[Federal Register: December 15, 2009 (Volume 74, Number 239)]
[Rules and Regulations]
[Page 66495-66546]
[DOCID:fr15de09-19]

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Part V

Environmental Protection Agency

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40 CFR Chapter I

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

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Chapter I

[EPA-HQ-OAR-2009-0171; FRL-9091-8]
RIN 2060-ZA14

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

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Administrator finds that six greenhouse gases taken in
combination endanger both the public health and the public welfare of
current and future generations. The Administrator also finds that the
combined emissions of these greenhouse gases from new motor vehicles
and new motor vehicle engines contribute to the greenhouse gas air
pollution that endangers public health and welfare under CAA section
202(a). These Findings are based on careful consideration of the full
weight of scientific evidence and a thorough review of numerous public
comments received on the Proposed Findings published April 24, 2009.

DATES: These Findings are effective on January 14, 2010.

ADDRESSES: EPA has established a docket for this action under Docket ID
No. EPA-HQ-OAR-2009-0171. All documents in the docket are listed on the
www.regulations.gov Web site. Although listed in the index, some
information is not publicly available, e.g., confidential business
information (CBI) or other information whose disclosure is restricted
by statute. Certain other material, such as copyrighted material, is
not placed on the Internet and will be publicly available only in hard
copy form. Publicly available docket materials are available either
electronically through www.regulations.gov or in hard copy at EPA's
Docket Center, Public Reading Room, EPA West Building, Room 3334, 1301
Constitution Avenue, NW., Washington, DC 20004. 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:<PHONE_NUMBER>; fax number:<PHONE_NUMBER>; e-mail
address<EMAIL_ADDRESS>For additional information regarding
these Findings, please go to the Web site http://www.epa.gov/
climatechange/endangerment.html.

SUPPLEMENTARY INFORMATION:

Judicial Review

    Under CAA section 307(b)(1), judicial review of this final action
is available only by filing a petition for review in the U.S. Court of
Appeals for the District of Columbia Circuit by February 16, 2010.
Under CAA section 307(d)(7)(B), only an objection to this final action
that was raised with reasonable specificity during the period for
public comment can be raised during judicial review. This section also
provides a mechanism for us to convene a proceeding for
reconsideration, `` `[i]f the person raising an objection can
demonstrate to EPA that it was impracticable to raise such objection
within [the period for public comment] or if the grounds for such
objection arose after the period for public comment (but within the
time specified for judicial review) and if such objection is of central
relevance to the outcome of this rule.' '' Any person seeking to make
such a demonstration to us should submit a Petition for Reconsideration
to the Office of the Administrator, Environmental Protection Agency,
Room 3000, Ariel Rios Building, 1200 Pennsylvania Ave., NW.,
Washington, DC 20004, with a copy to the person listed in the preceding
FOR FURTHER INFORMATION CONTACT section, and the Associate General
Counsel for the Air and Radiation Law Office, Office of General Counsel
(Mail Code 2344A), Environmental Protection Agency, 1200 Pennsylvania
Ave., NW., Washington, DC 20004.
    Acronyms and Abbreviations. The following acronyms and
abbreviations are used in this document.

ACUS Administrative Conference of the United States
ANPR Advance Notice of Proposed Rulemaking
APA Administrative Procedure Act
CAA Clean Air Act
CAFE Corporate Average Fuel Economy
CAIT Climate Analysis Indicators Tool
CASAC Clean Air Scientific Advisory Committee
CBI Confidential Business Information
CCSP Climate Change Science Program
CFCs chlorofluorocarbons
CFR Code of Federal Regulations
CH4 methane
CO2 carbon dioxide
CO2e CO2-equivalent
CRU Climate Research Unit
DOT U.S. Department of Transportation
EO Executive Order
EPA U.S. Environmental Protection Agency
FR Federal Register
GHG greenhouse gas
GWP global warming potential
HadCRUT Hadley Centre/Climate Research Unit (CRU) temperature record
HCFCs hydrochlorofluorocarbons
HFCs hydrofluorocarbons
IA Interim Assessment report
IPCC Intergovernmental Panel on Climate Change
MPG miles per gallon
MWP Medieval Warm Period
N2O nitrous oxide
NAAQS National Ambient Air Quality Standards
NAICS North American Industry Classification System
NASA National Aeronautics and Space Administration
NF3 nitrogen trifluoride
NHTSA National Highway Traffic Safety Administration
NOAA National Oceanic and Atmospheric Administration
NOI Notice of Intent
NOX nitrogen oxides
NRC National Research Council
NSPS new source performance standards
NTTAA National Technology Transfer and Advancement Act of 1995
OMB Office of Management and Budget
PFCs perfluorocarbons
PM particulate matter
PSD Prevention of Significant Deterioration
RFA Regulatory Flexibility Act
SF6 sulfur hexafluoride
SIP State Implementation Plan
TSD technical support document
U.S. United States
UMRA Unfunded Mandates Reform Act of 1995
UNFCCC United Nations Framework Convention on Climate Change
USGCRP U.S. Global Climate Research Program
VOC volatile organic compound(s)
WCI Western Climate Initiative
WRI World Resources Institute

TABLE OF CONTENTS

I. Introduction
    A. Overview
    B. Background Information Helpful To Understand These Findings
    1. Greenhouse Gases and Transportation Sources Under CAA Section
202(a)
    2. Joint EPA and Department of Transportation Proposed
Greenhouse Gas Rule
    C. Public Involvement
    1. EPA's Initial Work on Endangerment
    2. Public Involvement Since the April 2009 Proposed Endangerment
Finding
    3. Issues Raised Regarding the Rulemaking Process
II. Legal Framework for This Action
    A. Section 202(a) of the CAA--Endangerment and Cause or
Contribute
    1. The Statutory Framework
    2. Summary of Response to Key Legal Comments on the
Interpretation of the CAA Section 202(a) Endangerment and Cause or
Contribute Test

    B. Air Pollutant, Public Health and Welfare
III. EPA's Approach for Evaluating the Evidence Before It
    A. The Science on Which the Decisions Are Based
    B. The Law on Which the Decisions Are Based
    C. Adaptation and Mitigation
    D. Geographic Scope of Impacts
    E. Temporal Scope of Impacts
    F. Impacts of Potential Future Regulations and Processes that
Generate Greenhouse Gas Emissions
IV. The Administrator's Finding That Emissions of Greenhouse Gases
Endanger Public Health and Welfare
    A. The Air Pollution Consists of Six Key Greenhouse Gases
    1. Common Physical Properties of the Six Greenhouse Gases
    2. Evidence That the Six Greenhouse Gases Are the Primary Driver
of Current and Projected Climate Change
    3. The Six Greenhouse Gases Are Currently the Common Focus of
the Climate Change Science and Policy Communities
    4. Defining Air Pollution as the Aggregate Group of Six
Greenhouse Gases Is Consistent With Evaluation of Risks and Impacts
Due to Human-Induced Climate Change
    5. Defining the Air Pollution as the Aggregate Group of Six
Greenhouse Gases Is Consistent With Past EPA Practice
    6. Other Climate Forcers Not Being Included in the Definition of
Air Pollution for This Finding
    7. Summary of Key Comments on Definition of Air Pollution
    B. The Air Pollution Is Reasonably Anticipated To Endanger Both
Public Health and Welfare
    1. The Air Pollution Is Reasonably Anticipated To Endanger
Public Health
    2. The Air Pollution Is Reasonably Anticipated To Endanger
Public Welfare
V. The Administrator's Finding That Greenhouse Gases From CAA
Section 202(a) Sources Cause or Contribute to the Endangerment of
Public Health and Welfare
    A. The Administrator's Definition of the ``Air Pollutant''
    B. The Administrator's Finding Whether Emissions of the Air
Pollutant From Section 202(a) Source Categories Cause or Contribute
to the Air Pollution That May Be Reasonably Anticipated To Endanger
Public Health and Welfare
    C. Response to Key Comments on the Administrator's Cause or
Contribute Finding
    1. The Administrator Reasonably Defined the ``Air Pollutant''
for the Cause or Contribute Analysis
    2. The Administrator's Cause or Contribute Analysis Was
Reasonable
VI. Statutory and Executive 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
    K. Congressional Review Act

I. Introduction

A. Overview

    Pursuant to CAA section 202(a), the Administrator finds that
greenhouse gases in the atmosphere may reasonably be anticipated both
to endanger public health and to endanger public welfare. Specifically,
the Administrator is defining the ``air pollution'' referred to in CAA
section 202(a) to be the mix of six long-lived and directly-emitted
greenhouse gases: carbon dioxide (CO2), methane
(CH4), nitrous oxide (N2O), hydrofluorocarbons
(HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride
(SF6). In this document, these six greenhouse gases are
referred to as ``well-mixed greenhouse gases'' in this document (with
more precise meanings of ``long lived'' and ``well mixed'' provided in
Section IV.A).
    The Administrator has determined that the body of scientific
evidence compellingly supports this finding. The major assessments by
the U.S. Global Climate Research Program (USGCRP), the
Intergovernmental Panel on Climate Change (IPCC), and the National
Research Council (NRC) serve as the primary scientific basis supporting
the Administrator's endangerment finding.\1\ The Administrator reached
her determination by considering both observed and projected effects of
greenhouse gases in the atmosphere, their effect on climate, and the
public health and welfare risks and impacts associated with such
climate change. The Administrator's assessment focused on public health
and public welfare impacts within the United States. She also examined
the evidence with respect to impacts in other world regions, and she
concluded that these impacts strengthen the case for endangerment to
public health and welfare because impacts in other world regions can in
turn adversely affect the United States.
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    \1\ Section III of these Findings discusses the science on which
these Findings are based. In addition, the Technical Support
Document (TSD) accompanying these Findings summarizes the major
assessments from the USGCRP, IPCC, and NRC.
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    The Administrator recognizes that human-induced climate change has
the potential to be far-reaching and multi-dimensional, and in light of
existing knowledge, that not all risks and potential impacts can be
quantified or characterized with uniform metrics. There is variety not
only in the nature and potential magnitude of risks and impacts, but
also in our ability to characterize, quantify and project such impacts
into the future. The Administrator is using her judgment, based on
existing science, to weigh the threat for each of the identifiable
risks, to weigh the potential benefits where relevant, and ultimately
to assess whether these risks and effects, when viewed in total,
endanger public health or welfare.
    The Administrator has considered how elevated concentrations of the
well-mixed greenhouse gases and associated climate change affect public
health by evaluating the risks associated with changes in air quality,
increases in temperatures, changes in extreme weather events, increases
in food- and water-borne pathogens, and changes in aeroallergens. The
evidence concerning adverse air quality impacts provides strong and
clear support for an endangerment finding. Increases in ambient ozone
are expected to occur over broad areas of the country, and they are
expected to increase serious adverse health effects in large population
areas that are and may continue to be in nonattainment. The evaluation
of the potential risks associated with increases in ozone in attainment
areas also supports such a finding.
    The impact on mortality and morbidity associated with increases in
average temperatures, which increase the likelihood of heat waves, also
provides support for a public health endangerment finding. There are
uncertainties over the net health impacts of a temperature increase due
to decreases in cold-related mortality, but some recent evidence
suggests that the net impact on mortality is more likely to be adverse,
in a context where heat is already the leading cause of weather-related
deaths in the United States.
    The evidence concerning how human-induced climate change may alter
extreme weather events also clearly supports a finding of endangerment,
given the serious adverse impacts that can result from such events and
the increase in risk, even if small, of the occurrence and intensity of
events such as hurricanes and floods. Additionally, public health is
expected to be

adversely affected by an increase in the severity of coastal storm
events due to rising sea levels.
    There is some evidence that elevated carbon dioxide concentrations
and climate changes can lead to changes in aeroallergens that could
increase the potential for allergenic illnesses. The evidence on
pathogen borne disease vectors provides directional support for an
endangerment finding. The Administrator acknowledges the many
uncertainties in these areas. Although these adverse effects provide
some support for an endangerment finding, the Administrator is not
placing primary weight on these factors.
    Finally, the Administrator places weight on the fact that certain
groups, including children, the elderly, and the poor, are most
vulnerable to these climate-related health effects.
    The Administrator has considered how elevated concentrations of the
well-mixed greenhouse gases and associated climate change affect public
welfare by evaluating numerous and far-ranging risks to food production
and agriculture, forestry, water resources, sea level rise and coastal
areas, energy, infrastructure, and settlements, and ecosystems and
wildlife. For each of these sectors, the evidence provides support for
a finding of endangerment to public welfare. The evidence concerning
adverse impacts in the areas of water resources and sea level rise and
coastal areas provides the clearest and strongest support for an
endangerment finding, both for current and future generations. Strong
support is also found in the evidence concerning infrastructure and
settlements, as well ecosystems and wildlife. Across the sectors, the
potential serious adverse impacts of extreme events, such as wildfires,
flooding, drought, and extreme weather conditions, provide strong
support for such a finding.
    Water resources across large areas of the country are at serious
risk from climate change, with effects on water supplies, water
quality, and adverse effects from extreme events such as floods and
droughts. Even areas of the country where an increase in water flow is
projected could face water resource problems from the supply and water
quality problems associated with temperature increases and
precipitation variability, as well as the increased risk of serious
adverse effects from extreme events, such as floods and drought. The
severity of risks and impacts is likely to increase over time with
accumulating greenhouse gas concentrations and associated temperature
increases and precipitation changes.
    Overall, the evidence on risk of adverse impacts for coastal areas
provides clear support for a finding that greenhouse gas air pollution
endangers the welfare of current and future generations. The most
serious potential adverse effects are the increased risk of storm surge
and flooding in coastal areas from sea level rise and more intense
storms. Observed sea level rise is already increasing the risk of storm
surge and flooding in some coastal areas. The conclusion in the
assessment literature that there is the potential for hurricanes to
become more intense (and even some evidence that Atlantic hurricanes
have already become more intense) reinforces the judgment that coastal
communities are now endangered by human-induced climate change, and may
face substantially greater risk in the future. Even if there is a low
probability of raising the destructive power of hurricanes, this threat
is enough to support a finding that coastal communities are endangered
by greenhouse gas air pollution. In addition, coastal areas face other
adverse impacts from sea level rise such as land loss due to
inundation, erosion, wetland submergence, and habitat loss. The
increased risk associated with these adverse impacts also endangers
public welfare, with an increasing risk of greater adverse impacts in
the future.
    Strong support for an endangerment finding is also found in the
evidence concerning energy, infrastructure, and settlements, as well
ecosystems and wildlife. While the impacts on net energy demand may be
viewed as generally neutral for purposes of making an endangerment
determination, climate change is expected to result in an increase in
electricity production, especially supply for peak demand. This may be
exacerbated by the potential for adverse impacts from climate change on
hydropower resources as well as the potential risk of serious adverse
effects on energy infrastructure from extreme events. Changes in
extreme weather events threaten energy, transportation, and water
resource infrastructure. Vulnerabilities of industry, infrastructure,
and settlements to climate change are generally greater in high-risk
locations, particularly coastal and riverine areas, and areas whose
economies are closely linked with climate-sensitive resources. Climate
change will likely interact with and possibly exacerbate ongoing
environmental change and environmental pressures in settlements,
particularly in Alaska where indigenous communities are facing major
environmental and cultural impacts on their historic lifestyles. 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 for range shifts and constraints
from development, habitat fragmentation, invasive species, and broken
ecological connections will likely alter ecosystem structure, function,
and services, leading to predominantly negative consequences for
biodiversity and the provision of ecosystem goods and services.
    There is a potential for a net benefit in the near term \2\ for
certain crops, but there is significant uncertainty about whether this
benefit will be achieved given the various potential adverse impacts of
climate change on crop yield, such as the increasing risk of extreme
weather events. Other aspects of this sector may be adversely affected
by climate change, including livestock management and irrigation
requirements, and there is a risk of adverse effect on a large segment
of the total crop market. For the near term, the concern over the
potential for adverse effects in certain parts of the agriculture
sector appears generally comparable to the potential for benefits for
certain crops. However, The body of evidence points towards increasing
risk of net adverse impacts on U.S. food production and agriculture
over time, with the potential for significant disruptions and crop
failure in the future.
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    \2\ The temporal scope of impacts is discussed in more detail in
Section III.C. The phrase ``near term'' as used in this document
generally refers to the current time period from and the next few
decades. The phrase ``long term'' generally refers to a time frame
extending beyond that to approximately the middle to the end of this
century.
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    For the near term, the Administrator finds the beneficial impact on
forest growth and productivity in certain parts of the country from
elevated carbon dioxide concentrations and temperature increases to
date is offset by the clear risk from the observed increases in
wildfires, combined with risks from the spread of destructive pests and
disease. For the longer term, the risk from adverse effects increases
over time, such that overall climate change presents serious adverse
risks for forest productivity. There is compelling reason to find that
the support for a positive endangerment finding increases as one
considers expected future conditions where temperatures continue to
rise.
    Looking across all of the sectors discussed above, the evidence
provides compelling support for finding that greenhouse gas air
pollution endangers the public welfare of both current and

future generations. The risk and the severity of adverse impacts on
public welfare are expected to increase over time.
    The Administrator also finds that emissions of well-mixed
greenhouse gases from the transportation sources covered under CAA
section 202(a) \3\ contribute to the total greenhouse gas air
pollution, and thus to the climate change problem, which is reasonably
anticipated to endanger public health and welfare. The Administrator is
defining the air pollutant that contributes to climate change as the
aggregate group of the well-mixed greenhouse gases. The definition of
air pollutant used by the Administrator is based on the similar
attributes of these substances. These attributes include the fact that
they are sufficiently long-lived to be well mixed globally in the
atmosphere, that they are directly emitted, and that they exert a
climate warming effect by trapping outgoing, infrared heat that would
otherwise escape to space, and that they are the focus of climate
change science and policy.
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    \3\ Section 202(a) source categories include passenger cars,
heavy-, medium and light-duty trucks, motorcycles, and buses.
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    In order to determine if emissions of the well-mixed greenhouse
gases from CAA section 202(a) source categories contribute to the air
pollution that endangers public health and welfare, the Administrator
compared the emissions from these CAA section 202(a) source categories
to total global and total U.S. greenhouse gas emissions, finding that
these source categories are responsible for about 4 percent of total
global well-mixed greenhouse gas emissions and just over 23 percent of
total U.S. well-mixed greenhouse gas emissions. The Administrator found
that these comparisons, independently and together, clearly establish
that these emissions contribute to greenhouse gas concentrations. For
example, the emissions of well-mixed greenhouse gases from CAA section
202(a) sources are larger in magnitude than the total well-mixed
greenhouse gas emissions from every other individual nation with the
exception of China, Russia, and India, and are the second largest
emitter within the United States behind the electricity generating
sector. As the Supreme Court noted, ``[j]udged by any standard, U.S.
motor-vehicle emissions make a meaningful contribution to greenhouse
gas concentrations and hence, * * * to global warming.'' Massachusetts
v. EPA, 549 U.S. 497, 525 (2007).
    The Administrator's findings are in response to the Supreme Court's
decision in Massachusetts v. EPA. That case involved a 1999 petition
submitted by the International Center for Technology Assessment and 18
other environmental and renewable energy industry organizations
requesting that EPA issue standards under CAA section 202(a) for the
emissions of carbon dioxide, methane, nitrous oxide, and
hydrofluorocarbons from new motor vehicles and engines. The
Administrator's findings are in response to this petition and are for
purposes of CAA section 202(a).

B. Background Information Helpful To Understand These Findings

    This section provides some basic information regarding greenhouse
gases and the CAA section 202(a) source categories, as well as the
ongoing joint-rulemaking on greenhouse gases by EPA and the Department
of Transportation. Additional technical and legal background, including
a summary of the Supreme Court's Massachusetts v. EPA decision, can be
found in the Proposed Endangerment and Contribution Findings (74 FR
18886, April 24, 2009).
1. Greenhouse Gases and Transportation Sources Under CAA Section 202(a)
    Greenhouse gases are naturally present in the atmosphere and are
also emitted by human activities. Greenhouse gases trap the Earth's
heat that would otherwise escape from the atmosphere, and thus form the
greenhouse effect that helps keep the Earth warm enough for life. Human
activities are intensifying the naturally-occurring greenhouse effect
by adding greenhouse gases to the atmosphere. The primary greenhouse
gases of concern that are directly emitted by human activities include
carbon dioxide, methane, nitrous oxide, hydrofluorocarbons,
perfluorocarbons, and sulfur hexafluoride. Other pollutants (such as
aerosols) and other human activities, such as land use changes that
alter the reflectivity of the Earth's surface, also cause climatic
warming and cooling effects. In these Findings, the term ``climate
change'' generally refers to the global warming effect plus other
associated changes (e.g., precipitation effects, sea level rise,
changes in the frequency and severity of extreme weather events) being
induced by human activities, including activities that emit greenhouse
gases. Natural causes also, contribute to climate change and climatic
changes have occurred throughout the Earth's history. The concern now,
however, is that the changes taking place in our atmosphere as a result
of the well-documented buildup of greenhouse gases due to human
activities are changing the climate at a pace and in a way that
threatens human health, society, and the natural environment. Further
detail on the state of climate change science can be found in Section
III of these Findings as well as the technical support document (TSD)
that accompanies this action (www.epa.gov/climatechange/
endangerment.html).
    The transportation sector is a major source of greenhouse gas
emissions both in the United States and in the rest of the world. The
transportation sources covered under CAA section 202(a)--the section of
the CAA under which these Findings occur--include passenger cars,
light- and heavy-duty trucks, buses, and motorcycles. These
transportation sources emit four key greenhouse gases: carbon dioxide,
methane, nitrous oxide, and hydrofluorocarbons. Together, these
transportation sources are responsible for 23 percent of total annual
U.S. greenhouse gas emissions, making this source the second largest in
the United States behind electricity generation.\4\
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    \4\ The units for greenhouse gas emissions in these findings are
provided in carbon dioxide equivalent units, where carbon dioxide is
the reference gas and every other greenhouse gas is converted to its
carbon dioxide equivalent by using the 100-year global warming
potential (as estimated by the Intergovernmental Panel on Climate
Change (IPCC). assigned to each gas. The reference gas used is
CO2, and therefore Global Warming Potential (GWP)-
weighted emissions are measured in teragrams of CO2
equivalent (Tg CO2 eq.). In accordance with UNFCCC
reporting procedures, the United States quantifies greenhouse gas
emissions using the 100-year time frame values for GWPs established
in the IPCC Second Assessment Report.
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    Further discussion of the emissions data supporting the
Administrator's cause or contribute finding can be found in Section V
of these Findings, and the detailed greenhouse gas emissions data for
section 202(a) source categories can be found in Appendix B of EPA's
TSD.
2. Joint EPA and Department of Transportation Proposed Greenhouse Gas
Rule
    On September 15, 2009, EPA and the Department of Transportation's
National Highway Safety Administration (NHTSA) proposed a National
Program that would dramatically reduce greenhouse gas emissions and
improve fuel economy for new cars and trucks sold in the United States.
The combined EPA and NHTSA standards that make up this proposed
National Program would apply to passenger cars, light-duty trucks, and
medium-duty passenger vehicles, covering model years 2012 through 2016.
They proposed to require these vehicles to meet an estimated combined
average

emissions level of 250 grams of carbon dioxide per mile, equivalent to
35.5 miles per gallon (MPG) if the automobile industry were to meet
this carbon dioxide level solely through fuel economy improvements.
Together, these proposed standards would cut carbon dioxide emissions
by an estimated 950 million metric tons and 1.8 billion barrels of oil
over the lifetime of the vehicles sold under the program (model years
2012-2016). The proposed rulemaking can be viewed at (74 FR 49454,
September 28, 2009).

C. Public Involvement

    In response to the Supreme Court's decision, EPA has been examining
the scientific and technical basis for the endangerment and cause or
contribute decisions under CAA section 202(a) since 2007. The science
informing the decision-making process has grown stronger since our work
began. EPA's approach to evaluating the science, including comments
submitted during the public comment period, is further discussed in
Section III.A of these Findings. Public review and comment has always
been a major component of EPA's process.
1. EPA's Initial Work on Endangerment
    As part of the Advance Notice of Proposed Rulemaking: Regulating
Greenhouse Gas Emissions under the Clean Air Act (73 FR 44353)
published in July 2008, EPA provided a thorough discussion of the
issues and options pertaining to endangerment and cause or contribute
findings under the CAA. The Agency also issued a TSD providing an
overview of all the major scientific assessments available at the time
and emission inventory data relevant to the contribution finding
(Docket ID No. EPA-HQ-OAR-2008-0318). The comment period for that
Advance Notice was 120 days, and it provided an opportunity for EPA to
hear from the public with regard to the issues involved in endangerment
and cause or contribute findings as well as the supporting science. EPA
received, reviewed and considered numerous comments at that time and
this public input was reflected in the Findings that the Administrator
proposed in April 2009. In addition, many comments were received on the
TSD released with the Advance Notice and reflected in revisions to the
TSD released in April 2009 to accompany the Administrator's proposal.
All public comments on the Advance Notice are contained in the public
docket for this action (Docket ID No. EPA-HQ-OAR-2008-0318) accessible
through www.regulations.gov.
2. Public Involvement Since the April 2009 Proposed Endangerment
Finding
    The Proposed Endangerment and Cause or Contribute Findings for
Greenhouse Gases (Proposed Findings) was published on April 24, 2009
(74 FR 18886). The Administrator's proposal was subject to a 60-day
public comment period, which ended June 23, 2009, and also included two
public hearings. Over 380,000 public comments were received on the
Administrator's proposed endangerment and cause or contribute findings,
including comments on the elements of the Administrator's April 2009
proposal, the legal issues pertaining to the Administrator's decisions,
and the underlying TSD containing the scientific and technical
information.
    A majority of the comments (approximately 370,000) were the result
of mass mail campaigns, which are defined as groups of comments that
are identical or very similar in form and content. Overall, about two-
thirds of the mass-mail comments received are supportive of the
Findings and generally encouraged the Administrator both to make a
positive endangerment determination and implement greenhouse gas
emission regulations. Of the mass mail campaigns in disagreement with
the Proposed Findings most either oppose the proposal on economic
grounds (e.g., due to concern for regulatory measures following an
endangerment finding) or take issue with the proposed finding that
atmospheric greenhouse gas concentrations endanger public health and
welfare. Please note that for mass mailer campaigns, a representative
copy of the comment is posted in the public docket for this Action
(Docket ID No. EPA-HQ-OAR-2009-0171) at www.regulations.gov.
    Approximately 11,000 other public comments were received. These
comments raised a variety of issues related to the scientific and
technical information EPA relied upon in making the Proposed Findings,
legal and procedural issues, the content of the Proposed Findings, and
the implications of the Proposed Findings.
    In light of the very large number of comments received and the
significant overlap between many comments, EPA has not responded to
each comment individually. Rather, EPA has summarized and provided
responses to each significant argument, assertion and question
contained within the totality of the comments. EPA's responses to some
of the most significant comments are provided in these Findings.
Responses to all significant issues raised by the comments are
contained in the 11 volumes of the Response to Comments document,
organized by subject area (found in docket EPA-HQ-OAR-2009-0171).
3. Issues Raised Regarding the Rulemaking Process
    EPA received numerous comments on process-related issues, including
comments urging the Administrator to delay issuing the final findings,
arguing that it was improper for the Administrator to sever the
endangerment and cause or contribute findings from the attendant
section 202(a) standards, arguing the final decision was preordained by
the President's May vehicle announcement, and questioning the adequacy
of the comment period. Summaries of key comments and EPA's responses
are discussed in this section. Additional and more detailed responses
can be found in the Response to Comments document, Volume 11. As noted
in the Response to Comments document, EPA also received comments
supporting the overall process.
a. It Is Reasonable for the Administrator To Issue the Endangerment and
Cause or Contribute Findings Now
    Though the Supreme Court did not establish a specific deadline for
EPA to act, more than two and a half years have passed since the remand
from the Supreme Court, and it has been 10 years since EPA received the
original petition requesting that EPA regulate greenhouse gas emissions
from new motor vehicles. EPA has a responsibility to respond to the
Supreme Court's decision and to fulfill its obligations under current
law, and there is good reason to act now given the urgency of the
threat of climate change and the compelling scientific evidence.
    Many commenters urge EPA to delay making final findings for a
variety of reasons. They note that the Supreme Court did not establish
a deadline for EPA to act on remand. Commenters also argue that the
Supreme Court's decision does not require that EPA make a final
endangerment finding, and thus that EPA has discretionary power and may
decline to issue an endangerment finding, not only if the science is
too uncertain, but also if EPA can provide ``some reasonable
explanation'' for exercising its discretion. These commenters interpret
the Supreme Court decision not as rejecting all policy reasons for
declining to undertake an endangerment finding, but rather as
dismissing solely the policy reasons EPA set forth in 2003. Some
commenters cite language in the

Supreme Court decision regarding EPA's discretion regarding ``the
manner, timing, content, and coordination of its regulations,'' and the
Court's declining to rule on ``whether policy concerns can inform
EPA\'\s actions in the event that it makes'' a CAA section 202(a)
finding to support their position.
    Commenters then suggest a variety of policy reasons that EPA can
and should make to support a decision not to undertake a finding of
endangerment under CAA section 202(a)(1). For example, they argue that
a finding of endangerment would trigger several other regulatory
programs--such as the Prevention of Significant Deterioration (PSD)
provisions--that would impose an unreasonable burden on the economy and
government, without providing a benefit to the environment. Some
commenters contend that EPA should defer issuing a final endangerment
finding while Congress considers legislation. Many commenters note the
ongoing international discussions regarding climate change and state
their belief that unilateral EPA action would interfere with those
negotiations. Others suggest deferring the EPA portion of the joint
U.S. Department of Transportation (DOT)/EPA rulemaking because they
argue that the new Corporate Average Fuel Economy (CAFE) standards will
effectively result in lower greenhouse gas emissions from new motor
vehicles, while avoiding the inevitable problems and concerns of
regulating greenhouse gases under the CAA.
    Other commenters argue that the endangerment determination has to
be made on the basis of scientific considerations only. These
commenters state that the Court was clear that ``[t]he statutory
question is whether sufficient information exists to make an
endangerment finding,'' and thus, only if ``the scientific uncertainty
is so profound that it precludes EPA from making a reasoned judgment as
to whether greenhouse gases contribute to global warming,'' may EPA
avoid making a positive or negative endangerment finding. Many
commenters urge EPA to take action quickly. They note that it has been
10 years since the original petition requesting that EPA regulate
greenhouse gas emissions from motor vehicles was submitted to EPA. They
argue that climate change is a serious problem that requires immediate
action.
    EPA agrees with the commenters who argue that the Supreme Court
decision held that EPA is limited to consideration of science when
undertaking an endangerment finding, and that we cannot delay issuing a
finding due to policy concerns if the science is sufficiently certain
(as it is here). The Supreme Court stated that ``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'' 549 U.S. at 533. Some commenters point to
this last provision, arguing that the policy reasons they provide are a
``reasonable explanation'' for not moving forward at this time.
However, this ignores other language in the decision that clearly
indicates that the Court interprets the statute to allow for the
consideration only of science. For example, in rejecting the policy
concerns expressed by EPA in its 2003 denial of the rulemaking
petition, the Court noted that ``it is evident [the policy
considerations] have nothing to do with whether greenhouse gas
emissions contribute to climate change. Still less do they amount to a
reasoned justification for declining to form a scientific judgment''
Id. at 533-34 (emphasis added).
    Moreover, the Court also held that ``[t]he statutory question is
whether sufficient information exists to make an endangerment finding''
Id. at 534. Taken as a whole, the Supreme Court's decision clearly
indicates that policy reasons do not justify the Administrator avoiding
taking further action on the question here.
    We also note that the language many commenters quoted from the
Supreme Court decision about EPA's discretion regarding the manner,
timing and content of Agency actions, and the ability to consider
policy concerns, relate to the motor vehicle standards required in the
event that EPA makes a positive endangerment finding, and not the
finding itself. EPA has long taken the position that it does have such
discretion in the standard-setting step under CAA section 202(a).
b. The Administrator Reasonably Proceeded With the Endangerment and
Cause or Contribute Findings Separate From the CAA Section 202(a)
Standard Rulemaking
    As discussed in the Proposed Findings, typically endangerment and
cause or contribute findings have been proposed concurrently with
proposed standards under various sections of the CAA, including CAA
section 202(a). EPA received numerous comments on its decision to
propose the endangerment and cause or contribute findings separate from
any standards under CAA section 202(a).
    Commenters argue that EPA has no authority to issue an endangerment
determination under CAA section 202(a) separate and apart from the
rulemaking to establish emissions standards under CAA section 202(a).
According to these commenters, CAA section 202(a) provides only one
reason to issue an endangerment determination, and that is as the basis
for promulgating emissions standards for new motor vehicles; thus, it
does not authorize such a stand-alone endangerment finding, and EPA may
not create its own procedural rules completely divorced from the
statutory text. They continue by stating that while CAA section 202(a)
says EPA may issue emissions standards conditioned on such a finding,
it does not say EPA may first issue an endangerment determination and
then issue emissions standards. In addition, they contend, the
endangerment proposal and the emissions standards proposal need to be
issued together so commenters can fully understand the implications of
the endangerment determination. Failure to do so, they argue, deprives
the commenters of the opportunity to assess the regulations that will
presumably follow from an endangerment finding. They also argue that
the expected overlap between reductions in emissions of greenhouse
gases from CAA section 202(a) standards issued by EPA and CAFE
standards issued by DOT calls into question the basis for the CAA
section 202(a) standards and the related endangerment finding, and that
EPA is improperly motivated by an attempt to trigger a cascade of
regulations under the CAA and/or to promote legislation by Congress.
    EPA disagrees with the commenters' claims and arguments. The text
of CAA section 202(a) is silent on this issue. It does not specify the
timing of an endangerment finding, other than to be clear that
emissions standards may not be issued unless such a determination has
been made. EPA is exercising the procedural discretion that is provided
by CAA section 202(a)'s lack of specific direction. The text of CAA
section 202(a) envisions two separate actions by the Administrator: (1)
A determination on whether emissions from classes or categories of new
motor vehicles cause or contribute to air pollution that may reasonably
be anticipated to endanger, and (2) a separate decision on issuance of
appropriate emissions standards for such classes or categories. The
procedure followed in this rulemaking, and the companion rulemaking
involving emissions standards for light duty motor vehicles, is
consistent with CAA section 202(a). EPA will issue final emissions
standards for new motor

vehicles only if affirmative findings are made concerning contribution
and endangerment, and such emissions standards will not be finalized
prior to making any such determinations. While it would also be
consistent with CAA section 202(a) to issue the greenhouse gas
endangerment and contribution findings and emissions standards for new
light-duty vehicles in the same rulemaking, e.g., a single proposal
covering them and a single final rule covering them, nothing in CAA
section 202(a) requires such a procedural approach, and nothing in the
approach taken in this case violates the text of CAA section 202(a).
Since Congress was silent on this issue, and more than one procedural
approach may accomplish the requirements of CAA section 202(a), EPA has
the discretion to use the approach considered appropriate in this case.
Once the final affirmative contribution and endangerment findings are
made, EPA has the authority to issue the final emissions standards for
new light-duty motor vehicles; however, as the Supreme Court has noted,
the agency has `significant latitude as to the manner, timing, [and]
content * * * of its regulations . * * *' Massachusetts v. EPA, 549
U.S. at 533. That includes the discretion to issue them in a separate
rulemaking.
    Commenters' argument would also lead to the conclusion that EPA
could not make an endangerment finding for the entire category of new
motor vehicles, as it is doing here, unless EPA also conducted a
rulemaking that set emissions standards for all the classes and
categories of new motor vehicles at the same time. This narrow
procedural limitation would improperly remove discretion that CAA
section 202(a) provides to EPA.
    EPA has the discretion under CAA section 202(a) to consider classes
or categories of new motor vehicles separately or together in making a
contribution and endangerment determination. This discretion would be
removed under commenters' interpretation, by limiting this to only
those cases in which EPA was also ready to issue emissions standards
for all of the classes or categories covered by the endangerment
finding. However, nothing in the text of CAA section 202(a) places such
a limit on EPA's discretion in determining how to group classes or
categories of new motor vehicles for purposes of the contribution and
endangerment findings. This limitation would not be appropriate,
because the issues of contribution and endangerment are separate and
distinct from the issues of setting emissions standards. EPA, in this
case, is fully prepared to go forward with the contribution and
endangerment determination, while it is not ready to proceed with
rulemaking for each and every category of new motor vehicles in the
first rulemaking to set emissions standards. Section 202(a) of the CAA
provides EPA discretion with regard to when and how it conducts its
rulemakings to make contribution and endangerment findings, and to set
emissions standards, and the text of CAA section 202(a) does not
support commenters attempt to limit such discretion.
    Concerns have been raised that the failure to issue the proposed
endangerment finding and the proposed emissions standard together
preclude commenters from assessing and considering the implications of
the endangerment finding and the regulations that would likely flow
from such a finding. However, commenters have failed to explain how
this interferes in any way with their ability to comment on the
endangerment finding. In fact it does not interfere, because the two
proposals address separate and distinct issues. The endangerment
finding concerns the contribution of new motor vehicles to air
pollution and the effect of that air pollution on public health or
welfare. The emissions standards, which have been proposed (74 FR
49454, September 28, 2009), concern the appropriate regulatory
emissions standards if affirmative findings are made on contribution
and endangerment. These two proposals address different issues. While
commenters have the opportunity to comment on the proposed emissions
standards in that rulemaking, they have not shown, and cannot show,
that they need to have the emissions standards proposal before them in
order to provide relevant comments on the proposed contribution or
endangerment findings. Further discussion of this issue can be found in
Section II of these Findings, and discussion of the timing of this
action and its relationship to other CAA provisions and Congressional
action can be found in Section III of these Findings and Volume 11 of
the Response to Comments document.
c. The Administrator's Final Decision Was Not Preordained by the
President's May Vehicle Announcement
    EPA received numerous comments arguing that the President's
announcement of a new ``National Fuel Efficiency Policy'' on May 19,
2009 seriously undermines EPA's ability to provide objective
consideration of and a legally adequate response to comments objecting
to the previously proposed endangerment findings.
    Commenters' conclusion is based on the view that the President's
announced policy requires EPA to promulgate greenhouse gas emissions
standards under CAA section 202(a), that the President's and
Administrator Jackson's announcement indicated that the endangerment
rulemaking was but a formality and that a final endangerment finding
was a fait accompli. Commenters argue that this means the result of
this rulemaking has been preordained and the merits of the issues have
been prejudged.
    EPA disagrees. Commenters' arguments wholly exaggerate and
mischaracterize the circumstances. In the April 24, 2009 endangerment
proposal EPA was clear that the two steps in the endangerment provision
have to be satisfied in order for EPA to issue emissions standards for
new motor vehicles under CAA section 202(a) (74 FR at 18888, April 24,
2009). This was repeated when EPA issued the Notice of Upcoming Joint
Rulemaking to Establish Vehicle GHG Emissions and CAFE Standards (74 FR
24007 May 22, 2009) (Notice of Intent or NOI). This was repeated again
when EPA issued proposed greenhouse gas emissions standards for certain
new motor vehicles (74 FR 49454, September 28, 2009). EPA has
consistently made it clear that issuance of new motor vehicle standards
requires and is contingent upon satisfaction of the two-part
endangerment test.
    On May 19, 2009 EPA issued the joint Notice of Intent, which
indicated EPA's intention to propose new motor vehicle standards. All
of the major motor vehicle manufacturers, their trade associations, the
State of California, and several environmental organizations announced
their full support for the upcoming rulemaking. Not surprisingly, on
the same day the President also announced his full support for this
action. Commenters, however, erroneously equate this Presidential
support with a Presidential directive that requires EPA to prejudge and
preordain the result of this rulemaking.
    The only evidence they point to are simply indications of
Presidential support. Commenters point to a press release, which
unsurprisingly refers to the Agency's announcement as delivering on the
President's commitment to enact more stringent fuel economy standards,
by bringing ``all stakeholders to the table and [coming] up with a
plan'' for solving a serious problem. The plan that was announced, of
course, was a plan to conduct notice and comment

rulemaking. The press release itself states that President Obama ``set
in motion a new national policy,'' with the policy ``aimed'' at
reducing greenhouse gas emissions for new cars and trucks. What was
``set in motion'' was a notice and comment rulemaking described in the
NOI issued by EPA on the same day. Neither the President nor EPA
announced a final rule or a final direction that day, but instead did
no more than announce a plan to go forward with a notice and comment
rulemaking. That is how the plan ``delivers on the President's
commitment'' to enact more stringent standards. The announcement was
that a notice and comment rulemaking would be initiated with the aim of
adopting certain emissions standards.
    That is no different from what EPA or any other agency states when
it issues a notice of proposed rulemaking. It starts a process that has
the aim of issuing final regulations if they are deemed appropriate at
the end of the public process. The fact that an Agency proposes a
certain result, and expects that a final rule will be the result of
setting such a process in motion, is the ordinary course of affairs in
notice and comment rulemakings. This does not translate into prejudging
the final result or having a preordained result that de facto negates
the public comment process. The President's press release of May 19,
2009 was a recognition that this notice and comment rulemaking process
would be set in motion, as well as providing his full support for the
Agency to go forward in this direction; it was no more than that.
    The various stakeholders who announced their support for the plan
that had been set in motion all recognized that full notice and comment
rulemaking was part of the plan, and they all reserved their rights to
participate in such notice and comment rulemaking. For example, see the
letter of support from Ford Motor Company, which states that ``Ford
fully supports proposal and adoption of such a National Program, which
we understand will be subject to full notice-and-comment rulemaking,
affording all interested parties including Ford the right to
participate fully, comment, and submit information, the results of
which are not pre-determined but depend upon processes set by law.''
d. The Notice and Comment Period Was Adequate
    Many commenters argue that the 60-day comment period was
inadequate. Commenters claim that a 60-day period was insufficient time
to fully evaluate the science and other information that informed the
Administrator's proposal. Some commenters assert that because the
comment period for the Proposed Finding substantially overlapped with
the comment period for the Mandatory Greenhouse Gas Reporting Rule, as
well as Congress' consideration of climate legislation, their ability
to fully participate in the notice and comment period was ``seriously
compromised.'' Moreover, they continue, because EPA had not yet
proposed CAA section 202(a) standards, there was no valid reason to
fail to extend the comment period. Several commenters and other
entities had also requested that EPA extend the comment period.
    Some commenters assert that the notice provided by this rulemaking
was ``defective'' because the Federal Register notice announcing the
proposal had an error in the e-mail address for the docket. At least
one commenter suggests that this error deprives potential commenters of
their Due Process under the Fifth Amendment of the Constitution, citing
Armstrong v. Manzo, 380 U.S. 545, 552 (1965), and that failure to
``correct'' the minor typographical error in the e-mail address and
extend the comment period would make the rule ``subject to reversal''
in violation of the CAA, Administrative Procedure Act (APA), the Due
Process clause of the Constitution, and EO 12866.
    Finally, for many of the same reasons that commenters argue a 60-
day comment period was inadequate, several commenters request that EPA
reopen and/or extend the comment period. One commenter requests that
the comment period be reopened because there was new information
regarding data used by EPA in the Proposed Findings. In particular, the
commenter alleges that it recently became aware that one of the sources
of global climate data had destroyed the raw data for its data set of
global surface temperatures. The commenter argues that this alleged
destruction of raw data violates scientific standards, calls into
question EPA's reliance on that data in these Findings, and
necessitates a reopening of the proceedings. Other commenters request
that the comment period be extended and/or reopened due to the release
of a Federal government document on the impact of climate change in the
United States near the end of the comment period, as well as the
release of an internal EPA staff document discussing the science.
    The official public comment period on the proposed rule was
adequate. First, a 60-day comment period satisfies the procedural
requirements of CAA section 307 of the CAA, which requires a 30-day
comment period, and that the docket be kept open to receive rebuttal or
supplemental information as follow-up to any hearings for 30 days
following the hearings. EPA met those obligations here--the comment
period opened on April 24, 2009, the last hearing was on May 21, 2009
and the comment period closed June 23, 2009.
    Second, as explained in letters denying requests to extend the
comment period, a very large part of the information and analyses for
the Proposed Findings had been previously released in July 30, 2008, as
part of the Advance Notice of Proposed Rulemaking: Regulating
Greenhouse Gas Emissions under the Clean Air Act (ANPR) (73 FR 44353).
The public comment period for the ANPR is discussed above in Section
I.C.1 of these Findings. The Administrator explained that the comment
period for that ANPR was 120 days and that the major recent scientific
assessments that EPA relied upon in the TSD released with the ANPR had
previously each gone through their own public review processes and have
been publicly available for some time. In other words, EPA has provided
ample time for review, particularly with regard to the technical
support for the Findings. See, for example, EPA Letter to Congressman
Issa dated June 17, 2009, a copy of which is available at http://
epa.gov/climatechange/endangerment.html.
    Moreover, the comment period was not rendered insufficient merely
because other climate-related proceedings were occurring
simultaneously.
    While one commenter suggests that the convergence of several
different climate-related activities has ``seriously compromised''
their ability to participate in the comment process, that commenter was
able to submit an 89 page comment on this proposal alone. Moreover, it
is hardly rare that more than one rule is out for comment at the same
time. As noted above, EPA has received a substantial number of
significant comments on the Proposed Findings, and has thoroughly
considered and responded to significant comments.
    EPA finds no evidence that a typographical error in the docket e-
mail address of the Federal Register notice announcing the proposal
prevented the public from having a meaningful opportunity to comment,
and therefore deprived them of due process. Although the minor error--
which involved a word processing auto-correction that turned a short
dash into a long dash--appeared in the FR version of the Proposed
Findings, the e-mail address is correct

in the signature version of the Proposed Findings posted on EPA's Web
site until publication in the Federal Register, and in the
``Instructions for Submitting Written Comments'' document on the Web
site for the rulemaking. EPA has received over 190,000 e-mails to the
docket e-mail address to date, so the minor typographical error
appearing in only one location has not been an impediment to interested
parties' e-mailing comments. Moreover, EPA provided many other avenues
for interested parties to submit comments in addition to the docket e-
mail address, including via www.regulations.gov, mail, and fax; each of
these options have been utilized by many commenters. EPA is confident
that the minor typographical error did not prevent anyone from
submitting written comments, by e-mail or otherwise, and that the
public was provided ``meaningful participation in the regulatory
process'' as mentioned in EO 12866.
    Our response regarding the request to reopen the comment period due
to concerns about alleged destruction of raw global surface data is
discussed more fully in the Response to Comments document, Volume 11.
The commenter did not provide any compelling reason to conclude that
the absence of these data would materially affect the trends in the
temperature records or conclusions drawn about them in the assessment
literature and reflected in the TSD. The Hadley Centre/Climate Research
Unit (CRU) temperature record (referred to as HadCRUT) is just one of
three global surface temperature records that EPA and the assessment
literature refer to and cite. National Oceanic and Atmospheric
Administration (NOAA) and National Aeronautics and Space Administration
(NASA) also produce temperature records, and all three temperature
records have been extensively peer reviewed. Analyses of the three
global temperature records produce essentially the same long-term
trends as noted in the Climate Change Science Program (CCSP) (2006)
report ``Temperature Trends in the Lower Atmosphere,'' IPCC (2007), and
NOAA's study \5\ ``State of the Climate in 2008''. Furthermore, the
commenter did not demonstrate that the allegedly destroyed data would
materially alter the HadCRUT record or meaningfully hinder its
replication. The raw data, a small part of which has not been public
(for reasons described at: https://www.uea.ac.uk/mac/comm/media/press/
2009/nov/CRUupdate), are available in a quality-controlled (or
homogenized, value-added) format and the methodology for developing the
quality-controlled data is described in the peer reviewed literature
(as documented at http://www.cru.uea.ac.uk/cru/data/temperature/).
---------------------------------------------------------------------------

    \5\ Peterson, T.C., and M.O. Baringer (Eds.) (2009) State of the
Climate in 2008. Bull. Amer. Meteor. Soc., 90, S1-S196.
---------------------------------------------------------------------------

    The release of the U.S. Global Climate Research Program (USGCRP)
report on impacts of climate change in the United States in June 2009
also did not necessitate extending the comment period. This report was
issued by the USGCRP, formerly the Climate Change Science Program
(CCSP), and synthesized information contained in prior CCSP reports and
other synthesis reports, many of which had already been published (and
were included in the TSD for the Proposed Findings). Further, the
USGCRP report itself underwent notice and comment before it was
finalized and released.
    Regarding the internal EPA staff paper that came to light during
the comment period, several commenters submitted a copy of the EPA
staff paper with their comments; EPA's response to the issues raised by
the staff paper are discussed in the Response to Comments document,
Volume 1. The fact that some internal agency deliberations were made
public during the comment period does not in and of itself call into
question those deliberations. As our responses to comments explain, EPA
considered the concerns noted in the staff paper during the proposal
stage, as well as when finalizing the Findings. There was nothing about
those internal comments that required an extension or reopening of the
comment period.
    Thus, the opportunity for comment fully satisfies the CAA and
Constitutional requirement of Due Process. Cases cited by commenters do
not indicate otherwise. The comment period and thorough response to
comment documents in the docket indicate that EPA has given people an
opportunity to be heard in a ``meaningful time and a meaningful
matter.'' Armstrong v. Manzo, 380 U.S. 545, 552 (1965). Interested
parties had full notice of the rulemaking proceedings and a significant
opportunity to participate through the comment process and multiple
hearings.
    For all the above reasons, EPA's denial of the requests for
extension or reopening of the comment period was entirely reasonable in
light of the extensive opportunity for public comment and heavy amount
of public participation during the comment period. EPA has fully
complied with all applicable public participation requirements for this
rulemaking.
e. These Findings Did Not Necessitate a Formal Rulemaking Under the
Administrative Procedure Act
    One commenter, with the support of others, requests that EPA
undertake a formal rulemaking process for the Findings, on the record,
in accordance with the procedures described in sections 556-557 of the
Administrative Procedure Act (APA). The commenter requests a multi-step
process, involving additional public notice, an on-the-record
proceeding (e.g., formal administrative hearing) with the right of
appeal, utilization of the Clean Air Scientific Advisory Committee
(CASAC) and its advisory proceedings, and designation of
representatives from other executive branch agencies to participate in
the formal proceeding and any CASAC advisory proceeding.
    The commenter asserts that while EPA is not obligated under the CAA
to undertake these additional procedures, the Agency nonetheless has
the legal authority to engage in such a proceeding. The commenter
believes this proceeding would show that EPA is ``truly committed to
scientific integrity and transparency.'' The commenter cites several
cases to argue that refusal to proceed on the record would be
``arbitrary and capricious'' or would be an ``abuse of discretion.''
The allegation at the core of the commenter's argument is that profound
and wide-ranging scientific uncertainties exist in the Proposed
Findings and in the impacts on health and welfare discussed in the TSD.
To support this argument, the commenter provides lengthy criticisms of
the science. The commenter also argues that the regulatory cascade that
would be ``unleashed'' by a positive endangerment finding warrants the
more formal proceedings.
    Finally, the commenter suggests that EPA engage in ``formal
rulemaking'' procedures in part due to the Administrative Conference of
the United States' (ACUS) recommended factors for engaging in formal
rulemaking. The commenter argues that the current action is
``complex,'' ``open-ended,'' and the costs that errors in the action
may pose are ``significant.''
    EPA is denying the request to undertake an ``on the record'' formal
rulemaking. EPA is under no obligation to follow the extraordinarily
rarely used formal rulemaking provisions of the APA. First, CAA section
307(d) of the CAA clearly states that the rulemaking provisions of CAA
section 307(d), not APA sections 553 through 557, apply to certain
specified actions, such as this

one. EPA has satisfied all the requirements of CAA section 307(d).
Indeed, the commenter itself ``is not asserting that the Clean Air Act
expressly requires'' the additional procedures it requests. Moreover,
the commenter does not discuss how the suggested formal proceeding
would fit into the informal rulemaking requirements of CAA section
307(d) that do apply.
    Formal rulemaking is very rarely used by Federal agencies. The
formal rulemaking provisions of the APA are only triggered when the
statute explicitly calls for proceedings ``on the record after
opportunity for an agency hearing.'' United States v. Florida East
Coast Ry. Co., 410 U.S. 224, 241 (1973). The mere mention of the word
``hearing'' does not trigger the formal rulemaking provisions of the
APA. Id. The CAA does not include the statutory phrase required to
trigger the formal rulemaking provisions of the APA (and as noted above
the APA does not apply in the first place). Congress specified that
certain rulemakings under the CAA follow the rulemaking procedures
outlined in CAA section 307(d) rather than the APA ``formal
rulemaking'' commenter suggests.
    Despite the inapplicability of the formal rulemaking provisions to
this action, commenters suggest that to refuse to voluntarily undertake
rulemaking provisions not preferred by Congress would make EPA's
rulemaking action an ``abuse of discretion.'' EPA disagrees with this
claim, and cases cited by the commenter do not indicate otherwise. To
support the idea that an agency decision to engage in informal
rulemaking could be an abuse of discretion, commenter cites Ford Motor
Co. v. FTC, 673 F.2d 1008 (9th Cir. 1981). In Ford Motor Co., the court
ruled that the FTC's decision regarding an automobile dealership should
have been resolved through a rulemaking rather than an individualized
adjudication. Id. at 1010. In that instance, the court favored
``rulemaking'' over adjudication--not ``formal rulemaking'' over the
far more common ``informal rulemaking.'' The case stands only for the
non-controversial proposition that sometimes agency use of
adjudications may rise to an abuse of discretion where a rulemaking
would be more appropriate--whether formal or informal. The Commenter
does not cite a single judicial opinion stating that an agency abused
its discretion by following the time-tested and Congressionally-favored
informal rulemaking provisions of the CAA or the APA instead of the
rarely used formal APA rulemaking provisions.
    The commenter also alludes to the possibility that the choice of
informal rulemaking may be ``arbitrary and capricious. EPA disagrees
that the choice to follow the frequently used, and CAA required,
informal rulemaking procedures is arbitrary and capricious. The
commenter cites Vermont Yankee Nuclear Power Corp. v. NRDC, 435 U.S.
519 (1978) for the proposition that ``extremely compelling
circumstances'' could lead to a court overturning agency action for
declining to follow extraneous procedures. As the commenter notes, in
Vermont Yankee the Supreme Court overturned a lower court decision for
imposing additional requirements not required by applicable statutes.
Even if the dicta in Vermont Yankee could be applied contrary to the
holding of the case in the way the commenter suggests, EPA's decision
to follow frequently used informal rulemaking procedures for this
action is highly reasonable.
    As for the ACUS factors the commenter cites in support of its
request, as the commenter notes, the ACUS factors are mere
recommendations. While EPA certainly respects the views of ACUS, the
recommendations are not binding on the Agency. In addition, EPA has
engaged in a thorough, traditional rulemaking process that ensures that
any concerns expressed by the commenter have been addressed. EPA has
fully satisfied all applicable law in their consideration of this
rulemaking.
    Finally, as explained in Section III of these Findings and the
Response to Comments document, EPA's approach to evaluating the
evidence before it was entirely reasonable, and did not require a
formal hearing. EPA relied primarily on robust synthesis reports that
have undergone peer review and comment. The Agency also carefully
considered the comments received on the Proposed Findings and TSD,
including review of attached studies and documents. The public has had
ample opportunity to provide its views on the science, and the record
supporting these final findings indicates that EPA carefully considered
and responded to significant public comments. To the extent the
commenter's concern is that a formal proceeding will help ensure the
right action in response to climate change is taken, that is not an
issue for these Findings. As discussed in Section III of these
Findings, this science-based judgment is not the forum for considering
the potential mitigation options or their impact.

II. Legal Framework for This Action

    As discussed in the Proposed Findings, two statutory provisions of
the CAA govern the Administrator's Findings. Section 202(a) of the CAA
sets forth a two-part test for regulatory action under that provision:
Endangerment and cause or contribute. Section 302 of the CAA contains
definitions of the terms ``air pollutant'' and ``effects on welfare''.
Below is a brief discussion of these statutory provisions and how they
govern the Administrator's decision, as well as a summary of
significant legal comments and EPA's responses to them.

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

1. The Statutory Framework
    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.
    Based on the text of CAA section 202(a) and its legislative
history, the Administrator interprets the two-part test as follows.
Further discussion of this two-part test can be found in Section II of
the preamble for the Proposed Findings. First, the Administrator is
required to protect public health and welfare, but she is not asked to
wait until harm has occurred. EPA must be ready to take regulatory
action to prevent harm before it occurs. Section 202(a)(1) requires the
Administrator to ``anticipate'' ``danger'' to public health or welfare.
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 of great concern, but the likelihood low, while on the
other end the severity may be less, 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.
    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 inquiries. Third, as discussed
further below, 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, including catastrophic scenarios and their probabilities
as well as the less severe effects. As explained below, vulnerable
subpopulations face serious health risks as a result of climate change.
    In addition, 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 CAA 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). 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 in
determining whether, under the circumstances presented, the cause or
contribute criterion has been met. 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--and thus
contributing to--the problem.
    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 (DC 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.).
    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 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. As discussed in the Proposed Findings, this
interpretation is based on and supported by the language in CAA section
202(a), its legislative history and case law.
2. Summary of Response to Key Legal Comments on the Interpretation of
the CAA Section 202(a) Endangerment and Cause or Contribute Test
    EPA received numerous comments regarding the interpretation of CAA
section 202(a) set forth in the Proposed Findings. Below is a brief
discussion of some of the key adverse legal comments and EPA's
responses. Other key legal comments and EPA's responses are provided in
later sections discussing the Administrator's findings.
    Additional and more detailed summaries and responses can be found
in the Response to Comments document. As noted in the Response to
Comments document, EPA also received comments supporting its legal
interpretations.
a. The Administrator Properly Interpreted the Precautionary and
Preventive Nature of the Statutory Language
    Various commenters argue either that the endangerment test under
CAA section 202(a) is not precautionary and preventive in nature, or
that EPA's interpretation and application is so extreme that it is
contrary to what Congress intended in 1977, and effectively guarantees
an affirmative endangerment finding. Commenters also argue that the
endangerment test improperly shifts the burdens to the opponents of an
endangerment finding and is tantamount to assuming the air pollution is
harmful unless it is shown to be safe.
    EPA rejects the argument that the endangerment test in CAA section
202(a) is not precautionary or preventive in nature. As discussed in
more detail in the proposal, Congress relied heavily on the en banc
decision in Ethyl when it revised section 202(a) and other CAA
provisions to adopt the current language on endangerment and
contribution. 74 FR 18886, 18891-2. The Ethyl court could not have been
clearer on the precautionary nature of a criteria based on
endangerment. The court rejected the argument that EPA had to find
actual harm was occurring before it could make the required
endangerment finding. The court stated that:

    The Precautionary Nature of ``Will Endanger.'' Simply as a
matter of plain meaning, we have difficulty crediting petitioners'
reading of the ``will endanger'' standard. The meaning of
``endanger'' is not disputed. Case law and dictionary definition
agree that endanger means something less than actual harm. When one
is endangered, harm is threatened; no actual injury need ever occur.
Thus, for example, a town may be ``endangered'' by a threatening
plague or hurricane and yet emerge from the danger completely
unscathed. A statute allowing for regulation in the face of danger
is, necessarily, a precautionary statute. Regulatory action may be
taken before the threatened harm occurs; indeed, the very existence
of such precautionary legislation would seem to demand that
regulatory action precede, and, optimally, prevent, the perceived
threat. As should be apparent, the ``will endanger'' language of
Section 211(c)(1)(A) makes it such a precautionary statute. Ethyl at
13 (footnotes omitted).

    Similarly, the court stated that ``[i]n sum, based on the plain
meaning of the statute, the juxtaposition of CAA section 211 with CAA
sections 108 and 202, and the Reserve Mining precedent, we conclude
that the ``will endanger'' standard is precautionary in nature and does
not require proof of actual harm before regulation is appropriate.''
Ethyl at 17. It is this authority to act before harm has occurred that
makes it a preventive, precautionary provision.
    It is important to note that this statement was in the context of
rejecting an argument that EPA had to prove actual harm before it could
adopt fuel control regulations under then CAA section 211(c)(1). The
court likewise rejected the argument that EPA had to show that such
harm was ``probable.''

The court made it clear that determining endangerment entails judgments
involving both the risk or likelihood of harm and the severity of the
harm if it were to occur. Nowhere did the court indicate that the
burden was on the opponents of an endangerment finding to show that
there was no endangerment. The opinion focuses on describing the burden
the statute places on EPA, rejecting Ethyl's arguments of a burden to
show actual or probable harm.
    Congress intentionally adopted a precautionary and preventive
approach. It stated that the purpose of the 1977 amendments was to
``emphasize the preventive or precautionary nature of the act, i.e., to
assure that regulatory action can effectively prevent harm before it
occurs; to emphasize the predominate value of protection to public
health.'' \6\ Congress also stated that it authorized the Administrator
to weigh risks and make projections of future trends, a ``middle road
between those who would impose a nearly impossible standard of proof on
the Administrator before he may move to protect public health and those
who would shift the burden of proof for all pollutants to make the
pollutant source prove the safety of its emissions as a condition of
operation.'' Leg. His. at 2516.
---------------------------------------------------------------------------

    \6\ The Supreme Court recognized that the current language in
section 202(a), adopted in 1977, is ``more protective'' than the
1970 version that was similar to the section 211 language before the
DC Circuit in Ethyl. Massachusetts v. EPA, 549 U.S. at 506, fn 7.
---------------------------------------------------------------------------

    Thus, EPA rejects commenters' arguments. Congress intended this
provision to be preventive and precautionary in nature, however it did
not shift the burden of proof to opponents of an endangerment finding
to show safety or no endangerment. Moreover, as is demonstrated in the
following, EPA has not shifted the burden of proof in the final
endangerment finding, but rather is weighing the likelihood and
severity of harms to arrive at the final finding. EPA has not applied
an exaggerated or dramatically expanded precautionary principle, and
instead has exercised judgment by weighing and balancing the factors
that are relevant under this provision.
b. The Administrator Does Not Need To Find That the Control Measures
Following an Endangerment Finding Would Prevent at Least a Substantial
Part of the Danger in Order To Find Endangerment
    Several commenters argue that it is unlawful for EPA to make an
affirmative endangerment finding unless EPA finds that the regulatory
control measures contemplated to follow such a finding would prevent at
least a substantial part of the danger from the global climate change
at which the regulation is aimed. This hurdle is also described by
commenters as the regulation ``achieving the statutory objective of
preventing damage'', or ``fruitfully attacking'' the environmental and
public health danger at hand by meaningfully and substantially reducing
it. Commenters point to Ethyl Corp. v. EPA, 541 F.2d 1 (DC Cir. 1976)
(en banc) as support for this view, as well as portions of the
legislative history of this provision.
    Commenters contend that EPA has failed to show that this required
degree of meaningful reduction of endangerment would be achieved
through regulation of new motor vehicles based on an endangerment
finding. In making any such showing, commenters argue that EPA would
need to account for the following: (1) The fact that any regulation
would be limited to new motor vehicles, if not the subset of new motor
vehicles discussed in the President's May 2009 announcement, (2) any
increase in emissions from purchasers delaying purchases of new
vehicles subject to any greenhouse gas emissions standards, or
increasing the miles traveled of new vehicles with greater fuel
economy, (3) the fact that only a limited portion of the new motor
vehicle emissions of greenhouse gases would be controlled, (4) the fact
that CAFE standards would effectively achieve the same reductions, and
(5) the fact that any vehicle standards would not themselves reduce
global temperatures. Some commenters refer to EPA's proposal for
greenhouse gas emissions standards for new motor vehicles as support
for these arguments, claiming the proposed new motor vehicle emission
standards are largely duplicative of the standards proposed by the
National Highway Traffic Safety Administration (NHTSA), and the
estimates of the impacts of the proposed standards confirm that EPA's
proposed standards cannot ``fruitfully attack'' global climate change
(74 FR 49454, September 28, 2009).
    Commenters attempt to read into the statute a requirement that is
not there. EPA interprets the endangerment provision of CAA section
202(a) as not requiring any such finding or showing as described by
commenters. The text of CAA section 202(a) does not support such an
interpretation. The endangerment provision calls for EPA, in its
judgment, to determine whether air pollution is reasonably anticipated
to endanger public health or welfare, and whether emissions from
certain sources cause or contribute to such air pollution. If EPA makes
an affirmative finding, then it shall set emissions standards
applicable to emissions of such air pollutants from new motor vehicles.
There is no reference in the text of the endangerment or cause or
contribute provision to anything concerning the degree of reductions
that would be achieved by the emissions standards that would follow
such a finding. The Administrator's judgment is directed at the issues
of endangerment and cause or contribute, not at how effective the
resulting emissions control standards will be.
    As in the several other similar provisions adopted in the 1977
amendments, in CAA section 202(a) Congress explicitly separated two
different decisions to be made, providing different criteria for them.
The first decision involves the air pollution and the endangerment
criteria, and the contribution to the air pollution by the sources. The
second decision involves how to regulate the sources to control the
emissions if an affirmative endangerment and contribution finding are
made. In all of the various provisions, there is broad similarity in
the phrasing of the endangerment and contribution decision. However,
for the decision on how to regulate, there are a wide variety of
different approaches adopted by Congress. In some case, EPA has
discretion whether to issue standards or not, while in other cases, as
in CAA section 202(a), EPA is required to issue standards. In some
cases, the regulatory criteria are general, as in CAA section 202(a);
in others, they provide significantly more direction as to how
standards are to be set, as in CAA section 213(a)(4).
    As the Supreme Court made clear in Massachusetts v. EPA, EPA's
judgment in making the endangerment and contribution findings is
constrained by the statute, and EPA is to decide these issues based
solely on the scientific and other evidence relevant to that decision.
EPA may not ``rest[] on reasoning divorced from the statutory text,''
and instead EPA's exercise of judgment must relate to whether an air
pollutant causes or contributes to air pollution that endangers.
Massachusetts v. EPA, 549 U.S. at 532. As the Supreme Court noted, EPA
must ``exercise discretion within defined statutory limits.'' Id. at
533. EPA's belief one way or the other regarding whether regulation of
greenhouse gases from new motor vehicles would be ``effective'' is
irrelevant in making the endangerment and contribution decisions before
EPA. Id. Instead ``[t]he statutory question is

whether sufficient information exists to make an endangerment finding''
Id. at 534.
    The effectiveness of a potential future control strategy is not
relevant to deciding whether air pollution levels in the atmosphere
endanger. It is also not relevant to deciding whether emissions of
greenhouse gases from new motor vehicles contribute to such air
pollution. Commenters argue that Congress implicitly imposed a third
requirement, that the future control strategy have a certain degree of
effectiveness in reducing the endangerment before EPA could make the
affirmative findings that would authorize such regulation. There is no
statutory text that supports such an interpretation, and the Supreme
Court makes it clear that EPA has no discretion to read this kind of
additional factor into CAA section 202(a)'s endangerment and
contribution criteria. In fact, the Supreme Court rejected similar
arguments that EPA had the discretion to consider various other factors
besides endangerment and contribution in deciding whether to deny a
petition. Massachusetts v. EPA, 549 U.S. at 532-35.
    Commenters point to language from the Ethyl case to support their
position, noting that the DC Circuit referred to the emissions control
regulation adopted by EPA under CAA section 211(c) as one that would
``fruitfully attack'' the environmental and public health danger by
meaningfully and substantially reducing the danger. It is important to
understand the context for this discussion in Ethyl. The petitioner
Ethyl Corp. argued that EPA had to show that the health threat from the
emissions of lead from the fuel additive being regulated had to be
considered in isolation, and the threat ``in and of itself'' from the
additive had to meet the test of endangerment in CAA section 211(c).
EPA had rejected this approach, and had interpreted CAA section
211(c)(1) as calling for EPA to look at the cumulative impact of lead,
and to consider the impact of lead from emissions related to use of the
fuel additive in the context all other human exposure to lead. The
court rejected Ethyl's approach and supported EPA's interpretation. The
DC Circuit noted that Congress was fully aware that the burden of lead
on the body was caused by multiple sources and that it would be of no
value to try and determine the effect on human health from the lead
automobile emissions by themselves. The court specifically noted that
``the incremental effect of lead emissions on the total body lead
burden is of no practical value in determining whether health is
endangered,'' but recognized that this incremental effect is of value
``in deciding whether the lead exposure problem can fruitfully be
attacked through control of lead additives.'' Ethyl, 541 F.2d at 31 fn
62. The court made clear that the factor that was critically important
to determining the effectiveness of the resulting control strategy--the
incremental effect of automobile lead emissions on total body burden--
was irrelevant and of no value in determining whether the endangerment
criteria was met. Thus it is clear that the court in Ethyl did not
interpret then CAA section 211(c)(1)(A) as requiring EPA to make a
showing of the effectiveness of the resulting emissions control
strategy, and instead found just the opposite, that the factors that
would determine effectiveness are irrelevant to determining
endangerment.
    Commenters also cite to the legislative history, noting that
Congress referred to the ``preventive or precautionary nature of the
Act, i.e., to assure that regulatory action can effectively prevent
harm before it occurs.'' Leg. Hist. at 2516. However, this statement by
Congress is presented as an answer to the question on page 2515,
``Should the Administrator act to prevent harm before it occurs or
should he be authorized to regulate an air pollutant only if he finds
actual harm has already occurred.'' Leg. Hist. at 2515. In this
context, the discussion on page 2516 clearly indicates that there is no
opportunity for prevention or precaution if the test is one of actual
harm already occurring. This discussion does not say or imply that even
if the harm has not occurred, you can not act unless you also show that
your action will effectively address it. This discussion concerns the
endangerment test, not the criteria for standard setting. The criteria
for standard setting address how the agency should act to address the
harm, and as the Ethyl case notes, the factors relevant to how to
``fruitfully attack'' the harm are irrelevant to determining whether
the harm is one that endangers the public health or welfare.
    As with current CAA section 202(a), there is no basis to conflate
these two separate decisions and to read into the endangerment criteria
an obligation that EPA show that the resulting emissions control
strategy or strategies will have some significant degree of harm
reduction or effectiveness in addressing the endangerment. The
conflating of the two decisions is not supported in the text of this
provision, by the Supreme Court in Massachusetts v. EPA, by the DC
Circuit in Ethyl, or by Congress in the legislative history of this
provision. It would be an unworkable interpretation, calling for EPA to
project out the result of perhaps not one, but even several, future
rulemakings stretching over perhaps a decade or decades. Especially in
the context of global climate change, the effectiveness of a control
strategy for new motor vehicles would have to be viewed in the context
of a number of future motor vehicle regulations, as well as in the
larger context of the CAA and perhaps even global context. That would
be an unworkable and speculative requirement to impose on EPA as a
precondition to answering the public health and welfare issues before
it, as they are separate and apart from the issues involved with
developing, implementing and evaluating the effectiveness of emissions
control strategies.
c. The Administrator Does Not Need To Find There Is Significant Risk of
Harm
    Commenters argue that Congress established a minimum requirement
that there be a ``significant risk of harm'' to find endangerment. They
contend that this requirement stemmed from the Ethyl case, and that
Congress adopted this view. According to the commenters, the risk is
the function of two variables: the nature of the hazard at issue and
the likelihood of its occurrence. Commenters argue that Congress
imposed a requirement that this balance demonstrate a ``significant
risk of harm'' to strike a balance between the precautionary nature of
the CAA and the burdensome economic and societal consequences of
regulation.
    There are two basic problems with the commenters' arguments. First,
commenters equate ``significant risk of harm'' as the overall test for
endangerment, however the Ethyl case and the legislative history treat
the risk of harm as only one of the two components that are to be
considered in determining endangerment.--, The two components are the
likelihood or risk of a harm occurring, and the severity of harm if it
were to occur. Second, commenters equate it to a minimum statutory
requirement. However, while the court in the Ethyl case made it clear
that the facts in that case met the then applicable endangerment
criteria, it also clearly said it was not determining what other facts
or circumstances might amount to endangerment, including cases where
the likelihood of a harm occurring was less than a significant risk of
the harm.
    In the EPA rulemaking that led to the Ethyl case, EPA stated that
the requirement to reduce lead in gasoline ``is based on the finding
that lead

particle emissions from motor vehicles present a significant risk of
harm to the health of urban populations, particularly to the health of
city children'' (38 FR 33734, December 6, 1973). The court in Ethyl
supported EPA's determination, and addressed a variety of issues.
First, it determined that the ``will endanger'' criteria of then CAA
section 211(c) was intended to be precautionary in nature. It rejected
arguments that EPA had to show proof of actual harm, or probable harm.
Ethyl, 541 F.2d at 13-20. It was in this context, evaluating
petitioner's arguments on whether the likelihood of a harm occurring
had to rise to the level of actual or probable harm, that the court
approved of EPA's view that a significant risk of harm could satisfy
the statutory criteria. The precautionary nature of the provision meant
that EPA did not need to show that either harm was actually occurring
or was probable.
    Instead, the court made it clear that the concept of endangerment
is ``composed of reciprocal elements of risk and harm,'' Ethyl at 18.
This means ``the public health may properly be found endangered both by
a lesser risk of a greater harm and by a greater risk of lesser harm.
Danger depends upon the relation between the risk and harm presented by
each case, and cannot legitimately be pegged to `probable' harm,
regardless of whether that harm be great or small.'' The Ethyl court
pointed to the decision by the 8th Circuit in Reserve Mining Co. v.
EPA, 514 F.2d 492 (8th Cir, 1975), which interpreted similar language
under the Federal Water Pollution Control Act, where the 8th Circuit
upheld an endangerment finding in a case involving ``reasonable medical
concern,'' or a ``potential'' showing of harm. This was further
evidence that a minimum ``probable'' likelihood of harm was not
required.
    The Ethyl court made it clear that there was no specific magnitude
of risk of harm occurring that was required. ``Reserve Mining
convincingly demonstrates that the magnitude of risk sufficient to
justify regulation is inversely proportional to the harm to be
avoided.'' Ethyl at 19. This means there is no minimum requirement that
the magnitude of risk be ``significant'' or another specific level of
likelihood of occurrence. You need to evaluate the risk of harm in the
context of the severity of the harm if it were to occur. In the case
before it, the Ethyl court noted that ``the harm caused by lead
poisoning is severe.'' Even with harm as severe as lead poisoning, EPA
did not rely on ``potential'' risk or a ``reasonable medical concern.''
Instead, EPA found that there was a significant risk of this harm to
health. This finding of a significant risk was less than the level of
``probable'' harm called for by the petitioner Ethyl Corporation but
was ``considerably more certain than the risk that justified regulation
in Reserve Mining of a comparably `fright-laden' harm.'' Ethyl at 19-
20. The Ethyl court concluded that this combination of risk (likelihood
of harm) and severity of harm was sufficient under CAA section 211(c).
``Thus we conclude that however far the parameters of risk and harm
inherent in the `will endanger' standard might reach in an appropriate
case, they certainly present a `danger' that can be regulated when the
harm to be avoided is widespread lead poisoning and the risk of that
occurrence is `significant'.'' Ethyl at 20.
    Thus, the court made it clear that the endangerment criteria was
intended to be precautionary in nature, that the risk of harm was one
of the elements to consider in determining endangerment, and that the
risk of harm needed to be considered in the context of the severity of
the potential harm. It also concluded that a significant risk of harm
coupled with an appropriate severity of the potential harm would
satisfy the statutory criteria, and in the case before it the
Administrator was clearly authorized to determine endangerment where
there was a significant risk of harm that was coupled with a severe
harm such as lead poisoning.
    Importantly, the court also made it clear that it was not
determining a minimum threshold that always had to be met. Instead, it
emphasized that the risk of harm and severity of the potential harm had
to be evaluated on a case by case basis. The court specifically said it
was not determining ``however far the parameters of risk and harm * * *
might reach in an appropriate case.'' Ethyl at 20. Also see Ethyl fn 17
at 13. The court recognized that this balancing of risk and harm ``must
be confined to reasonable limits'' and even absolute certainty of a de
minimis harm might not justify government action. However, ``whether a
particular combination of slight risk and great harm, or great risk and
slight harm constitutes a danger must depend on the facts of each
case.'' Ethyl at fn 32 at 18.\7\
---------------------------------------------------------------------------

    \7\ Commenters point to Amer. Farm Bureau Ass'n v. EPA, 559 F.3d
512, 533 (DC Cir. 2009) as supporting their argument. However, in
that case the Court made clear that EPA's action was not subject to
the endangerment criterion in CAA section 108 but instead was
subject to CAA section 109's requirement that the primary NAAQS be
requisite to protect the public health with an adequate margin of
safety. Under that provision and its case law, the Court upheld
EPA's reasoned balancing of the uncertainty regarding the link
between non-urban thoracic coarse PM and adverse health effects, the
large population groups potentially exposed to these particles, and
the nature and degree of the health effects at issue. Citing to
EPA's reasoning at 71 FR 61193 in the final PM rule, the court
explained that EPA need not wait for conclusive proof of harm before
setting a NAAQS under section 109 for this kind of coarse PM. The
Court's reference to EPA's belief that there may be a significant
risk to public health is not stated as any sort of statutory
minimum, but instead refers to the Agency's reasoning at 71 FR
61193, which displays a reasoned balancing of possibility of harm
and severity of harm if it were to occur.
---------------------------------------------------------------------------

    In some cases, commenters confuse matters by switching the
terminology, and instead refer to effects that ``significantly harm''
the public health or welfare. As with the reference to ``significant
risk of harm,'' commenters fail to recognize that there are two
different aspects that must be considered, risk of harm and severity of
harm, and neither of these aspects has a requirement that there be a
finding of ``significance.'' The DC Circuit in Ethyl makes clear that
it is the combination of these two aspects that must be evaluated for
purposes of endangerment, and there is no requirement of
``significance'' assigned to either of the two aspects that must
instead be evaluated in combination. Congress addressed concerns over
burdensome economic and societal consequences in the various statutory
provisions that provide the criteria for standard setting or other
agency action if there is an affirmative endangerment finding. Those
statutory provisions, for example, make standard setting discretionary
or specify how cost and other factors are to be taken into
consideration in setting standards. However, the issues of risk of harm
and severity of harm if it were to occur are separate from the issues
of the economic impacts of any resulting regulatory provisions (see
below).
    As is clear in the prior summary of the endangerment findings and
the more detailed discussion later, the breadth of the sectors of our
society that are affected by climate change and the time frames at
issue mean there is a very wide range of risks and harms that need to
be considered, from evidence of various harms occurring now to evidence
of risks of future harms. The Administrator has determined that the
body of scientific evidence compellingly supports her endangerment
finding.

B. Air Pollutant, Public Health and Welfare

    The CAA defines both ``air pollutant'' and ``effects on welfare.''
We provide both definitions here again for convenience.
    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). As the Supreme Court
held, 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.
    ``Regarding `effects on 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).
    As noted in the Proposed Findings, 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.
    Although the CAA defines ``effects on welfare'' as discussed above,
there are no definitions of ``public health'' or ``public welfare'' in
the CAA. The Supreme Court has discussed the concept of public health
in the context of whether costs of implementation can be considered
when setting the health based primary 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. In the past, when considering public
health, EPA has looked at morbidity, such as 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).
    EPA received numerous comments regarding its proposed
interpretations of air pollutant and public health and welfare.
Summaries of key comments and EPA's responses are discussed in Sections
IV and V of these Findings. Additional and more detailed summaries and
responses can be found in the Response to Comments document. As noted
in the Response to Comments document, EPA also received comments
supporting its legal interpretations.

III. EPA's Approach for Evaluating the Evidence Before It

    This section discusses EPA's approach to evaluating the evidence
before it, including the approach taken to the scientific evidence, the
legal framework for this decision making, and several issues critical
to determining the scope of the evaluation performed.

A. The Science on Which the Decisions Are Based

    In 2007, EPA initiated its assessment of the science and other
technical information to use in addressing the endangerment and cause
or contribute issues before it under CAA section 202(a). This
scientific and technical information was developed in the form of a TSD
in 2007. An earlier draft of this document was released as part of the
ANPR published July 30, 2008 (73 FR 44353). That earlier draft of the
TSD relied heavily on the IPCC Fourth Assessment Report of 2007, key
NRC reports, and a limited number of then-available synthesis and
assessment products of the U.S. Climate Change Science Program (CCSP;
now encompassed by USGCRP). EPA received a number of comments
specifically focused on the TSD during the 120-day public comment
period for the ANPR.
    EPA revised and updated the TSD in preparing the Proposed Findings
on endangerment and cause or contribute. Many of the comments received
on the ANPR were reflected in the draft TSD released in April 2009 that
served as the underlying scientific and technical basis for the
Administrator's Proposed Findings, published April 24, 2009 (74 FR
18886). The draft TSD released in April 2009 also reflected the
findings of 11 new synthesis and assessment products under the U.S.
CCSP that had been published since July 2008.
    The TSD that summarizes scientific findings from the major
assessments of the USGCRP, the IPCC, and the NRC accompanies these
Findings. The TSD is available at www.epa.gov/climatechange/
endangerment.html and in the docket for this action. It also includes
the most recent comprehensive assessment of the USGCRP, Global Climate
Change Impacts in the United States,\8\ published in June 2009. In
addition, the TSD incorporates up-to-date observational data for a
number of key climate variables from the NOAA, and the most up-to-date
emissions data from EPA's annual Inventory of U.S. Greenhouse Gas
Emissions and Sinks, published in April, 2009.\9\ And finally, as
discussed in Section I.B of these Findings, EPA received a large number
of public comments on the Administrator's Proposed Findings, many of
which addressed science issues either generally or specifically as
reflected in the draft TSD released with the April 2009 proposal. A
number of edits and updates were made to the draft TSD as a result of
these comments.\10\
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    \8\ Karl, T., J. Melillo, and T. Peterson (Eds.) (2009) Global
Climate Change Impacts in the United States. Cambridge University
Press, Cambridge, United Kingdom.
    \9\ U.S. EPA (2009) Inventory of U.S. Greenhouse Gas Emissions
and Sinks: 1990-2007. EPA-430-R-09-004, Washington, DC.
    \10\ EPA has placed within the docket a separate memo ``Summary
of Major Changes to the Technical Support Document'' identifying
where within the TSD such changes were made relative to the draft
TSD released in April 2009.
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    EPA is giving careful consideration to all of the scientific and
technical information in the record, as discussed below. However, the
Administrator is relying on the major assessments of the USGCRP, IPCC,
and NRC as the primary scientific and technical basis of her
endangerment decision for a number of reasons.
    First, these assessments address the scientific issues that the
Administrator must examine for the endangerment analysis. When viewed
in total, these assessments address the issue of greenhouse gas
endangerment by providing data and information on: (1) The amount of
greenhouse gases being emitted by human activities; (2) how greenhouse
gases have been and continue to accumulate in the atmosphere as a
result of human activities; (3) changes to the Earth's energy balance
as a result of the buildup of atmospheric greenhouse gases; (4)
observed temperature and other climatic changes at the global and
regional scales; (5) observed changes in other climate-sensitive
sectors and systems of the human and natural environment; (6) the
extent to which observed climate change and other changes in climate-
sensitive systems can be attributed to the human-induced buildup of
atmospheric greenhouse gases; (7) future projected climate change under
a range of different scenarios of changing greenhouse gas emission
rates; and (8) the projected risks and impacts to

human health, society and the environment.
    Second, as indicated above, these assessments are recent and
represent the current state of knowledge on the key elements for the
endangerment analysis. It is worth noting that the June 2009 assessment
of the USGCRP incorporates a number of key findings from the 2007 IPCC
Fourth Assessment Report; such findings include the attribution of
observed climate change to human emissions of greenhouse gases, and the
future projected scenarios of climate change for the global and
regional scales. This demonstrates that much of the underlying science
that EPA has been utilizing since 2007 has not only been in the public
domain for some time, but also has remained relevant and robust.
    Third, these assessments are comprehensive in their coverage of the
greenhouse gas and climate change problem, and address the different
stages of the emissions-to-potential-harm chain necessary for the
endangerment analysis. In so doing, they evaluate the findings of
numerous individual peer-reviewed studies in order to draw more general
and overarching conclusions about the state of science. The USGCRP,
IPCC, and NRC assessments synthesize literally thousands of individual
studies and convey the consensus conclusions on what the body of
scientific literature tells us.
    Fourth, these assessment reports undergo a rigorous and exacting
standard of peer review by the expert community, as well as rigorous
levels of U.S. government review and acceptance. Individual studies
that appear in scientific journals, even if peer reviewed, do not go
through as many review stages, nor are they reviewed and commented on
by as many scientists. The review processes of the IPCC, USGCRP, and
NRC (explained in fuller detail in the TSD and the Response to Comments
document, Volume 1) provide EPA with strong assurance that this
material has been well vetted by both the climate change research
community and by the U.S. government. These assessments therefore
essentially represent the U.S. government's view of the state of
knowledge on greenhouse gases and climate change. For example, with
regard to government acceptance and approval of IPCC assessment
reports, the USGCRP Web site states that: ``When governments accept the
IPCC reports and approve their Summary for Policymakers, they
acknowledge the legitimacy of their scientific content.'' \11\ It is
the Administrator's view that such review and acceptance by the U.S.
Government lends further support for placing primary weight on these
major assessments.
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    \11\ http://www.globalchange.gov/publications/reports/ipcc-
reports.
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    It is EPA's view that the scientific assessments of the IPCC,
USGRCP, and the NRC represent the best reference materials for
determining the general state of knowledge on the scientific and
technical issues before the agency in making an endangerment decision.
No other source of information provides such a comprehensive and in-
depth analysis across such a large body of scientific studies, adheres
to such a high and exacting standard of peer review, and synthesizes
the resulting consensus view of a large body of scientific experts
across the world. For these reasons, the Administrator is placing
primary and significant weight on these assessment reports in making
her decision on endangerment.
    A number of commenters called upon EPA to perform a new and
independent assessment of all of the underlying climate change science,
separate and apart from USGCRP, IPCC, and NRC. In effect, commenters
suggest that EPA is either required to or should ignore the attributes
discussed above concerning these assessment reports, and should instead
perform its own assessment of all of the underlying studies and
information.
    In addition to the significant reasons discussed above for relying
on and placing primary weight on these assessment reports, EPA has been
a very active part of the U.S. government climate change research
enterprise, and has taken an active part in the review, writing, and
approval of these assessments. EPA was the lead agency for three
significant reports under the USGCRP \12\, and recently completed an
assessment addressing the climate change impacts on U.S. air quality--a
report on which the TSD heavily relies for that particular issue. EPA
was also involved in review of the IPCC Fourth Assessment Report, and
in particular took part in the approval of the summary for policymakers
for the Working Group II Volume, Impacts, Adaptation and
Vulnerability.\13\ The USGCRP, IPCC, and NRC assessments have been
reviewed and formally accepted by, commissioned by, or in some cases
authored by, U.S. government agencies and individual government
scientists. These reports already reflect significant input from EPA's
scientists and the scientists of many other government agencies.
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    \12\ CCSP (2009) Coastal Sensitivity to Sea-Level Rise: A Focus
on the Mid-Atlantic Region. A Report by the U.S. Climate Change
Science Program and the Subcommittee on Global Change Research.
[James G. Titus (Coordinating Lead Author), K. Eric Anderson, Donald
R. Cahoon, Dean B. Gesch, Stephen K. Gill, Benjamin T. Gutierrez, E.
Robert Thieler, and S. Jeffress Williams (Lead Authors)], U.S.
Environmental Protection Agency, Washington DC, USA, 320 pp. CCSP
(2008) Preliminary review of adaptation options for climate-
sensitive ecosystems and resources. A Report by the U.S. Climate
Change Science Program and the Subcommittee on Global Change
Research. [Julius, S.H., J.M. West (eds.), J.S. Baron, B. Griffith,
L.A. Joyce, P. Kareiva, B.D. Keller, M.A. Palmer, C.H. Peterson, and
J.M. Scott (Authors)]. U.S. Environmental Protection Agency,
Washington, DC, USA, 873 pp. CCSP (2008) Analyses of the effects of
global change on human health and welfare and human systems. A
Report by the U.S. Climate Change Science Program and the
Subcommittee on Global Change Research. [Gamble, J.L. (ed.), K.L.
Ebi, F.G. Sussman, T.J. Wilbanks, (Authors)]. U.S. Environmental
Protection Agency, Washington, DC, USA.
    \13\ IPCC (2007) Climate Change 2007: Impacts, Adaptation and
Vulnerability. Contribution of Working Group II to the Fourth
Assessment Report of the Intergovernmental Panel on Climate Change,
M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and
C.E. Hanson, Eds., Cambridge University Press, Cambridge, UK, 976pp.
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    EPA has no reason to believe that the assessment reports do not
represent the best source material to determine the state of science
and the consensus view of the world's scientific experts on the issues
central to making an endangerment decision with respect to greenhouse
gases. EPA also has no reason to believe that putting this significant
body of work aside and attempting to develop a new and separate
assessment would provide any better basis for making the endangerment
decision, especially because any such new assessment by EPA would still
have to give proper weight to these same consensus assessment reports.
    In summary, EPA concludes that its reliance on existing and recent
synthesis and assessment reports is entirely reasonable and allows EPA
to rely on the best available science.\14\ EPA also recognizes that
scientific research is very active in many areas addressed in the TSD
(e.g., aerosol effects on climate, climate feedbacks such as water
vapor, and internal and external climate forcing mechanisms), as well
as for some emerging issues (e.g., ocean acidification and climate
change effects on water quality). EPA recognizes the potential
importance of new scientific research, and the value of an ongoing
process to take more recent science into account. EPA reviewed new
literature in

preparation of this TSD to evaluate its consistency with recent
scientific assessments. We also considered public comments received and
studies incorporated by reference. In a number of cases, the TSD was
updated based on such information to add context for assessment
literature findings, which includes supporting information and/or
qualifying statements. In other cases, material that was not
incorporated into the TSD is discussed within the Response to Comments
document.
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    \14\ It maintains the highest level of adherence to Agency and
OMB guidelines for data and scientific integrity and transparency.
This is discussed in greater detail in EPA's Response to Comments
document.
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    EPA reviewed these individual studies that were not considered or
reflected in these major assessments to evaluate how they inform our
understanding of how greenhouse gas emissions affect climate change,
and how climate change may affect public health and welfare. Given the
very large body of studies reviewed and assessed in developing the
assessment reports, and the rigor and breadth of that review and
assessment, EPA placed limited weight on the much smaller number of
individual studies that were not considered or reflected in the major
assessments. EPA reviewed them largely to see if they would lead EPA to
change or place less weight on the judgments reflected in the
assessment report. While EPA recognizes that some studies are more
useful or informative than others, and gave each study it reviewed the
weight it was due, the overall conclusion EPA drew from its review of
studies submitted by commenters was that the studies did not change the
various conclusions or judgments EPA would draw based on the assessment
reports.
    Many comments focus on the scientific and technical data underlying
the Proposed Findings, such as climate change science and greenhouse
gas emissions data. These comments cover a range of topics and are
summarized and responded to in the Response to Public Comments
document. The responses note those cases where a technical or
scientific comment resulted in an editorial or substantive change to
the TSD. The final TSD reflects all changes made as a result of public
comments.

B. The Law on Which the Decisions Are Based

    In addition to grounding these determinations on the science, they
are also firmly grounded in EPA's legal authority. Section II of these
Findings provides an in-depth discussion of the legal framework for the
endangerment and cause or contribute decisions under CAA section
202(a), with additional discussion in Section II of the Proposed
Finding (74 FR 18886, 18890, April 24, 2009). A variety of important
legal issues are also discussed in Sections III, IV, and V of these
Findings, as well as in the Response to Comments document, Volume 11.
Section IV and V of these Findings explain the Administrator's
decisions, and how she exercised her judgment in making the
endangerment and contribution determinations, based on the entire
scientific record before her and the legal framework structuring her
decision making.

C. Adaptation and Mitigation

    Following the language of CAA section 202(a), in which the
Administrator, in her judgment, must determine if greenhouse gases
constitute the air pollution that may be reasonably anticipated to
endanger public health or welfare, EPA evaluated, based primarily on
the scientific reports discussed above, how greenhouse gases and other
climate-relevant substances are affecting the atmosphere and climate,
and how these climate changes affect public health and welfare, now and
in the future. Consistent with EPA's scientific approach underlying the
Administrator's Proposed Findings, EPA did not undertake a separate
analysis to evaluate potential societal and policy responses to any
threat (i.e., the endangerment) that may exist due to anthropogenic
emissions of greenhouse gases. Risk reduction through adaptation and
greenhouse gas mitigation measures is of course a strong focal area of
scientists and policy makers, including EPA; however, EPA considers
adaptation and mitigation to be potential responses to endangerment,
and as such has determined that they are outside the scope of the
endangerment analysis.
    The Administrator's position is not that adaptation will not occur
or cannot help protect public health and welfare from certain impacts