribution 
findings often focused on a subset of the section 202(a) (or other 
section) source categories. Today's proposed cause or contribute 
finding, however, is for all of the section 202(a) source categories 
and the Administrator is considering emissions from all of these source 
categories in the proposed determination.
    Sources covered by section 202(a) of the Act emit four of the six 
greenhouse gases that in combination comprise the air pollutant being 
considered in the cause or contribute analysis: Carbon

[[Page 18906]]

dioxide, methane, nitrous oxide, and hydrofluorocarbons.\32\ To support 
the Administrator's assessment, EPA has analyzed historical data of 
these greenhouse gases for motor vehicles and motor vehicle engines in 
the U.S. from 1990 to 2006. The source of the U.S. greenhouse gas 
emissions data is the Inventory of U.S. Greenhouse Gas Emissions and 
Sinks: 1990-2006, published in 2008 (hereinafter ``U.S. Inventory''). 
The source of global greenhouse gas emissions data, against which a 
number of comparisons are made, is the Climate Analysis Indicators Tool 
of the World Resources Institute (2007).\33\
---------------------------------------------------------------------------

    \32\ \\ Emissions of hydrofluorocarbons result from the use of 
HFCs in cooling systems designed for passenger comfort, as well as 
auxiliary systems for refrigeration.
    \33\ WRI (2007) Climate Analysis Indicators Tool (CAIT). 
Available at http://cait.wri.org. Accessed February 20, 2009.
---------------------------------------------------------------------------

    There are a number of possible ways of assessing ``cause or 
contribute'' and no single approach is required or has been used 
exclusively in previous determinations under the Act. Because the air 
pollution against which the contribution is being evaluated is the mix 
of six greenhouse gas concentrations, the logical starting point for 
any contribution analysis is a comparison of the emissions of the air 
pollutant from the section 202(a) category to the total, global 
emissions of the six greenhouse gases. The Administrator recognizes 
that there are other valid comparisons that can and should be 
considered in evaluating whether emissions of the air pollutant cause 
or contribute to the combined concentration of the six greenhouse 
gases. To inform the Administrator's assessment, the following types of 
comparisons for both the collective and individual emissions of 
greenhouse gases from section 202(a) source categories are provided:
     As a share of total current global aggregate emissions of 
the six greenhouse gases included in the proposed definition of air 
pollution;
     As a share of total current U.S. aggregate emissions of 
the six greenhouse gases; and
     As a share of the total current global transportation 
emissions of the six greenhouse gases.
    In addition, when reviewing each greenhouse gas as an individual 
pollutant, the Administrator also considered the following comparisons:
     As a share of current global emissions of that individual 
greenhouse gas;
     As a share of total section 202(a) source category 
emissions of the six greenhouse gases; and
     As a share of current U.S. emissions of that individual 
greenhouse gas, including comparisons to the magnitude of emissions of 
that greenhouse gas from other non-transport related source categories.
    Note that for global comparisons, all emissions are from the year 
2005, the most recent year for which data for all greenhouse gas 
emissions and all countries are available. For comparisons within the 
U.S., all emissions are for the year 2006, the most recent year for 
which U.S. data are currently available. All values for emission 
numbers represent total annual emissions. All annual emissions data are 
being considered on a CO2 equivalent basis, which is a 
commonly accepted metric for comparing different greenhouse gases, both 
in the U.S. annual greenhouse gas Inventory and with international 
greenhouse gas inventories from other Parties to the UNFCCC.\34\ Future 
projected emissions are not used in this cause or contribute analysis, 
because they are uncertain and current emissions data are a valid proxy 
for near-term emissions. This approach is consistent with how 
contribution has been assessed in previous actions under the Clean Air 
Act.
---------------------------------------------------------------------------

    \34\ Emissions of different greenhouse gases are compared using 
global warming potentials (GWPs). The GWP of a greenhouse gas is 
defined as the ratio of the time-integrated radiative forcing from 
the instantaneous release of 1 kilogram (kg) of a trace substance 
relative to that of 1 kg of a reference gas (IPCC 2001). The 
reference gas used is CO2, and therefore GWP-weighted 
emissions are measured in teragrams of CO2 equivalent 
(TgCO2eq.).
---------------------------------------------------------------------------

    Some comments on the ANPR argued that when evaluating the 
contribution from new motor vehicles and engines, the Administrator 
needs to project what emissions would be after implementation of the 
fuel efficiency standards in the Energy Independence and Security Act 
of 2007 (EISA). Other comments noted that the Administrator should 
recognize that in the future the denominator of global aggregate 
emissions of greenhouse gases will increase as the numerator of new 
motor vehicle and engine emissions decreases. As noted above, the 
Administrator believes that the traditional practice of considering the 
recent motor vehicle emissions inventory as a surrogate for estimates 
for new motor vehicles and engines is appropriate. In general, the 
focus of the contribution test should be on current and near-term 
emissions. The current and near term emissions from the section 202(a) 
sources can be expected to impact atmospheric concentrations for many 
decades to come, given the long atmospheric life of the greenhouse 
gases. The Administrator is aware of the requirements of EISA, and she 
has concluded that the expected reductions in emissions from section 
202(a) source categories would not affect her determination regarding 
cause or contribution. In addition to looking at absolute emissions 
comparisons, the Administrator also considered other relevant factors, 
as described below.
3. Proposed Finding That Emissions of the Collective Group of Six 
Greenhouse Gases Contributes to Air Pollution Which May Reasonably Be 
Anticipated To Endanger Public Health and Welfare
a. Total Greenhouse Gas Emissions From Section 202(a) Source Categories
    As discussed above, the Administrator is proposing to define air 
pollutant for purposes of the contribution finding as the collective 
group of six greenhouse gases. Section 202(a) source categories emit 
four of the greenhouse gases (CO2, CH4, 
N2O, and HFCs), therefore the emissions of the single air 
pollutant are the collective emissions of these four greenhouse gases. 
This section summarizes information on total section 202(a) source 
category emissions of greenhouse gases within that definition.\35\
---------------------------------------------------------------------------

    \35\ Detailed combined greenhouse gas emissions data for Section 
202(a) source categories are presented in Appendix B of the 
Technical Support Document.
---------------------------------------------------------------------------

    In 2006, section 202(a) source categories collectively were the 
second largest greenhouse gas-emitting sector within the U.S. (behind 
the electricity generating sector), emitting 1,665 TgCO2eq 
and representing 24 percent of total U.S. greenhouse gas emissions 
(Table 1). Between 1990 and 2006, total greenhouse gas emissions from 
passenger cars decreased 0.9 percent, while emissions from light-duty 
trucks increased 57 percent, largely due to the increased use of sport-
utility vehicles and other light-duty trucks.
    Globally in 2005, section 202(a) source category greenhouse gas 
emissions represented 28 percent of global transport greenhouse gas 
emissions and 4.3 percent of total global greenhouse gas emissions 
(Table 2). The global transport sector was 14 percent of all global 
greenhouse gas emissions in 2005. If U.S. section 202(a) source 
category greenhouse gas emissions were ranked against total greenhouse 
gas emissions for entire countries, U.S. section 202(a) emissions would 
rank behind only China, the U.S. as a whole, Russia and India, and 
would rank ahead

[[Page 18907]]

of Japan, Brazil, Germany and every other country in the world.

                                   Table 1--Sectoral Comparison to Total U.S. Greenhouse Gas (GHG) Emissions (TgCO2e)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                    U.S. Emissions                        1990       1995       2000       2001       2002       2003       2004       2005       2006
--------------------------------------------------------------------------------------------------------------------------------------------------------
Section 202(a) GHG emissions.........................     1231.9     1364.4     1568.1     1576.8     1617.9     1629.7     1667.4     1670.0     1665.4
    Share of U.S. (%)................................      20.0%      21.0%      22.3%      22.8%      23.2%      23.3%      23.6%      23.4%      23.6%
Electricity Sector emissions.........................     1859.1     1989.7     2328.9     2290.9     2300.4     2329.4     2363.4     2430.0     2377.8
    Share of U.S. (%)................................      30.2%      30.6%      33.1%      33.1%      33.0%      33.3%      33.4%      34.1%      33.7%
Industrial Sector emissions..........................     1460.3     1478.0     1432.9     1384.3     1384.9     1375.5     1388.9     1354.3     1371.5
    Share of U.S. (%)................................      23.8%      22.8%      20.4%      20.0%      19.8%      19.7%      19.6%      19.0%      19.4%
                                                      --------------------------------------------------------------------------------------------------
        Total US GHG emissions.......................     6148.3     6494.0     7032.6     6921.3     6981.2     6998.2     7078.0     7129.9     7054.2
--------------------------------------------------------------------------------------------------------------------------------------------------------


  Table 2--Comparison to Global Greenhouse Gas (GHG) Emissions (TgCO2e)
------------------------------------------------------------------------
                                                                   Sec
                                                          2005    202(a)
                                                                  share
------------------------------------------------------------------------
All US GHG emissions..................................    7,130    23.4%
Global transport GHG emissions........................    5,909    28.3%
All global GHG emissions..............................   38,726     4.3%
------------------------------------------------------------------------

b. Proposed Contribution Finding for the Single Air Pollutant Comprised 
of the Collective Group of Six Greenhouse Gases
    Based on the data summarized above, the Administrator proposes to 
find that the emissions of the defined air pollutant from new motor 
vehicles and engines contribute to the air pollution previously 
discussed. As noted above, the Administrator recognizes that only four 
of the six greenhouse gases covered in the definition of air pollution 
are emitted by section 202(a) source categories, and has made her 
determination based on the combined contribution of these four 
greenhouse gases. It is not unusual for a particular source category to 
emit only a subset of a class of substances that constitute a single 
air pollutant (for example, volatile organic compounds).
    It is the Administrator's judgment that the collective greenhouse 
gas emissions from section 202(a) source categories are significant, 
whether the comparison is global (over 4 percent of total greenhouse 
gas emissions) or domestic (24 percent of total greenhouse gas 
emissions). The Administrator believes that consideration of the global 
context is important for the cause or contribute test but that the 
analysis should not solely consider the global context. Greenhouse gas 
emissions from section 202(a) source categories, or from any other U.S. 
source, will become globally mixed in the atmosphere, and thus will 
have an effect not only on the U.S. regional climate but on the global 
climate as a whole, and indeed for years and decades to come. The 
Administrator believes that these unique, global aspects of the climate 
change problem tend to support a finding that lower levels of emissions 
should be considered to contribute to the air pollution than might 
otherwise be considered appropriate when considering contribution to a 
local or regional air pollution problem.
    Importantly, because no single greenhouse gas source category 
dominates on the global scale, many (if not all) individual greenhouse 
gas source categories could appear too small to matter, when, in fact, 
they could be very significant contributors in terms of both absolute 
emissions or in comparison to other similar source categories within 
the U.S. If the U.S. and the rest of the world are to combat the risks 
associated with global climate change, contributors must do their part 
even if their contributions to the global problem, measured in terms of 
percentage, are smaller than typically encountered when tackling solely 
regional or local environmental issues. Total U.S. greenhouse gas 
emissions make up about 18 percent of the world's greenhouse gas 
emissions, and individual sources within the U.S. will be subsets of 
that 18 percent. The Administrator is placing significant weight on the 
fact that section 202(a) source categories contribute to 24 percent of 
total U.S. greenhouse gas emissions for the proposed contribution 
finding.
4. Additional Consideration of Whether Each Greenhouse Gas as a 
Separate Air Pollutant Contributes to Air Pollution Which May 
Reasonably Be Anticipated To Endanger Public Health and Welfare
    As noted above, the Administrator also considered whether emissions 
of individual greenhouse gas from section 202(a) source categories, 
separately, would contribute to the air pollution defined above. This 
section discussed the contribution of each of the four individual 
greenhouse gases emitted by Section 202(a) source categories.
a. Carbon Dioxide Emissions From Section 202(a) Source Categories
    Carbon dioxide is emitted from motor vehicles and motor vehicle 
engines during the fossil fuel combustion process. During combustion, 
the carbon stored in the fuels is oxidized and emitted as 
CO2 and smaller amounts of other carbon compounds.
    In 1990, Section 202(a) source categories emitted 23 percent of 
total U.S. CO2 emissions, behind only the electricity 
generation sector (36 percent). In 2006, Section 202(a) source 
categories remained the second largest sector, growing to 26 percent of 
total U.S. CO2 emissions.
    Carbon dioxide is the dominant greenhouse gas emitted from Section 
202(a) source categories (94 percent of total U.S. Section 202(a) 
source category greenhouse gas emissions in 2006). Carbon dioxide 
emissions from these source categories grew by 32 percent between 1990 
and 2006, largely due to increased carbon dioxide emissions from light-
duty trucks (61 percent since 1990) and medium/heavy-duty trucks (76 
percent).
    In 2005, carbon dioxide from section 202(a) source categories in 
the U.S. were responsible for 4 percent of global aggregate greenhouse 
gas emissions (a similar percentage compared to the U.S. share of 
global greenhouse gas emissions when considering all greenhouse gas 
emissions from U.S. section 202(a) sources). Section 202(a) source 
category carbon dioxide emissions are a significantly larger share of 
global transportation greenhouse gas emissions (27 percent) than the 
corresponding share of all U.S. CO2 emissions to the global 
total (18 percent), reflecting the comparatively larger size of the 
transport sector in the U.S. compared to the global average.
    If the Administrator were to evaluate carbon dioxide as a separate 
air pollutant, she would consider the

[[Page 18908]]

emissions from section 202(a) source categories to contribute to the 
air pollution, placing primary weight on the fact that carbon dioxide 
is so dominant among all section 202(a) greenhouse gas emissions (94 
percent) and contributes to a significant share of all U.S. carbon 
dioxide emissions (26 percent) and global greenhouse gas emissions (4 
percent).
b. Methane Emissions From Section 202(a) Source Categories
    Methane emissions from motor vehicles are a function of the methane 
content of the motor fuel, the amount of hydrocarbons passing 
uncombusted through the engine, and any post-combustion control of 
hydrocarbon emissions (such as catalytic converters).
    In 2006, methane emissions from section 202(a) source categories 
were 0.11 percent of total greenhouse gas emissions from U.S. motor 
vehicles and motor vehicle engines. Methane emissions from these source 
categories decreased by 58 percent between 1990 and 2006, largely due 
to decreased methane emissions from passenger cars (62 percent) and 
light-duty trucks (51 percent). In 2006, methane emissions from these 
source categories equaled 0.32 percent of total U.S. methane emissions 
and 0.03 percent of total U.S. greenhouse gas emissions.
    Methane emissions from Section 202(a) source categories were less 
than 0.01 percent of total global greenhouse gas emissions in 2005. 
When compared to the smaller subsets of global transportation 
emissions, and global methane emissions, section 202(a) source category 
methane emissions were about 0.03 percent in both cases in 2005.
    If the Administrator were to evaluate methane as a separate air 
pollutant, she would consider the emissions from section 202(a) source 
categories to contribute to the air pollution. The Administrator would 
place primary weight on the same reason that the Administrator promotes 
the reduction of methane and other non-CO2 greenhouse gas 
emissions from sources with relatively low but potent emissions, as 
manifested in its domestic methane partnership programs and 
the international Methane to Markets Partnership, which was launched in 
2004. Specifically, these emissions are at a level that contributes to 
the climate change problem and there are valuable reductions available 
from these levels. As noted above, consideration of the global nature 
of greenhouse gas emissions and climate change means that a percentage 
contribution of specific gases and sectors would be expected to be much 
smaller than for previous rulemakings when the nature of the air 
pollution was national, regional or local.
c. Nitrous Oxide Emissions From Section 202(a) Source Categories
    Nitrous oxide is a product of the reaction that occurs between 
nitrogen and oxygen during fuel combustion. Nitrous oxide (and nitrogen 
oxide (NOX)) emissions from motor vehicles and motor vehicle 
engines are closely related to fuel characteristics, air-fuel mixes, 
combustion temperatures, and the use of pollution control equipment. 
For example, some types of catalytic converters installed to reduce 
motor vehicle NOX, CO, and hydrocarbon emissions can promote 
the formation of nitrous oxide.
    In 2006, nitrous oxide emissions from section 202(a) source 
categories accounted for 1.8 percent of total greenhouse gas emissions 
from U.S. motor vehicles and motor vehicle engines. Nitrous oxide 
emissions from these source categories decreased by 27 percent between 
1990 and 2006, largely due to decreased emissions from passenger cars 
(39 percent) and light-duty trucks (10 percent). In 2006, nitrous oxide 
emissions from these source categories equaled 8.0 percent of total 
U.S. nitrous oxide emissions. In fact, Section 202(a) source categories 
are the second largest U.S source of N2O, behind only 
agricultural soil management (which represented 72 percent of total 
nitrous oxide emissions in 2006).
    In 2005, nitrous oxide emissions from U.S. section 202(a) source 
categories were 0.08 percent of total global greenhouse gas emissions. 
Also in 2005, U.S. section 202(a) sources accounted for 1.0 percent of 
global N2O emissions and 0.6 percent of global 
transportation greenhouse gas emissions.
    If the Administrator were to evaluate nitrous oxide as a separate 
air pollutant, she would consider the emissions from section 202(a) 
source categories to contribute to the air pollution, placing primary 
weight on the fact that nitrous oxide emissions from section these 
source categories are significant in terms of their contribution to 
U.S. (and global) emissions of that particular gas. Although Section 
202 emissions of nitrous oxide appear small on a global basis, they 
were 8.0 percent of total U.S. N2O emissions in 2006, second 
only to agricultural soil management (which represented 72 percent of 
total nitrous oxide emissions in 2006). In addition, as mentioned in 
the previous discussion of methane, given the vast number of sources 
and sectors that emit greenhouse gases around the world, even sources 
which represent a small percentage of U.S. or global emissions can be 
considered to contribute to the larger problem.
d. HFC Emissions From Section 202(a) Source Categories
    Hydrofluorocarbons (a term which encompasses a group of eleven 
related compounds) are progressively replacing CFCs and HCFCs in 
section 202(a) cooling and refrigeration systems as they are being 
phased out under the Montreal Protocol and Title VI of the Clean Air 
Act. For example, HFC-134a has become a replacement for CFC-12 in 
mobile air conditioning systems. A number of HFC blends, containing 
multiple compounds, have also been introduced. The emissions pathway 
can be complex, with hydrofluorocarbons being emitted to the atmosphere 
during charging of cooling and refrigeration systems, during operation, 
and during decommissioning and disposal.
    Section 202(a) source categories of hydrofluorocarbons accounted 
for 4.2 percent of total greenhouse gas emissions from U.S. motor 
vehicles and motor vehicle engines in 2006. Hydrofluorocarbons were not 
used in motor vehicles in 1990, but by 2006 emissions had increased to 
70 TgCO2e (this represents an increase of 270 percent 
between 1995 and 2006). In 2006, hydrofluorocarbon emissions from these 
source categories equaled 56 percent of total U.S. hydrofluorocarbon 
emissions, making it the single largest source category of U.S. 
hydrofluorocarbon emissions.
    In 2005, hydrofluorocarbons from section 202(a) source categories 
were 0.18 percent of total global greenhouse gas emissions. When 
compared to the smaller subset of global transportation emissions, 
section 202(a) source category hydrofluorocarbon emissions were 1.3 
percent in 2005. However, U.S. section 202(a) HFC sources equaled 18 
percent of global hydrofluorocarbon emissions, making it the largest 
source of global hydrofluorocarbon emissions.
    If the Administrator were to evaluate hydrofluorocarbons as a 
separate air pollutant, she would consider the emissions from section 
202(a) source categories to contribute to the air pollution, placing 
primary weight on the fact that hydrofluorocarbon emissions from these 
source categories are the largest U.S. and global source of that 
particular gas, and emissions have grown 270 percent since 1995. If the 
decision were made that these emissions do not contribute because 
hydrofluorocarbon emissions under section 202(a) make up just 0.18 
percent

[[Page 18909]]

of global greenhouse gas emissions it would be inconsistent with the 
U.S. practice of encouraging hydrofluorocarbon emission reductions. 
Indeed, if the Administrator determined that hydrofluorocarbon 
emissions from section 202(a) source categories did not contribute, it 
would be unlikely that she would find contribution for 
hydrofluorocarbons from any other source of these (and other 
fluorinated) greenhouse gases. For these reasons, the Administrator 
believes the global context remains important to consider, but that 
more weight should placed on a contribution analysis done within the 
domestic context.

V. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

    Under Executive Order (EO) 12866 (58 FR 51735, October 4, 1993), 
this action is a ``significant regulatory action'' because it raises 
novel policy issues. Accordingly, EPA submitted this action to the 
Office of Management and Budget (OMB) for review under EO 12866 and any 
changes made in response to OMB recommendations have been documented in 
the docket for this action.

B. Paperwork Reduction Act

    This action does not impose an information collection burden under 
the provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. 
Burden is defined at 5 CFR 1320.3(b). The final endangerment finding 
would not impose an information collection request on any person.

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency 
to prepare a regulatory flexibility analysis of any rule subject to 
notice and comment rulemaking requirements under the Administrative 
Procedure Act or any other statute unless the agency certifies that the 
rule will not have a significant economic impact on a substantial 
number of small entities. Small entities include small businesses, 
small organizations, and small governmental jurisdictions.
    For purposes of assessing the impacts of this action on small 
entities, small entity is defined as: (1) A small business as defined 
by the Small Business Administration's (SBA) regulations at 13 CFR 
121.201; (2) a small governmental jurisdiction that is a government of 
a city, county, town, school district or special district with a 
population of less than 50,000; and (3) a small organization that is 
any not-for-profit enterprise which is independently owned and operated 
and is not dominant in its field.
    Because this proposed action will not impose any requirements, the 
Administrator certifies that this proposed action will not have a 
significant economic impact on a substantial number of small entities. 
This proposed action will not impose any requirements on small 
entities. The endangerment and contribution findings do not in-and-of-
themselves impose any new requirements but rather set forth the 
Administrator's determination on whether greenhouse gases in the 
atmosphere may reasonably be anticipated to endanger public health or 
welfare, and whether emissions of greenhouse gases from new motor 
vehicles and engines contribute to this air pollution. Accordingly, the 
proposed action affords no opportunity for EPA to fashion for small 
entities less burdensome compliance or reporting requirements or 
timetables or exemptions from all or part of the proposal.

D. Unfunded Mandates Reform Act

    This action contains no Federal mandates under the provisions of 
Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), 2 U.S.C. 
1531-1538 for State, local, or tribal governments or the private 
sector. The action imposes no enforceable duty on any State, local or 
tribal governments or the private sector. Therefore, this action is not 
subject to the requirements of sections 202 or 205 of the UMRA.
    This action is also not subject to the requirements of section 203 
of UMRA because it contains no regulatory requirements that might 
significantly or uniquely affect small governments.

E. Executive Order 13132: Federalism

    Executive Order 13132, entitled ``Federalism'' (64 FR 43255, August 
10, 1999), requires EPA to develop an accountable process to ensure 
``meaningful and timely input by State and local officials in the 
development of regulatory policies that have federalism implications.'' 
``Policies that have federalism implications'' is defined in the 
Executive Order to include regulations that have ``substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government.''
    This proposed endangerment determination does not have federalism 
implications. It will not have substantial direct effects on the 
States, on the relationship between the national government and the 
States, or on the distribution of power and responsibilities among the 
various levels of government, as specified in Executive Order 13132. 
Thus, Executive Order 13132 does not apply to this rule.

F. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    This action does not have tribal implications, as specified in 
Executive Order 13175 (65 FR 67249, November 9, 2000). Thus, Executive 
Order 13175 does not apply to this action.

G. Executive Order 13045: Protection of Children From Environmental 
Health Risks and Safety Risks

    EPA interprets EO 13045 (62 FR 19885, April 23, 1997) as applying 
only to those regulatory actions that concern health or safety risks, 
such that the analysis required under section 5-501 of the EO has the 
potential to influence the regulation. This action is not subject to EO 
13045 because it does not establish an environmental standard intended 
to mitigate health or safety risks. Although the Administrator 
considered health and safety risks as part of this proposed 
endangerment finding, the proposed finding itself does not impose a 
standard intended to mitigate those risks.

H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use

    This action is not a ``significant energy action'' as defined in 
Executive Order 13211 (66 FR 28355 (May 22, 2001)), because it is not 
likely to have a significant adverse effect on the supply, 
distribution, or use of energy. This action does not impose 
requirements on these activities.

I. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (``NTTAA''), Public Law 104-113, 12(d) (15 U.S.C. 272 note) 
directs EPA to use voluntary consensus standards in its regulatory 
activities unless to do so would be inconsistent with applicable law or 
otherwise impractical. Voluntary consensus standards are technical 
standards (e.g., materials specifications, test methods, sampling 
procedures, and business practices) that are developed or adopted by 
voluntary consensus standards bodies. NTTAA directs EPA to provide 
Congress, through OMB, explanations when the Agency decides not to use

[[Page 18910]]

available and applicable voluntary consensus standards.
    This proposed rulemaking does not involve technical standards. 
Therefore, EPA is not considering the use of any voluntary consensus 
standards.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    Executive Order (EO) 12898 (59 FR 7629 (Feb. 16, 1994)) establishes 
federal executive policy on environmental justice. Its main provision 
directs federal agencies, to the greatest extent practicable and 
permitted by law, to make environmental justice part of their mission 
by identifying and addressing, as appropriate, disproportionately high 
and adverse human health or environmental effects of their programs, 
policies, and activities on minority populations and low-income 
populations in the United States.
    EPA has determined that this proposed endangerment determination 
will not have disproportionately high and adverse human health or 
environmental effects on minority or low-income populations. 
Nonetheless, when developing the proposed endangerment determination, 
the Administrator considered the impacts of climate change on minority 
or low-income populations.

    Dated: April 17, 2009.
Lisa P. Jackson,
Administrator.
[FR Doc. E9-9339 Filed 4-23-09; 8:45 am]
BILLING CODE 6560-50-P