 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued April 8, 2005                      Decided July 15, 2005
                                    Reissued September 13, 2005

                         No. 03-1361

       COMMONWEALTH OF MASSACHUSETTS, ET AL.,
                  PETITIONERS

                               v.

           ENVIRONMENTAL PROTECTION AGENCY,
                     RESPONDENT

    ALLIANCE OF AUTOMOBILE MANUFACTURERS, ET AL.,
                    INTERVENORS


                 Consolidated with Nos.
  03-1362, 03-1363, 03-1364, 03-1365, 03-1366, 03-1367,
                        03-1368


          On Petitions for Review of an Order of the
             Environmental Protection Agency


     James R. Milkey and Howard Fox argued the cause for
petitioners. With them on the briefs were Thomas F. Reilly,
Attorney General, Attorney General’s Office of the
Commonwealth of Massachusetts, William L. Pardee, Assistant
Attorney General, Joseph Mendelson, III, David Bookbinder,
Bill Lockyer, Attorney General, Attorney General’s Office of the
                               2

State of California, Nicholas Stern and Marc N. Melnick, Deputy
Attorneys General, David Doniger, Richard Blumenthal,
Attorney General, Attorney General’s Office of the State of
Connecticut, Kimberly Massicotte and Matthew Levine,
Assistant Attorneys General, Peter C. Harvey, Attorney General,
Attorney General’s Office of the State of New Jersey, Stefanie
A. Brand, Deputy Attorney General, Hardy Myers, Attorney
General, Attorney General’s Office of the State of Oregon,
Philip Schradle, Special Counsel, Lisa Madigan, Attorney
General, Attorney General’s Office of the State of Illinois, Gary
Feinerman, Solicitor General, Gerald T. Karr and Thomas E.
Davis, Assistant Attorneys General, Patricia A. Madrid,
Attorney General, Attorney General’s Office of the State of New
Mexico, Stuart M. Bluestone, Deputy Attorney General, Patrick
C. Lynch, Attorney General, Attorney General’s Office of the
State of Rhode Island, Tricia K. Jedele, Special Assistant, G.
Steven Rowe, Attorney General, Attorney General’s Office of
the State of Maine, Gerald D. Reid, Assistant Attorney General,
Eliot Spitzer, Attorney General, Attorney General’s Office of the
State of New York, Peter Lehner and J. Jared Snyder, Assistant
Attorneys General, William H. Sorrell, Attorney General,
Attorney General’s Office of the State of Vermont, Erick Titrud
and Kevin O. Leske, Assistant Attorneys General, Rob
McKenna, Attorney General, Attorney General’s Office of the
State of Washington, David K. Mears, Assistant Attorney
General, John Hogrogian, Assistant Corporation Counsel,
Corporation Counsel of the City of New York, Julie M.
Anderson, Fiti A. Sunia, Attorney General, Attorney General’s
Office of the American Samoa, Ralph S. Tyler, III, Solicitor,
City of Baltimore, William Phelan, Jr., Counsel, James B. Tripp,
Robert J. Spagnoletti, Attorney General, Attorney General’s
Office of the District of Columbia, Edward E. Schwab, Deputy
Attorney General, and Donna M. Murasky, Senior Litigation
Counsel.
                              3

     Rebecca L. Bernard and Jeremy Kyle Kinner were on the
brief of amici curiae Indigenous Environmental Network,
REDOIL and Physicians for Social Responsibility.

    Jeffrey Bossert Clark, Deputy Assistant Attorney General,
U.S. Department of Justice, argued the cause for respondent.
With him on the brief were Thomas L. Sansonetti, Assistant
Attorney General, Jon M. Lipshultz, Attorney, Ann R. Klee,
General Counsel, U.S. Environmental Protection Agency, and
John T. Hannon and Nancy Ketcham-Colwill, Counsel.

     Neil D. Gordon, Assistant Attorney General, Attorney
General’s Office of the State of Michigan, argued the cause for
intervenors States of Michigan, et al., and amicus curiae State
of Indiana. With him on the briefs were Alan F. Hoffman,
Assistant Attorney General, Jane E. Atwood, Assistant Attorney
General, Attorney General’s Office of the State of Texas,
Douglas Conde, Deputy Attorney General, Attorney General’s
Office of the State of Idaho, Charles M. Carvell, Assistant
Attorney General, Attorney General’s Office of the State of
North Dakota, Fred Nelson, Assistant Attorney General,
Attorney General’s Office of the State of Utah, Roxanne Giedd,
Deputy Attorney General, Attorney General’s Office of the State
of South Dakota, Steven E. Mulder, Assistant Attorney General,
Attorney General’s Office of the State of Alaska, David W.
Davies, Attorney, Attorney General’s Office of the State of
Kansas, David D. Cookson and Natalee J. Hart, Assistant
Attorneys General, Attorney General’s Office of the State of
Nebraska, Dale T. Vitale, Senior Deputy Attorney General,
Attorney General’s Office of the State of Ohio, and Thomas M.
Fisher, Special Counsel, Attorney General’s Office of the State
of Indiana.

   Norman W. Fichthorn, Allison D. Wood, William A.
Anderson, II., Eric P. Gotting, Russell S. Frye, John L.
                               4

Wittenborn, William L. Fang, Dell E. Perelman, Leslie A. Hulse,
Richard Wasserstrom, Harry M. Ng, Ralph J. Colleli, Jr., Jan S.
Amundson, Quentin Riegel, Robin S. Conrad, John T. Whatley,
Julie C. Becker, Douglas I. Greenhaus, Jed R. Mandel, Timothy
A. French, Robert G. Slaughter, Mark J. Washko, and Nick
Goldstein were on the brief of industry intervenors in support of
respondent.

   Daniel J. Popeo, Paul D. Kamenar, Peter Glaser, and
Douglas A. Henderson were on the brief of amicus curiae
Washington Legal Foundation in support of respondent.

    Edward W. Warren and Eric B. Wolff were on the brief of
amicus curiae John D. Dingell (D-Michgan) in support of denial
of petitions for review.

    Before: SENTELLE, RANDOLPH, and TATEL, Circuit Judges.

    Judgment of the Court filed by Circuit Judge RANDOLPH.

    Opinion filed by Circuit Judge RANDOLPH.

     Opinion dissenting in part and concurring in the judgment
filed by Circuit Judge SENTELLE.

    Opinion dissenting in Nos. 03-1361, 03-1362, 03-1363, and
03-1364 filed by Circuit Judge TATEL.

     RANDOLPH, Circuit Judge: Petitioners are twelve states,
three cities, an American territory, and numerous environmental
organizations. They are opposed by the Environmental
Protection Agency as respondent, and ten states and several
trade associations as intervenors. The controversy is about
EPA’s denial of a petition asking it to regulate carbon dioxide
(CO2) and other greenhouse gas emissions from new motor
                                 5

vehicles under § 202(a)(1) of the Clean Air Act, 42 U.S.C.
§ 7521(a)(1). EPA concluded that it did not have statutory
authority to regulate greenhouse gas emissions from motor
vehicles and that, even if it did, it would not exercise the
authority at this time. 68 Fed. Reg. 52,922 (Sept. 8, 2003).

                                 I.

     We should say a few words about our jurisdiction under the
Clean Air Act to review an EPA denial of a petition for
rulemaking. Section 307(b)(1), 42 U.S.C. § 7607(b)(1), gives
this court exclusive jurisdiction over “nationally applicable
regulations promulgated, or final action taken, by the
Administrator” under chapter 85 of the Act. The district courts,
on the other hand, have jurisdiction over citizen suits to compel
EPA to perform nondiscretionary acts or duties. 42 U.S.C.
§ 7604(a)(2); see Sierra Club v. Thomas, 828 F.2d 783, 787-92
(D.C. Cir. 1987). Because EPA refused to promulgate
“nationally applicable regulations” after being asked to do so,
we have jurisdiction only if EPA thereby engaged in “final
action.” We can be sure that its denial of the rulemaking
petition was “final.” But did this constitute agency “action”?
To answer that question we must consult the Administrative
Procedure Act -- specifically 5 U.S.C. § 551(13). The term
“action” in § 307(b)(1) of the Clean Air Act, like the term
“final,” carries its traditional meaning in administrative law. See
Whitman v. Am. Trucking Ass’ns, 531 U.S. 457, 478 (2001);
Indep. Equip. Dealers Ass’n v. EPA, 372 F.3d 420, 428 (D.C.
Cir. 2004); Sierra Club v. Gorsuch, 715 F.2d 653, 656-57 (D.C.
Cir. 1983). Section 551(13) of the APA defines “agency action”
as “the whole or a part of an agency rule, order, license,
sanction, relief, or the equivalent or denial thereof, or failure to
act” (italics added). While § 307 of the Clean Air Act makes
several APA provisions inapplicable -- namely, 5 U.S.C. §§ 553-
557 & 706 -- APA § 551 is not among them. EPA’s denial of
                                6

the rulemaking petition was therefore “final action,” and since
the petition sought regulations national in scope, § 307(b)(1)
confers jurisdiction on this court to hear these consolidated
cases.

     Another, related, point needs to be mentioned. Several of
the petitions for judicial review treated a memorandum of EPA’s
General Counsel, Robert Fabricant, as “final action taken, by the
Administrator” under § 307(b)(1). The memorandum, dated
August 28, 2003, and addressed to the EPA Administrator, was
entitled “EPA’s Authority to Impose Mandatory Controls to
Address Global Climate Change under the Clean Air Act.” The
General Counsel, after analyzing § 202(a)(1) of the Clean Air
Act, and other legislative and executive actions, stated his belief
that the Act “does not authorize regulation to address global
climate change.”          He therefore withdrew a contrary
memorandum issued in 1998 by one of his predecessors.

     The Fabricant memorandum, consisting of legal advice to
the EPA Administrator, did not in itself constitute “final action”
of the Administrator. To be sure, the Administrator adopted the
“General Counsel’s opinion” and relied on its analysis as one of
the alternative grounds for rejecting the rulemaking petition.
See 68 Fed. Reg. at 52,925. The Administrator’s explanation
incorporated many of the memorandum’s passages verbatim,
rephrased and reordered others, and expanded on the General
Counsel’s reasoning. Still, it is the Administrator’s denial of the
rulemaking petition, with the accompanying explanation, that
represents the “final action” of the Administrator subject to
judicial review under § 307(b)(1). The significance of the
General Counsel’s opinion, as set forth in his memorandum, is
the Administrator’s reliance on his reasoning in deciding the
matter now before us.
                                7

     There is an additional jurisdictional issue presented, but not
under the Clean Air Act. EPA claims that petitioners lack
standing under Article III of the Constitution. Standing exists
only if the complainant has suffered an injury in fact, fairly
traceable to the challenged action, and likely to be redressed by
a favorable decision. See Lujan v. Defenders of Wildlife, 504
U.S. 555, 560 (1992). EPA’s argument is that petitioners have
not “adequately demonstrated” two elements of standing: that
their alleged injuries were “caused by EPA’s decision not to
regulate emissions of greenhouse gases from mobile sources”;
and that their injuries “can be redressed by a decision in their
favor” by this court. Brief for Respondent at 16.

     In anticipation of this argument, petitioners filed two
volumes of declarations with the court, some containing lengthy
exhibits. The declarations, from scientists, engineers, state
officials, homeowners, users of the nation’s recreational
resources, and other individuals, predict catastrophic
consequences from global warming caused by greenhouse gases,
including loss of or damage to state and private property,
frequent intense storm surge floods, and increased health care
costs. Brief for Petitioners at 2-4.

     For the causation and redressability aspects of standing,
petitioners cite two of their declarations. One, from a
climatologist, states that reductions in CO2 and other greenhouse
gases from vehicles in the United States would alone have a
meaningful impact and would “delay and moderate many of the
adverse impacts of global warming.” He adds that if EPA took
action to reduce such emissions, other countries would likely
follow suit. The climatologist bases his predictions about future
climate change on climate models and on “quantitative scenarios
generated by the IPCC” -- the Intergovernmental Panel on
Climate Change, established in 1988 by the United Nations and
the World Meteorological Organization. The other declaration
                                8

is from a mechanical engineer. He states that, on the basis of his
experience with controlling other pollutants, there is “no doubt
that establishing emissions standards for pollutants that
contribute to global warming would lead to investment in
developing improved technologies to reduce those emissions
from motor vehicles, and that successful technologies would
gradually be mandated by other countries around the world.”

     We have held that, to establish standing, a petitioner
challenging agency action has the same burden of production as
“a plaintiff moving for summary judgment in the district court:
it must support each element of its claim to standing ‘by
affidavit or other evidence.’” Sierra Club v. EPA, 292 F.3d 895,
899 (D.C. Cir. 2002) (quoting Lujan, 504 U.S. at 561).
Petitioners’ declarations do “support each element” of standing.
But supporting an allegation is one thing; proving an allegation
is quite another. Lujan holds that when a plaintiff’s standing is
challenged in a motion for summary judgment, the plaintiff
“must ‘set forth’ by affidavit or other evidence ‘specific facts,’
Fed. Rule Civ. Proc. 56(e), which for purposes of the summary
judgment motion will be taken as true.” 504 U.S. at 561. If we
were to analogize the situation here to one in which EPA filed
such a summary judgment motion, we would conclude that
petitioners had submitted enough evidence raising genuine
issues of material fact to defeat the motion. See FED. R. CIV. P.
56©. But Lujan goes on to hold that at “the final stage” the
evidence plaintiff presented at summary judgment “(if
controverted) must be ‘supported adequately by the evidence
adduced at trial.’” 504 U.S. at 561 (quoting Gladstone, Realtors
v. Village of Bellwood, 441 U.S. 91, 115 n.31 (1979)). One
might say that in this case we are at the “final stage.” But the
analogy is not entirely apt. As an appellate court we do not
conduct evidentiary hearings in order to make findings of fact.
This is why, when Sierra Club spoke of “other evidence”
relating to standing, the court had in mind evidence presented to
                               9

the agency. 292 F.3d at 899. Here, the administrative record
contains a wealth of such “other evidence,” and some of it
contradicts petitioners’ claim that greenhouse gas emissions
from new motor vehicles have caused or will cause a significant
change in the global climate. That is partly why EPA decided
not to regulate at this time.

     Steel Co. v. Citizens for a Better Environment, 523 U.S. 83
(1998), instructs federal courts to resolve Article III standing
questions before proceeding to the merits of a case. The
combination of Lujan, Steel Co., and the factual overlap of the
standing issues with EPA’s justifications for not regulating
greenhouse gases present us with three options. The first is to
refer the standing issues to a special master for a factual
determination. This would be, as one commentator has
suggested, “folly.” 13A CHARLES A. WRIGHT ET AL., FEDERAL
PRACTICE AND PROCEDURE 2D § 3531.15, at 101 (1984). Such
a proceeding would largely duplicate the proceedings on the
rulemaking petition and to no good end. Another option would
be to remand to EPA for a factual determination of causation
and redressability. That too would make no sense. For one
thing, judgments about standing are the responsibility of the
federal courts. For another, EPA has already reached a decision
about the state of the evidence regarding global warming from
greenhouse gases. The third option is to proceed to the merits
with respect to EPA’s alternative decision not to regulate on the
grounds, among others, that the effect of greenhouse gases on
climate is unclear and that models used to predict climate
change might not be accurate.

     We have decided to follow the third course. Steel Co.
endorses this approach with respect to questions of statutory
standing. The Court explained that “the merits inquiry and the
statutory standing inquiry often overlap” and “are sometimes
identical, so that it would be exceedingly artificial to draw a
                                 10

distinction between the two.” 523 U.S. at 97 n.2. The Court’s
distinction of Article III standing cases rested on the premise
that there would be no such overlap and that the issue of Article
III standing would be entirely separate from the merits. Id. The
Court did not say what the proper order of decision should be
when, as in this case, that premise does not hold. In this highly
unusual circumstance -- encountered for the first time in this
court -- we will follow the statutory standing cases. We will
therefore assume arguendo that EPA has statutory authority to
regulate greenhouse gases from new motor vehicles.1 The
question we address is whether EPA properly declined to
exercise that authority.

                                 II.

     Greenhouse gases trap energy, much like the glass panels of
a greenhouse. The earth’s surface is warmed by absorbing solar
energy (visible light). The earth, in turn, radiates infrared energy
(heat) back into space. A portion of the infrared radiation is
trapped by greenhouse gas molecules, resulting in additional
warming of the lower atmosphere and the earth’s surface. This
“greenhouse effect” is a natural phenomenon, without which the
planet would be significantly colder and life as we know it
would not be possible. EPA, Global Warming -- Climate, at
http://yosemite.epa.gov/oar/globalwarming.nsf/content/climat
e.html.



        1
          Relying on FDA v. Brown & Williamson Tobacco Corp., 529
U.S. 120 (2000), EPA concluded that in light of the enormous
economic and political consequences of regulating greenhouse gas
emissions, Congress would have been far more specific if it had
intended to authorize EPA to regulate the subject under § 202(a)(1) of
the Clean Air Act. 58 Fed. Reg. at 52,928. We express no view on
the validity of EPA’s analysis.
                               11

     Petitioners sought to have EPA regulate, under § 202(a)(1)
of the Clean Air Act, carbon dioxide (CO2), and three other
greenhouse gases: methane (CH4), nitrous oxide (N2O), and
hydrofluorocarbons (HFCs).2 In response to EPA’s request for
public comments on the 1999 petition for rulemaking, the
agency received nearly 50,000 submissions. 68 Fed. Reg. at
52,924. Most were short expressions of support for the petition;
many were nearly identical. Id. The comment period closed in
May 2001. In the same month, the White House requested the
National Academy of Sciences to assist the Administration in its
review of climate change policy. The Academy “is a private,
nonprofit, self-perpetuating society of distinguished scholars
engaged in scientific and engineering research . . . .” NATIONAL
RESEARCH COUNCIL, CLIMATE CHANGE SCIENCE: AN ANALYSIS
OF SOME OF THE KEY QUESTIONS, preface (2001). Under its
congressional charter, issued in 1863, the Academy has a
mandate to advise the federal government on scientific and
technical matters when requested. The Academy’s principal
operating agency for providing such advice is its National
Research Council. Id.

     In denying the rulemaking petition, EPA found that the
scientific comments petitioners and others submitted rested on
information already in the public domain and did not add
significantly to the body of knowledge available to the National
Research Council when it prepared the report cited above. Since
none of the comments caused EPA to question the Council’s
report, EPA decided to rely on the Council’s “objective and
independent assessment of the relevant science.” 68 Fed. Reg.
at 52,930.




       2
          The rulemaking request and the papers submitted to this
court focus on the effects of CO2.
                                  12

     The National Research Council concluded that “a causal
linkage” between greenhouse gas emissions and global warming
“cannot be unequivocally established.” NATIONAL RESEARCH
COUNCIL, CLIMATE CHANGE SCIENCE, at 17. The earth
regularly experiences climate cycles of global cooling, such as
an ice age, followed by periods of global warming. Id. at 7.
Global temperatures have risen since the industrial revolution,
as have atmospheric levels of carbon dioxide. But an increase
in carbon dioxide levels is not always accompanied by a
corresponding rise in global temperatures. For example,
although carbon dioxide levels increased steadily during the
twentieth century, global temperatures decreased between 1946
and 1975. Id. at 16. Considering this and other data, the
National Research Council concluded that “there is considerable
uncertainty in current understanding of how the climate system
varies naturally and reacts to emissions of greenhouse gases.”
Id. at 1. This uncertainty is compounded by the possibility for
error inherent in the assumptions necessary to predict future
climate change.3 And, as the National Research Council noted,


        3
            “As the NRC explained, predicting future climate change
necessarily involves a complex web of economic and physical factors
including: Our ability to predict future global anthropogenic emissions
of GHGs and aerosols; the fate of these emissions once they enter the
atmosphere (e.g., what percentage are absorbed by vegetation or are
taken up by the oceans); the impact of those emissions that remain in
the atmosphere on the radiative properties of the atmosphere; changes
in critically important climate feedbacks (e.g., changes in cloud cover
and ocean circulation); changes in temperature characteristics (e.g.,
average temperatures, shifts in daytime and evening temperatures);
changes in other climatic parameters (e.g., shifts in precipitation,
storms); and ultimately the impact of such changes on human health
and welfare (e.g., increases or decreases in agricultural productivity,
human health impacts). The NRC noted, in particular, that ‘[t]he
understanding of the relationships between weather/climate and
human health is in its infancy and therefore the health consequences
                                  13

past assumptions about effects of future greenhouse gas
emissions have proven to be erroneously high. Id. at 19.

     Relying on Ethyl Corp. v. EPA, 541 F.2d 1 (D.C. Cir. 1976)
(en banc), petitioners challenge EPA’s decision to forego
rulemaking “[u]ntil more is understood about the causes, extent
and significance of climate change and the potential options for
addressing it.” 68 Fed. Reg. at 52,931. In our view Ethyl
supports EPA, not petitioners. Section 202(a)(1) directs the
Administrator to regulate emissions that “in his judgment” “may
reasonably be anticipated to endanger public health or welfare.”
Section 202(a)(1) was not at issue in Ethyl; the court mentioned
an earlier version of that provision, in a footnote, only by way
of analogy. 541 F.2d at 20 n.37. But what the court had to say
about § 202(a)(1) is instructive. In requiring the EPA
Administrator to make a threshold “judgment” about whether to
regulate, § 202(a)(1) gives the Administrator considerable
discretion. Id. Congress does not require the Administrator to
exercise his discretion solely on the basis of his assessment of
scientific evidence. Id. at 20. What the Ethyl court called
“policy judgments” also may be taken into account. By this the
court meant the sort of policy judgments Congress makes when
it decides whether to enact legislation regulating a particular
area. Id. at 26.

    The EPA Administrator’s analysis, although it did not
mention Ethyl, is entirely consistent with the case. In addition
to the scientific uncertainty about the causal effects of


of climate change are poorly understood’ (p. 20). Substantial scientific
uncertainties limit our ability to assess each of these factors and to
separate out those changes resulting from natural variability from
those that are directly the result of increases in anthropogenic GHGs.”
68 Fed. Reg. at 52,930.
                                14

greenhouse gases on the future climate of the earth, the
Administrator relied upon many “policy” considerations that, in
his judgment, warranted regulatory forbearance at this time. 68
Fed. Reg. at 52,929. New motor vehicles are but one of many
sources of greenhouse gas emissions; promulgating regulations
under § 202 would “result in an inefficient, piecemeal approach
to the climate change issue.” 68 Fed. Reg. at 52,931. The
Administrator expressed concern that unilateral regulation of
U.S. motor vehicle emissions could weaken efforts to persuade
developing countries to reduce the intensity of greenhouse gases
thrown off by their economies. Id. Ongoing research into
scientific uncertainties and the Administration’s programs to
address climate change -- including voluntary emission
reduction programs and initiatives with private entities to
develop new technology -- also played a role in the
Administrator’s decision not to regulate. 68 Fed. Reg. at
52,931-33. The Administrator pointed to efforts to promote
“fuel cell and hybrid vehicles” and ongoing efforts to develop
“hydrogen as a primary fuel for cars and trucks.” 68 Fed. Reg.
at 52,931. The Administrator also addressed the matter of
remedies. Petitioners offered two ways to reduce CO2 from new
motor vehicles: reduce gasoline consumption and improve tire
performance. As to the first, the Department of Transportation
-- the agency in charge of fuel efficiency standards -- recently
issued new standards requiring greater fuel economy, as a result
of which millions of metric tons of CO2 will never reach the
stratosphere. Id. As to tire efficiency, EPA doubted its
authority to regulate this subject as an “emission” of an air
pollutant. Id. “With respect to the other [greenhouse gases] --
CH4, N2O, and HFCs -- petitioners make no suggestion as to
how those emissions might be reduced from motor vehicles.”
Id.

   It is therefore not accurate to say, as petitioners do, that the
EPA Administrator’s refusal to regulate rested entirely on
                               15

scientific uncertainty, or that EPA’s decision represented an
“open-ended invocation of scientific uncertainty to justify
refusing to regulate,” Brief for Petitioners at 51.              A
“determination of endangerment to public health,” the court said
in Ethyl, “is necessarily a question of policy that is to be based
on an assessment of risks and that should not be bound by either
the procedural or the substantive rigor proper for questions of
fact.” Ethyl, 541 F.2d at 24. And as we have held, a reviewing
court “will uphold agency conclusions based on policy
judgments” “when an agency must resolve issues ‘on the
frontiers of scientific knowledge.’” Envtl. Def. Fund v. EPA,
598 F.2d 62, 82 (D.C. Cir. 1978).

     We thus hold that the EPA Administrator properly
exercised his discretion under § 202(a)(1) in denying the petition
for rulemaking. The petitions for review in Nos. 03-1365, 03-
1366, 03-1367, and 03-1368 are dismissed, and the petitions for
review in Nos. 03-1361, 03-1362, 03-1363, and 03-1364 are
denied.

                                                     So ordered.
      SENTELLE, Circuit Judge, dissenting in part and concurring
in the judgment: As the majority’s opinion observes, courts of
the United States must resolve jurisdictional questions, including
“Article III standing questions, before proceeding to the merits
of a case.” Opinion of Judge Randolph at 9 (citing Steel Co. v.
Citizens for a Better Environment, 523 U.S. 83 (1998)). As the
majority further observes, “[s]tanding exists only if the
complainant has suffered an injury in fact, fairly traceable to the
challenged action, and likely to be redressed by a favorable
decision.” Id. at 6-7 (citing Lujan v. Defenders of Wildlife, 504
U.S. 555, 560 (1992)). EPA argues “that petitioners have not
‘adequately demonstrated’ two elements of standing: that their
alleged injuries were ‘caused by EPA’s decision not to regulate
emissions of greenhouse gases from mobile sources’; and that
their injuries ‘can be redressed by a decision in their favor’ by
this court.” Id. at 7 (quoting Brief for Respondent at 16). While
I respect the majority’s thorough and accurate history of the
precedents on the standing question, after consulting the same
authorities I have come to a different conclusion. I conclude
that EPA is correct in its assertion that the petitioners have not
demonstrated the element of injury necessary to establish
standing under Article III.

                            I. Injury

     As the Supreme Court has stated quite directly and
succinctly:

    It is an established principle that to entitle a private
    individual to invoke the judicial power to determine the
    validity of executive or legislative action he must show that
    he has sustained or is immediately in danger of sustaining
    a direct injury as the result of that action and it is not
    sufficient that he has merely a general interest common to
    all members of the public.
                                 2

Ex Parte Levitt, 302 U.S. 633 (1937) (citing Tyler v. Judges, 179
U.S. 405, 406 (1900); Southern Ry. Co. v. King, 217 U.S. 524,
534 (1910); Newman v. Frizzell, 238 U.S. 537, 549, 550 (1915);
Fairchild v. Hughes, 258 U.S. 126, 129 (1922); Massachusetts
v. Mellon, 262 U.S. 447, 488) (1923)).

      Thus, the courts “have consistently held that a plaintiff
raising only a generally available grievance about government
– claiming only harm to his and every citizen’s interest in proper
application of the Constitution and laws, and seeking relief that
no more directly and tangibly benefits him than it does the
public at large – does not state an Article III case or
controversy.” Lujan, 504 U.S. at 573. Or, as the Supreme Court
has also put it, to establish Article III standing a “plaintiff must
have suffered an ‘injury in fact’– an invasion of a legally
protected interest which is (a) concrete and particularized . . .
and (b) actual or imminent, not conjectural or hypothetical.” Id.
at 560 (emphasis added; citations and internal quotation marks
omitted). Most tellingly, the Supreme Court has specifically
declared that “[b]y particularized, we mean that the injury must
affect the plaintiff in a personal and individual way.” Id. at n.1.
In the case before us, that is what the petitioners have not
established. After plowing through their reams of affidavits and
arguments, I am left with the unshaken conviction that they have
alleged and shown no harm particularized to themselves. As we
have observed in the context of determining standing even in a
procedural case, in which the standards are perhaps more
relaxed than in other cases, “in order to show that the interest
asserted is more than a mere ‘general interest . . . common to all
members of the public,’ the plaintiffs must show that the
government act . . . will cause a distinct risk to a particularized
interest of the plaintiff.” Florida Audubon Soc’y v. Bentsen, 94
F.3d 658, 664 (D.C. Cir. 1996).
                                3

     Petitioners’ allegations and affidavits, and petitioners’
argument and briefs, are all well made and sincere.
Nonetheless, even in the light most favorable to the petitioners,
in the end they come down to this: Emission of certain gases that
the EPA is not regulating may cause an increase in the
temperature of the earth – a phenomenon known as “global
warming.” This is harmful to humanity at large. Petitioners are
or represent segments of humanity at large. This would appear
to me to be neither more nor less than the sort of general harm
eschewed as insufficient to make out an Article III controversy
by the Supreme Court and lower courts.

      The courts under Article III stand ready to adjudicate and
redress the particularized injuries of plaintiffs, when all other
elements of jurisdiction are present. But “when the plaintiff is
not himself the object of the government action or inaction he
challenges, [although] standing is not precluded, . . . it is
ordinarily ‘substantially more difficult’ to establish.” Lujan,
504 U.S. at 562 (citations omitted). This time, in my view, it is
not only difficult, it is impossible. The generalized public good
that petitioners seek is the thing of legislatures and presidents,
not of courts. As we stated in another environmental case, to
ascertain standing courts must ask the question, did the
“underlying governmental act [or inaction] demonstrably
increase[] some specific risk of environmental harm to the
interest of the plaintiff”? Florida Audubon Soc’y, 94 F.3d at 667
(emphasis in original). Here, as in Florida Audubon, the alleged
harm is not particularized, not specific, and in my view, not
justiciable.

     Therefore, I would reject and dismiss all the petitions before
us. This is not to say that petitioners’ complaints are wrong.
This is not to say they are without redress. This is to say only
that the question is not justiciable in its present form with its
present champions in the present forum. A case such as this, in
                                 4

which plaintiffs lack particularized injury is particularly
recommended to the Executive Branch and the Congress.
Because plaintiffs’ claimed injury is common to all members of
the public, the decision whether or not to regulate is a policy call
requiring a weighing of costs against the likelihood of success,
best made by the democratic branches taking into account the
interests of the public at large. There are two other branches of
government. It is to those other branches that the petitioners
should repair.

               II. Concurrence in the Judgment

     My conclusion leaves a slight problem. No problem exists
as to the petitions for review of nonfinal action which Judge
Randolph’s opinion orders dismissed. I would dismiss those as
well, on either his ground or mine. The problem vexes only as
to petitions for review in Nos. 03-1361, 03-1362, 03-1363, and
03-1364, which Judge Randolph would deny and Judge Tatel
would grant. I would dismiss those as well, as I would hold that
we have no jurisdiction to either deny or grant them. How then
are we to reach a judgment?

      The Supreme Court has suggested a way, or at least Justices
of the Supreme Court have. Most recently, in Hamdi v.
Rumsfeld, 124 S. Ct. 2633 (2004), Justice Souter, joined by
Justice Ginsburg, differed from the plurality in a fragmented
opinion adjudicating the due process rights of alleged enemy
combatants held at Guantanamo Bay by the United States
military. Justices Souter and Ginsburg would have vacated the
judgment of the Court of Appeals and remanded for proceedings
consistent with their view that the government had failed to
justify holding the petitioner. However, because that view did
not command a majority of the court, and because of “the need
to give practical effect to the conclusion of [a majority] of the
court rejecting the government’s position,” Justice Souter
                                5

(joined by Justice Ginsburg) joined with the plurality “in
ordering a remand on terms closest to those I would impose.”
124 S. Ct. at 2660 (Souter, J., concurring). I will take a similar
course here.

      The majority today holds that we have jurisdiction to render
judgment on four of the petitions before us. Although I
disagree, I will accept the decision of the majority as dictating
the law of this case. Having so accepted the law of the case, I
will then join Judge Randolph in the issuance of a judgment
closest to that which I myself would issue.             With that
explanation, I join in the decision to order denying the four
petitions from final action of the Environmental Protection
Agency.
     TATEL, Circuit Judge, dissenting in Nos. 03-1361, 03-1362,
03-1363, and 03-1364: Petitioners claim that motor vehicle
emissions of greenhouse gases contribute to global warming and
that global warming in turn is causing a host of serious
problems, likely including increased flash flood potential in the
Appalachians, degraded water quality and reduced water supply
in the Great Lakes, sea-ice melting and permafrost thawing in
Alaska, reduced summer snow-pack runoff in the Rockies,
extreme water resource fluctuations in Hawaii, and rising sea
levels combined with higher storm surges along the coasts of
Puerto Rico, the Virgin Islands, and some eastern states. See
Pet’rs Br. at 8-10 (summarizing U.S. Dep’t of State, U.S.
Climate Action Report 2002, at 110). Concerned about such
problems, petitioners asked EPA to regulate these emissions
under Clean Air Act section 202(a)(1), which provides: “The
Administrator shall by regulation prescribe . . . standards
applicable to the emission of any air pollutant from . . . new
motor vehicles . . . which in his judgment cause, or contribute to,
air pollution which may reasonably be anticipated to endanger
public health or welfare.” 42 U.S.C. § 7521(a)(1). EPA denied
the petition on two grounds—that it lacked statutory authority to
regulate such emissions and that even given such authority it
would not exercise it—and petitioners sought review in this
court.
     My colleagues agree that the petitions for review should not
be granted, but they do so for quite different reasons. Judge
Sentelle thinks that petitioners lack standing and would dismiss
the petitions for that reason. Judge Randolph does not resolve
whether petitioners have standing and would deny the petitions
based on one of EPA’s two given reasons.
     I have yet a different view. Unlike Judge Sentelle, I think
at least one petitioner has standing, as I explain in Part II.
Unlike Judge Randolph, I think EPA’s order cannot be sustained
on the merits. EPA’s first given reason—that it lacks statutory
                                2

authority to regulate emissions based on their contribution to
welfare-endangering climate change, 68 Fed. Reg. 52,922,
52,925-29 (Sept. 8, 2003)—fails, as I explain in Part III, because
the statute clearly gives EPA authority to regulate “any air
pollutant” that may endanger welfare, 42 U.S.C. § 7521(a)(1),
with “air pollutant” defined elsewhere in the statute as
“including any physical, chemical, biological, radioactive . . .
substance or matter which is emitted into or otherwise enters the
ambient air,” id. § 7602(g). EPA’s second given reason—the
one accepted by Judge Randolph—is that even if it has statutory
authority, it nonetheless “believes” that “it is inappropriate to
regulate [greenhouse gas] emissions from motor vehicles” due
to various policy reasons. As I explain in Part IV, however,
none of these policy reasons relates to the statutory
standard—“cause, or contribute to, air pollution which may
reasonably be anticipated to endanger public health or welfare,”
id. § 7521(a)(1)—and the Clean Air Act gives the Administrator
no discretion to withhold regulation for such reasons.
     In short, EPA has failed to offer a lawful explanation for its
decision. I would accordingly grant the petitions for review and
send the matter back to EPA either to make an endangerment
finding or to come up with a reasoned basis for refusing to do so
in light of the statutory standard.

                                I.
     “Greenhouse gases are accumulating in Earth’s atmosphere
as a result of human activities, causing surface air temperatures
and subsurface ocean temperatures to rise.” So begins page one
of the National Research Council’s 2001 report, Climate Change
Science: An Analysis of Some of the Key Questions (“NRC
Report”), the scientific document EPA “rel[ied]” on in denying
the petition for rulemaking, see 68 Fed. Reg. at 52,930.
    As the NRC Report explains, greenhouse gases (GHGs) trap
heat radiated from earth, and their atmospheric concentrations
                                3

are increasing “as a result of human activities.” NRC Rep. at 1,
9. For example, “[h]uman activities . . . responsible for the
increase” in atmospheric concentrations of carbon dioxide
(CO2)—the chief GHG—include “[t]he primary source, fossil
fuel burning,” as well as “[t]ropical deforestation.” Id. at 2; see
also id. at 10, 12. The resulting increases are striking. In the
400,000 years prior to the Industrial Revolution, atmospheric
CO2 concentrations “typically ranged between 190” parts per
million by volume (ppmv) “during the ice ages to near 280
ppmv during the warmer ‘interglacial’ periods.” Id. at 11. By
1958, atmospheric concentrations were 315 ppmv (12.5% above
the pre-Industrial-Revolution high of 280 ppmv), and by 2000
they had risen to 370 ppmv (17% above the 1958 level). Id. at
10. Similarly, prior to the Industrial Revolution, atmospheric
concentrations of methane (CH4), another GHG, ranged from .3
ppmv to .7 ppmv; now, “current values are around 1.77 ppmv.”
Id. at 11. Atmospheric concentrations of other GHGs like
nitrous oxide (N2O) have also risen. Id. at 2. Notably, GHGs
not only disperse throughout the lower atmosphere, but also
linger there at length: “Reductions in the atmospheric
concentrations of these gases following possible lowered
emissions rates in the future will stretch out over decades for
methane, and centuries and longer for carbon dioxide and
nitrous oxide.” Id. at 10.
     Increased GHG atmospheric concentrations are causing
“climate forcings”—“imposed perturbation[s] of Earth’s energy
balance” measured in terms of units of watts per square meter
(W/m2). Id. at 6. Drawing from another report—an
Intergovernmental Panel on Climate Change (IPCC) report with
which the NRC “generally agrees,” id. at 1—the NRC Report
quantifies these climate forcings. CO2, “probably the most
important climate forcing agent today,” has “caus[ed] an
increased forcing of about 1.4 W/m2” between 1750 and 2000.
Id. at 12, 13. More lies ahead:
                                4

    CO2 climate forcing is likely to become more dominant in
    the future as fossil fuel use continues. If fossil fuels
    continue to be used at the current rate, the added CO2
    forcing in 50 years will be about 1 W/m2. If fossil fuel use
    increases by 1-1.5% per year for 50 years, the added CO2
    forcing instead will be about 2 W/m2.
Id. at 12-13. Thus, by 2050, the total CO2 forcing since 1750
could be from 2.4-3.4 W/m2. The other GHGs “together cause
a climate forcing approximately equal to that of CO2,” or more
if one includes certain indirect effects of increased CH4
emissions. Id. at 13. While atmospheric GHG increases are not
the only causes of climate forcings—for example, changes in
solar irradiance and in concentrations of tropospheric ozone also
appear to have caused climate forcings, and atmospheric
concentration changes in aerosols like sulphates appear to have
caused negative (cooling) climate forcings—all other forcings
are less certain and appear less substantial than those caused by
GHGs. See id.
     The extent to which these forcings affect average global
temperatures depends on the climate’s sensitivity, a condition
that is not precisely known. Id. at 7. “Well-documented climate
changes . . . imply that the climate sensitivity is near . . . 3ºC”
(5.4ºF) for a 4 W/m2 forcing—a number a bit above the total
CO2 forcing predicted by 2050—“but with a range from 1.5ºC
to 4.5ºC (2.7 to 8.1ºF).” Id.
    Turning to the practical effects of GHG climate forcings,
the NRC Report observes that a “diverse array of evidence
points to a warming of global surface temperatures.” Id. at 16.
Though the “rate of warming has not been uniform,”
measurements “indicate that global mean surface air temperature
warmed by about .4-.8ºC (.7-1.5ºF) during the 20th century.” Id.
The report notes that “[t]he Northern Hemisphere as a whole
experienced a slight cooling from 1946-75,”—a statement Judge
Randolph erroneously reads for the proposition that “global
                                5

temperatures decreased between 1946 and 1975,” op. of
Randolph, J., at 12 (emphasis added)—possibly due to the
widespread burning of high sulfur coal and resultant sulfate
emissions or to changes in ocean circulation in the Atlantic.
NRC Rep. at 16. The report also observes that, as the IPCC
report points out, the “warming of the Northern Hemisphere
during the 20th century is likely to have been the largest of any
century in the past thousand years.” Id.
     In evaluating the relationship between GHG atmospheric
increases and twentieth-century temperature increases, the NRC
Report states that due to the
    large and still uncertain level of natural variability inherent
    in the climate record and the uncertainties in the time
    histories of various forcing agents (and particularly
    aerosols), a causal linkage between the buildup of
    greenhouse gases in the atmosphere and the observed
    climate changes during the 20th century cannot be
    unequivocally established.
Id. at 17.       Although Judge Randolph seizes on this
uncertainty—and portrays it as applying to global warming
generally rather than to twentieth-century warming, see op. of
Randolph, J., at 11—read in context, it appears little more than
an application of the principle that, as the NRC Report later puts
it, “[c]onfidence limits and probabilistic information, with their
basis, should always be considered as an integral part of the
information that climate scientists provide to policy and decision
makers,” NRC Rep. at 22. Indeed, the NRC Report goes on to
state that the “fact that the magnitude of the observed warming
is large compared to natural variability as simulated in climate
models is suggestive of such a linkage” between GHG
atmospheric concentration increases and twentieth-century
temperature increases, though not “proof” of it. Id. at 17.
    The NRC Report further suggests that uncertainties about
                                6

future warming relate chiefly to its scope.
    Climate change simulations for the period of 1990 to 2100
    based on IPCC emissions scenarios yield a globally-
    averaged surface temperature increase by the end of the
    century of 1.4 to 5.8ºC (2.5 to 10.4ºF) relative to 1990. The
    wide range of uncertainty in these estimates reflects both
    the different assumptions about future concentrations of
    greenhouse gases and aerosols in the various scenarios
    considered by the IPCC and the differing climate
    sensitivities of the various climate models used in the
    simulations. The range of climate sensitivities implied by
    these predictions is generally consistent with previously
    reported values.
Id. at 3. These numbers, of course, are averages: the “predicted
warming is higher over higher latitudes than low latitudes,
especially during winter and spring, and larger over land than
over sea.” Id.
     With this warming will come secondary effects. Predicted
impacts in the United States include increased likelihood of
drought, greater heat stress in urban areas, rising sea levels, and
disruption to many U.S. ecosystems. Id. at 19-20. The
likelihood and scope of these impacts vary depending on the
magnitude of future temperature increases. See id.; see also id.
at 4. Because the “predicted temperature increase is sensitive to
assumptions concerning future concentrations of greenhouse
gases and aerosols,” which in turn depend on future emissions,
“national policy decisions made now and in the longer-term
future will influence the extent of any damage suffered by
vulnerable human populations and ecosystems later in this
century.” Id. at 1.
                                 7

                                II.
     EPA claims petitioners lack standing to bring this case. To
reach the merits, however, we need determine only that one
petitioner has standing. See, e.g., Nuclear Energy Inst., Inc. v.
EPA, 373 F.3d 1251, 1266 (D.C. Cir. 2004). In my view,
declarations submitted by petitioners clearly establish that the
Commonwealth of Massachusetts has satisfied each element of
Article III standing—injury, causation, and redressability, see,
e.g., Lujan v. Defenders of Wildlife, 504 U.S. 555, 560-61
(1992).
     Among other things, Massachusetts claims injury—the
“substantial probability that local conditions will be adversely
affected,” Sierra Club v. EPA, 292 F.3d 895, 898 (D.C. Cir.
2002) (internal quotation marks omitted)—resulting from rising
sea levels. The declaration of Paul Kirshen, a professor at Tufts
University’s Civil and Environmental Engineering Department,
details how projected rises in sea levels in the metropolitan
Boston area would lead both to permanent loss of coastal land
and to “more frequent and severe storm surge flooding events
along the coast.” Kirshen Decl. ¶¶ 7-8; see also Jacqz Decl. ¶¶
8-11. “[I]f sea level rises .3 meters (11.8 inches)—which is near
the lower end of the likely range—that would mean the future
10-year flood surge elevation would be at the level of the current
100-year flood elevation and the future 100-year flood surge
elevation would be at that of the current 500-year flood
elevation.” Kirshen Decl. ¶ 10. As other declarations make
clear, such changes would lead to serious loss of and damage to
Massachusetts’s coastal property. See Hoogeboom Decl. ¶¶ 6-7;
Jacqz Decl. ¶ 11.
     Given these declarations, I disagree that no petitioner
suffers “harm particularized to” itself. See op. of Sentelle, J., at
2.    The Commonwealth of Massachusetts claims an
injury—namely, loss of land within its sovereign
boundaries—that “affects [it] in a personal and individual way,”
                                 8

Lujan, 504 U.S. at 560 n.1. This loss (along with increased
flood damage to the Massachusetts coast) undeniably harms the
Commonwealth in a way that it harms no other state. Other
states may face their own particular problems stemming from
the same global warming—Maine may suffer from loss of
Maine coastal land and New Mexico may suffer from reduced
water supply—but these problems are different from the injuries
Massachusetts faces. Massachusetts’s harm is thus a far cry
from the kind of generalized harm that the Supreme Court has
found inadequate to support Article III standing, i.e., “harm to
[its] and every citizen’s interest in proper application of the
Constitution and laws,” or put another way “relief that no more
directly and tangibly benefits [it] than it does the public at
large,” id. at 573-74.
     As to causation, the declaration of Michael MacCracken,
the senior scientist on global change at the Office of the U.S.
Global Change Research Program from 1993-2002, states that
global warming is causing sea level increases like those in
Massachusetts. “[T]he warming of the oceans and the increased
melting of many mountain glaciers around the world . . . were
the major contributions to the rise in global sea level by 10-20
cm (4 to 8 inches) observed over the past century” and the
“environmental impacts of projected global warming will
include . . . an increase in sea level at an average rate of about .5
to 3.5 inches per decade, reaching 4-35 inches by the end of the
century (with the most likely value being, in my expert opinion,
near or above the middle of this range).” MacCracken Decl. ¶
5(c)-(d); see also id. ¶ 23. MacCracken further states that global
warming is chiefly triggered by human-caused GHG emissions,
see id. ¶¶ 5(a)-(b), 12-19, with “the U.S. transportation sector
(mainly automobiles) . . . responsible for about 7% of global
fossil fuel emissions,” id. ¶ 31.
     Finally, as to redressability, MacCracken emphasizes that
“[a]chievable reductions in emissions of CO2 and other [GHGs]
                                9

from U.S. motor vehicles would . . . delay and moderate many
of the adverse impacts of global warming.” Id. ¶5(e).
Elaborating, he states that “[g]iven the large emissions of CO2
and other [GHGs] from motor vehicles in the United States and
the lead time needed to economically introduce changes into the
motor vehicle fleet, emission reductions must be initiated in the
near future in order to significantly reduce and delay the impacts
of global warming.” Id. ¶ 31. Because the extent of damage to
the Massachusetts coastline depends on the magnitude of the
rise in sea level, a reduction in this projected adverse
consequence of global warming would partially redress
Massachusetts’s injury. See Tozzi v. U.S. Dep’t of Health &
Human Servs., 271 F.3d 301, 310 (D.C. Cir. 2001) (holding that
a petitioner need only demonstrate it would receive “at least
some” relief to establish redressability). Nowhere disputing this
proposition, EPA instead claims that MacCracken’s conclusion
depends upon the assumption that other countries will follow the
U.S. lead and regulate motor vehicle GHG emissions. Even
were this reading of the declaration correct—a dubious premise
given MacCracken’s unqualified language focusing on U.S.
emissions reduction—the uncontested declaration of Michael
Walsh, a consultant on motor vehicle pollution technology and
at one point director of EPA’s motor vehicle pollution control
efforts, provides a basis for concluding that other countries
would come to mandate technology developed in response to
U.S. regulation. Describing how in the past other countries have
come to require such technology, Walsh concludes that “[o]n the
basis of my experience with the control of other pollutants . . .
I have no doubt that establishing emissions standards for
pollutants that contribute to global warming would lead to
investment in developing improved technologies to reduce those
emissions from motor vehicles, and that successful technologies
would gradually be mandated by other countries around the
world.” Walsh Decl. ¶¶ 7-8, 10.
    Judge Randolph, accepting that the declarations “do
                                10

‘support each element’ of standing,” nonetheless questions
whether this is enough. See op. of Randolph, J., at 8 (quoting
Sierra Club, 292 F.3d at 899). Specifically, he believes we
confront a question left open in our Sierra Club decision. In that
case, we held that “[t]he petitioner’s burden of production in the
court of appeals is . . . the same as that of a plaintiff moving for
summary judgment in the district court: it must support each
element of its claim to standing ‘by affidavit or other
evidence.’” 292 F.3d at 899 (quoting Lujan, 504 U.S. at 561).
But we never explicitly addressed what happens if the agency
submits evidence that contradicts that of petitioners. Do we
resolve factual disputes in petitioners’ favor, return the case to
the agency for fact-finding, send the matter to a special master,
or pursue some other course of action?
     The issue is fascinating, but we need not confront it. Given
that the burdens of production here are comparable to those at
summary judgment, see 292 F.3d at 899, if EPA wants to
challenge the facts petitioners have set forth in their affidavits,
it has an obligation to respond to the petitioners by “citing any
record evidence relevant to . . . standing and, if necessary,
appending to its filing additional affidavits or other evidence,”
see id. at 900-01. EPA makes no such challenge.
     Indeed, if anything, the order under review appears to
support petitioners’ standing. While, drawing on the NRC
Report, EPA observes that “there continue to be important
uncertainties in our understanding of the factors that may affect
future climate change,” 68 Fed. Reg. at 52,930, EPA never
denies the “substantial probability,” see Sierra Club, 292 F.3d
at 898, that injurious global warming is occurring. Quite to the
contrary, EPA “agree[s] with the President that ‘we must
address the issue of global climate change.’” 68 Fed. Reg. at
52,929 (quoting presidential statement of Feb. 14, 2002). As to
causation and redressability, the petition denial emphasizes that
“EPA is also working to encourage voluntary GHG emission
                                11

reductions from the transportation sector” and that “the
Administration’s global climate change policy includes
promoting the development of fuel-efficient motor vehicles and
trucks, researching options for producing cleaner fuels, and
implementing programs to improve energy efficiency.” Id. at
52,932; see also NRC Rep. at 1 (noting that “national policy
decisions made now . . . will influence the extent of any
damage” caused by global warming). EPA would presumably
not bother with such efforts if it thought emissions reductions
would have no discernable impact on future global warming.
      Because EPA nowhere challenges petitioners’ declarations,
I see no reason to consider what we would do if it had done so.
Thus, unlike Judge Randolph, I think it unnecessary to address
whether we can carve out exceptions to the Supreme Court’s
seemingly unqualified holding that “a merits question cannot be
given priority over an Article III question,” Steel Co. v. Citizens
for a Better Env’t, 523 U.S. 83, 97 n.2 (1998). The
Commonwealth of Massachusetts has adequately demonstrated
its standing, and our jurisdiction is plain.

                               III.
     As to the merits, the threshold question is this: does the
Clean Air Act authorize EPA to regulate emissions based on
their effects on global climate? Taking a constricted view, EPA
insists it has no authority to regulate GHG emissions even if
they contribute to substantial and harmful global warming. By
contrast, petitioners claim that Congress has plainly given EPA
the authority it says it lacks.
    “If a court, employing traditional tools of statutory
construction, ascertains that Congress had an intention on the
precise question at issue, that intention is the law and must be
given effect.” Chevron U.S.A., Inc. v. Natural Res. Def.
Council, Inc., 467 U.S. 837, 843 n.9 (1984). The inquiry
“begin[s], as always, with the plain language of the statute in
                                12

question.” Consumer Elecs. Ass’n v. FCC, 347 F.3d 291, 297
(D.C. Cir. 2003) (quoting Citizens Coal Council v. Norton, 330
F.3d 478, 482 (D.C. Cir. 2003)). CAA section 202(a)(1), added
by Congress in 1965 and amended in 1970 and 1977, provides,
    The Administrator shall by regulation prescribe . . .
    standards applicable to the emission of any air pollutant
    from any class or classes of new motor vehicles or new
    motor vehicle engines which in his judgment cause, or
    contribute to, air pollution which may reasonably be
    anticipated to endanger public health or welfare.
42 U.S.C. § 7521(a)(1). This language plainly authorizes
regulation of (1) any air pollutants emitted from motor vehicles
that (2) in the Administrator’s judgment cause, or contribute to,
air pollution which may reasonably be anticipated to endanger
public health or welfare. EPA’s claimed lack of authority
relates to the first of these two elements. According to EPA,
GHGs like CO2, CH4, N2O, and hydrofluorocarbons (HFCs) “are
not air pollutants.” 68 Fed. Reg. at 52,928.
   Congress, however, left EPA little discretion in determining
what are “air pollutants.” Added in 1970 and amended in 1977,
CAA section 302(g) defines the term as follows:
    The term ‘air pollutant’ means any air pollution agent or
    combination of such agents, including any physical,
    chemical, biological, radioactive . . . substance or matter
    which is emitted into or otherwise enters the ambient air.
42 U.S.C. § 7602(g). This exceedingly broad language plainly
covers GHGs emitted from motor vehicles: they are “physical
[and] chemical . . . substance[s] or matter . . . emitted into . . .
the ambient air.” Indeed, in one CAA provision, added in 1990,
Congress explicitly included CO2 in a partial list of “air
pollutants.” Section 103(g) instructs the Administrator to
research “nonregulatory strategies and technologies for
preventing or reducing multiple air pollutants, including sulfur
                                13

oxides, nitrogen oxides, heavy metals, PM-10 (particulate
matter), carbon monoxide, and carbon dioxide.” Id. § 7403(g)
(emphasis added). Faced with such language, a court—as well
as an agency—would normally end the analysis here and
conclude that GHGs are “air pollutants,” since “[w]e ‘must
presume that a legislature says in a statute what it means and
means in a statute what it says . . . . When the words of a statute
are unambiguous . . . this first canon is also the last: judicial
inquiry is complete.’” Teva Pharm. Indus. Ltd. v. Crawford,
410 F.3d 51, 53 (D.C. Cir. 2005) (quoting Conn. Nat’l Bank v.
Germain, 503 U.S. 249, 253-54 (1992)) (omissions in original).
     Unswayed by what it calls “narrow semantic analyses,”
Resp’t Br. at 55—but what courts typically call Chevron step
one—EPA claims that a “more holistic analysis . . . [of] the text,
structure, and history of the CAA as a whole, as well as the
context provided by other legislation that is specific to climate
change,” justifies its conclusion that it cannot regulate GHGs
like CO2 for their effects on climate change, id. at 25-26. To
disregard the Act’s plain text in this way, EPA needs an
“extraordinarily convincing justification.” Appalachian Power
Co. v. EPA, 249 F.3d 1032, 1041 (D.C. Cir. 2001). “For the
EPA to avoid a literal interpretation at Chevron step one, it must
show either that, as a matter of historical fact, Congress did not
mean what it appears to have said, or that, as a matter of logic
and statutory structure, it almost surely could not have meant it.”
Engine Mfrs. Ass’n v. EPA, 88 F.3d 1075, 1089 (D.C. Cir.
1996).
     EPA offers four reasons for abandoning the Act’s text.
First, it suggests that since the 1965, 1970, and 1977 Congresses
were not specifically concerned with global warming, the Act
cannot apply to GHGs. Second, it claims that for both practical
and policy reasons, global pollution should be tackled through
specific statutory provisions rather than general ones. Third,
relying on FDA v. Brown & Williamson Tobacco Corp., 529
                               14

U.S. 120 (2000), it argues that Congress’s passage of legislation
calling for study of climate change, along with Congress’s
failure to pass any provisions tailored solely to regulating
GHGs, demonstrates that the CAA cannot apply to GHGs.
Finally, EPA suggests that Congress couldn’t have intended the
definition of “air pollutant” to cover CO2, since EPA regulation
of CO2 emissions from automobiles would overlap with
Department of Transportation (DOT) authority over fuel
economy standards under a different act. None of these reasons
provides a convincing justification—let alone an
“extraordinarily convincing” one—for EPA’s counter-textual
position.
     EPA first suggests that because the 1965, 1970, and 1977
Congresses showed little concern about the specific problem of
global warming, reading the CAA’s language to cover such
problems would be like finding “an elephant in a mousehole.”
Tr. of Oral Arg. at 32; see also Resp’t Br. at 23 (quoting
Whitman v. Am. Trucking Ass’ns, 521 U.S. 457, 468 (2002)).
EPA is correct that those Congresses spilled little ink on the
issue of global warming: while the legislative history contains
a few stray references to human-forced climate change, see, e.g.,
111 Cong. Rec. 25,061 (Sept. 24, 1965) (statement of Rep.
Helstoski); 116 Cong. Rec. 32,914 (Sept. 21, 1970) (report
introduced in the record by Sen. Boggs), in those years the
scientific understanding of the issue was nascent at best, see,
e.g., Environmental Quality: The First Annual Report of the
Council on Environmental Quality 93 (1970) (noting that “[m]an
may be changing his weather” but expressing uncertainty as to
whether global warming or cooling was occurring). But EPA
errs in suggesting that because Congress may not have precisely
foreseen global warming, the Act provides no authorization for
GHG regulation. Hardly a mousehole, the definition of “air
pollutants”—“including any physical, chemical, biological,
radioactive . . . substance or matter which is emitted into or
otherwise enters the ambient air”—enables the Act to apply to
                               15

new air pollution problems as well as existing ones. “[T]he fact
that a statute can be applied in situations not expressly
anticipated by Congress,” the Supreme Court has explained,
“does not demonstrate ambiguity. It demonstrates breadth.”
PGA Tour, Inc. v. Martin, 532 U.S. 661, 689 (2001) (quoting
Pa. Dep’t of Corrections v. Yeskey, 524 U.S. 206, 212 (1998)).
Indeed, Congress expressly instructed EPA to be on the lookout
for climate-related problems in evaluating risks to “welfare.”
Section 302(h), added in 1970, explains that “[a]ll language
referring to effects on welfare includes, but is not limited to,
effects on soils, water, crops, vegetation, manmade materials,
animals, wildlife, weather, visibility, and climate.” 42 U.S.C. §
7602(h) (emphasis added).
     EPA’s second reason for its interpretation—that for
practical and policy reasons global warming should be dealt
with through specifically tailored statutes—likewise fails to
trump Congress’s plain language. It may well be that a statute
aimed solely at global warming would deal with the problem
more effectively than one aimed generally at air pollution. But
an agency may not “avoid the Congressional intent clearly
expressed in the [statutory] text simply by asserting that its
preferred approach would be better policy.” Engine Mfrs. Ass’n,
88 F.3d at 1089. Perhaps recognizing this point, EPA attempts
to link its policy arguments to the statute by claiming that
because the 1977 and 1990 Congresses enacted provisions
specific to another global pollution problem—depletion of
stratospheric ozone—we must infer that the Act’s general
provisions do not cover such global problems. Once again, EPA
makes much of very little. While the 1977 Congress did add
provisions aimed specifically at ozone depletion, it also made
clear that “[n]othing in this [ozone-specific] part shall be
construed to alter or affect the authority of the Administrator
under . . . any other provision of this Act.” Pub. L. No. 95-95,
§ 158, 91 Stat. 685, 730 (1977); see also H.R. Rep. No. 95-294,
at 102 (1977) (expressing the House Committee’s view that
                               16

EPA could already regulate emissions to protect stratospheric
ozone under an existing general provision of the CAA).
Similarly, I see nothing in the 1990 Congress’s enactment of
other provisions specific to stratospheric ozone protection, see
42 U.S.C. §§ 7671 to 7671q, indicating it thought EPA lacked
authority under general provisions like section 202 to regulate
emissions contributing to global pollution. This is particularly
true since that Congress also enacted provisions specific to
certain regional pollutants, see, e.g., id. §§ 7651 to 7651o (acid
rain control), which, pursuant to general CAA provisions, EPA
already had authority to regulate.
     EPA also attempts an unworkability argument. Its
argument goes like this: another part of the CAA provides that
the Administrator shall maintain a list of air pollutants that,
among other things, “in [the Administrator’s] judgment, cause
or contribute to air pollution which may reasonably be
anticipated to endanger public health or welfare.” Id. §
7408(a)(1)(A). Once pollutants go on this list, the Administrator
must set national ambient air quality standards (NAAQS) for
them, i.e., ambient air concentration levels that, in the
Administrator’s judgment, “are requisite to protect the public
health” and in some areas are “requisite to protect the public
welfare.” Id. § 7409(b); see also id. §§ 7407, 7410(a)(1). States
must submit plans explaining how they will achieve these
NAAQS. Id. § 7410. According to EPA, these provisions
would be unworkable if applied to CO2: because CO2 disperses
relatively evenly throughout the lower atmosphere, states would
have only minimal control over their atmospheric CO2
concentrations and thus over whether they meet the CO2
NAAQS. EPA then concludes that because CO2 regulation
would be unworkable in the NAAQS context, no general CAA
provisions, including section 202(a)(1), authorize it to regulate
any GHGs.
    This unwieldy argument fails. Even assuming that states’
                                17

limited ability to meet CO2 NAAQS renders these provisions
unworkable as to CO2, but see id. § 7509a(a) (providing a safe
harbor for states that fail to meet NAAQS due to emissions
emanating from outside the country), the absurd-results canon
would justify at most an exception limited to the particular
unworkable provision, i.e., the NAAQS provision. See Mova
Pharm. Corp. v. Shalala, 140 F.3d 1060, 1068 (D.C. Cir. 1998).
As EPA acknowledges, regulating CO2 emissions from
automobiles is perfectly feasible. See 68 Fed. Reg. at 52,929
(noting that “improving fuel economy” is a “practical way of
reducing tailpipe CO2 emissions” and that other technologies for
reducing emissions may develop in the future).
     In support of its third justification for abandoning the plain
text of sections 202(a)(1) and 302(g), EPA relies on later
congressional action (and inaction). Specifically, EPA points
out (1) that all direct references to CO2 or global warming in the
1990 CAA amendments appear in nonregulatory provisions; (2)
that other congressional acts such as the 1978 National Climate
Program Act, the 1987 Global Climate Protection Act, the 1990
Global Change Research Act, and the 1992 Energy Policy Act,
as well as several appropriations riders, touch specifically on the
issue of global warming, typically by instructing agencies to
study the issue; and (3) that Congress has considered and
rejected many bills specifically tailored to GHG emissions
regulation since at least 1990. One might well wonder what all
this has to do with whether GHGs are “air pollutants” within the
meaning of CAA section 302(g). But relying almost exclusively
on Brown & Williamson, 529 U.S. 120, EPA claims that
together these facts indicate that the CAA’s general provisions
do not cover GHGs. EPA also asserts that, as in Brown &
Williamson, the “extraordinary” political and economic
significance of the regulation requested casts doubt on the
agency’s authority to undertake it. See Resp’t Br. at 21-22.
    In Brown & Williamson, the Court considered whether the
                                18

FDA had authority to regulate tobacco products. Although the
Food, Drug, and Cosmetic Act’s broad language suggested that
it did, the Court, acknowledging that “a specific policy
embodied in a later federal statute should control our
construction of the [earlier] statute, even though it ha[s] not been
expressly amended,” 529 U.S. at 143 (quoting United States v.
Estate of Romani, 523 U.S. 517, 530-31 (1998)) (alterations in
original), concluded that the FDA lacked such authority. In
reaching this conclusion, the Court relied on a direct,
irreconcilable conflict between FDA jurisdiction over tobacco
under the FDCA and later statutes expressly regulating tobacco.
If the FDA had jurisdiction over tobacco products, it would have
had to ban them entirely due to their health risks, yet the
subsequent acts “reveal[ed Congress’s] intent that tobacco
products remain on the market.” 529 U.S. at 139. Moreover, as
the Court emphasized—at least eighteen times by my
count—the FDA had repeatedly claimed to have “no authority
under the FDCA to regulate tobacco products,” id. at 157, and
“Congress’s tobacco-specific statutes ha[d] effectively ratified
the FDA’s long-held position,” id. at 144. See generally id. at
125-26, 130-31, 144-46, 151-57.
     EPA’s reliance on Brown & Williamson is misplaced. To
begin with, I am unconvinced by EPA’s contention that its
jurisdiction over GHG emissions would be as significant as
FDA jurisdiction over tobacco. Acting under the CAA, EPA
already extensively regulates the energy and transportation
industries, whereas the FDA had no prior authority over the
tobacco industry. Moreover, EPA jurisdiction would lead only
to regulation of GHGs—with, in the case of section 202,
regulation taking effect only after “such period as the
Administrator finds necessary” for development of technology,
“giving appropriate consideration to the cost of compliance,” 42
U.S.C. § 7521(a)(2). By contrast, FDA jurisdiction over tobacco
would have triggered a total product ban. But even assuming
the implications are equally significant, this is not an
                               19

“extraordinary” case where “common sense,” see Brown &
Williamson, 529 U.S. at 133, 159, calls into question whether
Congress has delegated EPA authority to regulate GHGs.
Congress gave EPA broad authority to regulate all harmful
pollutants, as section 202(a)(1)’s text makes clear. Congress did
so intentionally, deeming it “not appropriate to exempt certain
pollutants” from the Act’s “comprehensive protections.” See
H.R. Rep. No. 95-294, at 42-43. And, as I explain below, no
subsequent statutory indicia comparable to those relied on by the
Court in Brown & Williamson justify a different conclusion.
     Perhaps most significantly, no conflict exists between
EPA’s section 202(a)(1) authority to regulate GHGs and
subsequent global warming legislation. Whereas an FDA ban
on tobacco would have directly conflicted with congressional
intent that tobacco remain on the market, EPA regulation of
GHGs would be fully compatible with statutes proposing
additional research and other nonregulatory approaches to
climate change. Take the three 1990 CAA additions referencing
carbon dioxide or global warming. Section 103(g) calls for
“nonregulatory strategies and technologies” for reducing
pollutants like sulpher oxides, carbon monoxide, and carbon
dioxide. 42 U.S.C. § 7403(g). While the section also provides
that “[n]othing in this subsection shall be construed to authorize
the imposition on any person of air pollution control
requirements,” id. (emphasis added), it nowhere suggests that
EPA lacks authority to regulate carbon dioxide—or, for that
matter, sulpher oxides, carbon monoxide, and other
pollutants—under different parts of the Act. Section 602(e) is
similar. One sentence requires the Administrator to “publish the
global warming potential” of certain listed substances, and the
next sentence notes that “[t]he preceding sentence shall not be
construed to be the basis of any additional regulation under this
chapter.” Id. § 7671a(e). Once again, nothing in this provision
bars regulation under other parts of the Act. The third
provision—an uncodified section—merely requires sources
                                20

subject to the Act’s Title V to “monitor carbon dioxide
emissions,” and says nothing about regulation one way or the
other. Pub. L. No. 101-549, § 821, 104 Stat. 2399, 2699 (1990).
Other climate-related acts similarly demonstrating congressional
intent that global climate issues receive study and attention are
likewise perfectly compatible with GHG regulation. See
generally National Climate Program Act of 1978, Pub. L. No.
95-367, 92 Stat. 601; Global Climate Protection Act of 1987,
Pub. L. No. 100-204, §§ 1101-1106, 101 Stat. 1331, 1407-09;
Global Change Research Act of 1990, Pub. L. No. 101-606, 104
Stat. 3096; Energy Policy Act of 1992, Pub. L. No. 102-486, 106
Stat. 2776.
     Furthermore, and unlike subsequent tobacco legislation that
“effectively ratified the FDA’s previous position,” Brown &
Williamson, 529 U.S. at 156, this subsequent global-warming-
related legislation passed without any assurance from EPA that
the agency lacked authority to regulate GHGs. Quite to the
contrary, at the time of the two appropriations riders relied on by
EPA, see, e.g., Pub. L. No. 105-276, 112 Stat. 2461, 2496
(1998) (barring use of funds for implementation of the Kyoto
Protocol), EPA was taking the position that it possessed general
authority to regulate GHG emissions under section 202(a)(1).
See Memorandum, J. Cannon to C. Browner (April 10, 1998).
Finally, the fact that later Congresses failed to pass bills
specifically tailored to regulating global warming hardly
provides a basis for inferring that earlier Congresses meant to
exclude climate-endangering pollutants from the coverage of the
CAA’s general provisions. Not only is “subsequent legislative
history . . . a ‘hazardous basis for inferring the intent of an
earlier’ Congress,” but it “is a particularly dangerous ground . .
. when it concerns, as it does here . . . proposal[s] that do[] not
become law.” Pension Benefit Guar. Corp. v. LTV Corp., 496
U.S. 633, 650 (1990) (citation omitted). Indeed, in interpreting
the scope of the FDA’s authority, the Brown & Williamson
Court itself expressly declined to rely on failed legislation. 529
                                21

U.S. at 155.
     EPA has one last argument, applicable to CO2 emissions
alone, for claiming it lacks the authority the language of sections
202(a)(1) and 302(g) expressly bestow upon it. According to
EPA, the only practical way to regulate CO2 emissions from
motor vehicles is to require increased fuel economy, since CO2
is a byproduct of fuel combustion and “[n]o technology
currently exists or is under development that can capture and
destroy or reduce” CO2 “emissions from motor vehicle
tailpipes.” 68 Fed. Reg. at 52,929. Such regulation, EPA
reasons, would overlap substantially with DOT’s authority under
the 1975 Energy Policy and Conservation Act (EPCA) to set
average fuel economy standards for certain classes of motor
vehicles. See Pub. L. No. 94-163, § 502, 89 Stat. 871, 902-07
(1975). Though recognizing that no direct conflict would occur
since both agencies would set minimum standards, EPA
concludes that “any EPA effort to set CO2 tailpipe emissions
under the CAA would either abrogate EPCA’s regime (if the
standards were effectively more stringent than the applicable
[DOT] standard) or be meaningless (if they were effectively less
stringent).” 68 Fed. Reg. at 52,929.
     EPA may well be correct that setting standards for fuel
economy (rather than for capturing tailpipe emissions)
represents its only currently practical option for regulating CO2
emissions. But cf. 42 U.S.C. § 7521(a)(2) (requiring section
202(a)(1) regulation to take effect only “after such period as the
Administrator finds necessary to permit the development and
application of the requisite technology”). But given that the two
regulatory regimes—one targeted at fuel conservation and the
other at pollution prevention—are overlapping, not
incompatible, there is no reason to assume that Congress
exempted CO2 from the meaning of “air pollutant” within the
CAA, particularly since section 103(g) explicitly calls CO2 an
“air pollutant.” Where two “statutes are ‘capable of co-
                               22

existence,’ it becomes the duty of this court ‘to regard each as
effective’—at least absent clear congressional intent to the
contrary.” FTC v. Ken Roberts Co., 276 F.3d 583, 593 (D.C.
Cir. 2001) (quoting Morton v. Mancari, 417 U.S. 535, 551
(1974)). Moreover, Congress acknowledged, and indeed
accepted, the possibility of regulatory overlap. Not only does
the current EPCA recognize the relevance of “the effect of other
motor vehicle standards of the Government on fuel economy,”
49 U.S.C. § 32902(f); see also EPCA, Pub. L. No. 94-163, §
502(e), 89 Stat. at 905, but in passing the 1977 CAA
amendments Congress emphasized that EPA regulation under
the CAA should go forward even where it overlaps with
responsibilities given to other agencies under other acts, see
H.R. Rep. No. 95-294, at 42-43 (explaining that Congress was
amending section 302(g) to broaden the meaning of “air
pollutants” and make clear that EPA has authority even over
pollutants already regulated by another agency). As the 1977
House Report explained, “the Clean Air Act is the
comprehensive vehicle for protection of the Nation’s health
from air pollution. In the committee’s view, it is not appropriate
to exempt certain pollutants or certain sources from the
comprehensive protections afforded by the Clean Air Act.” Id.
      In sum, GHGs plainly fall within the meaning of “air
pollutant” in section 302(g) and therefore in section 202(a)(1).
If “in [the Administrator’s] judgment” they “cause, or contribute
to, air pollution which may reasonably be anticipated to
endanger public health or welfare,” 42 U.S.C. § 7521(a)(1), then
EPA has authority—indeed, the obligation—to regulate their
emissions from motor vehicles.

                               IV.
    EPA’s second reason for refusing to act—what EPA’s
counsel termed “the fallback argument,” Tr. of Oral Arg. at
41—is that even if GHGs are air pollutants, the agency gave
                                23

appropriate reasons and acted within its discretion in denying
the petition for rulemaking. EPA stresses that our “arbitrary and
capricious” standard of review is particularly deferential in
reviewing an agency refusal to institute rulemaking. See Resp’t
Br. at 11-12; cf. Motor Vehicle Mfrs. Ass’n v. EPA, 768 F.2d
385, 389 n.6 (D.C. Cir. 1985) (observing that the CAA judicial
review provisions are identical to those in the APA). This is
certainly true, but this court must nonetheless “consider whether
the agency’s decisionmaking was reasoned,” and we will not
permit the agency to make “plain errors of law.” See Am. Horse
Protection Ass’n, Inc. v. Lyng, 812 F.2d 1, 5 (D.C. Cir. 1987)
(internal quotation marks omitted). Indeed, “the agency has the
heaviest of obligations to explain and expose every step of its
reasoning,” so that we can “exercis[e] our responsibility to
determine whether [its] decision is ‘arbitrary, capricious, an
abuse of discretion, or otherwise not in accordance with law.’”
See Am. Lung Ass’n v. EPA, 134 F.3d 388, 392-93 (D.C. Cir.
1998) (quoting 42 U.S.C. § 7607(d)(9)) (reviewing EPA’s denial
of a petition to revise a NAAQS).
     In my view, EPA has failed to satisfy this standard. Indeed,
reading the relevant sections of EPA’s petition denial—one
titled “No Mandatory Duty,” another “Different Policy
Approach,” and a third “Administration Global Climate Change
Policy,” see 68 Fed. Reg. at 52,929, 52,931—I find it difficult
even to grasp the basis for EPA’s action. In its brief, EPA
describes the petition denial as claiming that if the agency thinks
regulating GHGs is a bad idea, the Administrator has discretion
to withhold making a “judgment,” known as an “endangerment
finding,” that GHG emissions “cause, or contribute to, air
pollution which may reasonably be anticipated to endanger
public health or welfare,” see 42 U.S.C. § 7521(a)(1). Yet the
denial itself seems to rest more clearly (albeit still not clearly)
on a belief that even if the Administrator makes an
endangerment finding, that finding triggers no duty to set
emission standards. In the end, though, it makes no difference
                                 24

whether one or both rationales are genuinely given in the
petition denial or whether they instead amount to post hoc
rescue attempts. As I explain below, neither rationale is
acceptable in light of section 202(a)(1)’s mandate.

     EPA’s Discretion to Make an Endangerment Finding
    In the petition denial, EPA states:
    [T]he CAA provision authorizing regulation of motor
    vehicle emissions does not impose a mandatory duty on the
    Administrator to exercise her judgment. Instead, section
    202(a)(1) provides the Administrator with discretionary
    authority to address emissions . . . . While section 202(a)(1)
    uses the word ‘shall,’ it does not require the Administrator
    to act by a specified deadline and it conditions authority to
    act on a discretionary exercise of the Administrator’s
    judgment regarding whether motor vehicle emissions cause
    or contribute to air pollution that may reasonably be
    anticipated to endanger public health or welfare.
68 Fed. Reg. at 52,929. Expounding on this passage, EPA
argues in its brief that “[t]he ICTA Petition Denial reflects
EPA’s decision not to make any endangerment finding—either
affirmative or negative—under section 202(a)(1).” Resp’t Br.
at 62-63. In EPA’s view, “the Agency’s authority to make the
threshold finding is discretionary” and petitioners err in
suggesting that “if the statutory test for making the finding is
met, EPA has no choice but to set standards.” Id. at 57 (internal
quotation marks omitted).
     EPA’s brief also turns several policy concerns raised in
other portions of its petition denial into rationales for holding off
examining endangerment.           These concerns include the
following: (1) “there continue to be important uncertainties in
our understanding of the factors that may affect future climate
change and how it should be addressed”; (2) petitioners
                               25

identified no technologies for reducing CH4, N2O, and HFC
emissions, and technologies for reducing CO2 emissions either
overlap with DOT’s authority or require further development;
(3) regulation “would also result in an inefficient, piecemeal
approach to addressing the climate change issue,” as the “U.S.
motor vehicle fleet is one of many sources of GHG emissions
both here and abroad”; (4) “[u]nilateral EPA regulation of motor
vehicle GHG emissions could also weaken U.S. efforts to
persuade key developing countries to reduce the GHG intensity
of their economies”; and (5) “EPA disagrees with the regulatory
approach urged by petitioners,” instead preferring “a number of
nonregulatory approaches to reducing GHG emissions” in line
with “the President’s global climate change policy” of
“support[ing] vital global climate research and lay[ing] the
groundwork for future action by investing in science,
technology, and institutions.” See 68 Fed. Reg. at 52,929-33.
     EPA’s reasoning is simply wrong. In effect, EPA has
transformed the limited discretion given to the Administrator
under section 202—the discretion to determine whether or not
an air pollutant causes or contributes to pollution which may
reasonably be anticipated to endanger public health or
welfare—into the discretion to withhold regulation because it
thinks such regulation bad policy. But Congress did not give
EPA this broader authority, and the agency may not usurp it.
     Section 202(a)(1)’s language—the “Administrator shall by
regulation prescribe . . . standards applicable to the emission of
any air pollutant from . . . new motor vehicles . . . which in his
judgment cause, or contribute to, air pollution which may
reasonably be anticipated to endanger public health or welfare,”
42 U.S.C. § 7521(a)(1)—establishes the limits of EPA’s
discretion. This section gives the Administrator the discretion
only to “judg[e],” within the bounds of substantial evidence,
whether pollutants “cause, or contribute to, air pollution which
may reasonably be anticipated to endanger public health or
                               26

welfare.” If conflicting credible evidence exists, e.g., some
evidence suggesting that GHGs may reasonably be anticipated
to endanger welfare and other evidence suggesting the opposite,
then the Administrator has discretion in weighing this evidence.
If the facts are known but require no single conclusion as to
whether a pollutant “may reasonably be anticipated to endanger
public health or welfare”—such as in a case where there exists
a small-to-moderate risk that a pollutant will cause a small-to-
moderate amount of harm—then the Administrator has
discretion in assessing whether these facts amount to
endangerment. If the Administrator concludes based on
substantial evidence that more research is needed before he can
judge whether GHGs may reasonably be anticipated to endanger
welfare, then he has discretion to hold off making a finding.
     But section 202(a)(1) plainly limits the Administrator’s
discretion—his judgment—to determining whether the statutory
standard for endangerment has been met. The Administrator has
no discretion either to base that judgment on reasons unrelated
to this standard or to withhold judgment for such reasons. In
claiming otherwise, EPA not only ignores the statute’s language,
but also fails to reckon with this circuit’s related precedent.
     Our en banc decision in Natural Resources Defense
Council, Inc. v. EPA, 824 F.2d 1146 (D.C. Cir. 1987), makes
clear that the Administrator may only exercise “judgment” in
evaluating whether the statutory standard has been met. There,
considering a CAA provision authorizing the Administrator to
set emission standards “at the level which in his judgment
provides an ample margin of safety to protect the public health,”
42 U.S.C. § 7412(b)(1)(B) (1982) (quoted in 824 F.2d at 1147),
we held that the Administrator had to base his determination on
what level would “provide an ‘ample margin of safety.’” See
824 F.2d at 1164-65. We struck down his proposed standards
because he failed to ground them in the statute. See id. at 1163-
64 (“[T]he Administrator has made no finding with respect to
                                27

the effect of the chosen level of emissions on health. . . .
Nowhere in the decision did the Administrator state that the
1976 emission standards provide an ‘ample margin of safety.’”).
      Similarly, in Ethyl Corp. v. EPA, 541 F.2d 1 (D.C. Cir.
1976) (en banc), we considered whether EPA appropriately
linked its policy analysis to the statutory standard. That case
involved EPA’s decision to regulate leaded gasoline pursuant to
CAA section 211(c)(1)(A), 42 U.S.C. § 1857f-6c(1)(A) (1976),
currently codified as amended at 42 U.S.C. § 7545(c)(1)(A),
which at that time provided that the Administrator “may”
regulate fuel additives “if any emission products of such . . . fuel
additive[s] will endanger the public health or welfare.”
Determining that lead in gasoline presented “‘a significant risk
of harm’ to the public health,” 541 F.2d at 7, EPA regulated it.
Industry petitioners objected, claiming that the Administrator
needed “proof of actual harm rather than of ‘a significant risk of
harm.’” Id. at 12. Siding with EPA, we held that the agency
had discretion in determining what level of harm—or risk of
harm—constitutes endangerment. Id. We indicated that such
determinations involve policy issues, but—as Judge Randolph
neglects to mention, see op. of Randolph, J., at 13—these policy
issues all related to whether the statutory standard had been met,
i.e., to whether lead in gasoline endangered public health. See,
e.g., 541 F.2d at 24 (observing that “a determination of
endangerment to public health is necessarily a question of policy
that is to be based on an assessment of risks and that should not
be bound by either the procedural or the substantive rigor proper
for questions of fact”); id. at 26 (noting that “the statute accords
the regulator flexibility to assess risks and make essentially
legislative policy judgments”). Indeed, Ethyl makes quite clear
that the Administrator’s policy-based discretion is limited to the
terms of the statute. “All this is not to say that Congress left the
Administrator free to set policy on his own terms. To the
contrary, the policy guidelines are largely set, both in the
statutory term ‘will endanger’ and in the relationship of that
                               28

term to other sections of the Clean Air Act. These prescriptions
direct the Administrator’s actions.” Id. at 29; cf. Brown &
Williamson, 529 U.S. at 140 (noting that the FDA’s “judgment”
about how best to achieve public health goals is “no substitute
for the specific safety determinations required by the FDCA’s
various operative provisions”).
     In yet another case, Her Majesty the Queen in Right of
Ontario v. EPA, 912 F.2d 1525 (D.C. Cir. 1990), we held that
for EPA to decline to make an endangerment finding, it must
have a statutorily based reason for doing so. The CAA section
at issue provided that when the Administrator had “reason to
believe that any air pollutant or pollutants emitted in the United
States cause or contribute to air pollution which may reasonably
be anticipated to endanger public health or welfare in a foreign
country . . . , the Administrator shall give formal notice thereof
to the Governor of the State in which such emissions originate.”
Id. at 1527-28 (quoting 42 U.S.C. § 7415(a) (1982)) (omission
in original). Petitioners alleged that the Administrator acted
unreasonably in holding off making an endangerment finding as
to acid rain, which strong evidence (including informal EPA
statements) indicated was coming from the United States and
endangering Canadian welfare. Id. at 1529. We held that EPA
acted reasonably in postponing a formal endangerment finding
only because it gave a reasonable statutory basis for doing so.
Specifically, because EPA still lacked information as to which
states were causing the harmful acid rain, it would have been
“pointless” for the agency to make an endangerment finding
given the “specific [statutory] linkage between the
endangerment finding and the remedial procedures,” i.e.,
notifying offending states. Id. at 1533. “For this reason,” we
found EPA’s decision to postpone an endangerment finding
“both reasonable and consistent with the statute.” Id.
      In short, EPA may withhold an endangerment finding only
if it needs more information to determine whether the statutory
                               29

standard has been met. Similarly, for EPA to find no
endangerment (as Judge Randolph, going beyond the agency’s
own arguments, appears to claim happened here, see op. of
Randolph, J., at 13, 15), it must ground that conclusion in the
statutory standard and may not rely on unrelated policy
considerations.
     The statutory standard, moreover, is precautionary. At the
time we decided Ethyl, section 202(a)(1) and similar CAA
provisions either authorized or required the Administrator to act
on finding that emissions led to “air pollution which endangers
the public health or welfare.” See 42 U.S.C. § 1857f-1(a)(1)
(1976) (emphasis added). After Ethyl found that “the statutes
and common sense demand regulatory action to prevent harm,
even if the regulator is less than certain that harm is otherwise
inevitable,” Ethyl, 541 F.2d at 25 (emphasis added), the 1977
Congress not only approved of this conclusion, see H.R. Rep.
No. 95-294, at 49, but also wrote it into the CAA. Section
202(a)(1) (along with other provisions, see H.R. Rep. No. 95-
294, at 50) now requires regulation to precede certainty. It
requires regulation where, in the Administrator’s judgment,
emissions “contribute to air pollution which may reasonably be
anticipated to endanger public health or welfare.” 42 U.S.C. §
7521(a)(1) (emphasis added). As the House Report explained:
“In order to emphasize the precautionary or preventative
purpose of the act (and, therefore, the Administrator’s duty to
assess risks rather than wait for proof of actual harm), the
committee not only retained the concept of endangerment to
health; the committee also added the words ‘may reasonably be
anticipated to.’” H.R. Rep. No. 95-294, at 51 (emphasis added).
     Given this framework, it is obvious that none of EPA’s
proffered policy reasons justifies its refusal to find that GHG
emissions “contribute to air pollution which may reasonably be
anticipated to endanger public health or welfare.” Unlike in Her
Majesty the Queen, EPA’s proffered reasons for refusing to
                                30

make an endangerment finding have no connection to the
statutory standard. Instead, as in Natural Resources Defense
Council (where we found EPA to have acted arbitrarily and
capriciously), EPA has “ventured into a zone of impermissible
action” by “simply substitut[ing]” freestanding policy concerns
for the sort of evaluation required by the statute. See 824 F.2d
at 1163. A look at these policy concerns proves the point.
     First, EPA claims that global warming still has many
scientific uncertainties associated with it. See 68 Fed. Reg. at
52,930-31; see also op. of Randolph, J., at 11-13. In this regard,
EPA makes much of the NRC’s statements that a link between
human-caused atmospheric GHG concentration increases and
this past century’s warming “cannot be unequivocally
established”; that “a wide range of uncertainty” remains
“inherent in current model predictions” due to imprecise
variables like future emissions rates, climate sensitivity, and the
forcing effects of aerosols; and that “current estimate [sic] of the
magnitude of future warming should be regarded as tentative
and subject to future adjustments (either upward or downward).”
See 68 Fed. Reg. at 52,930 (quoting NRC Rep. at 1, 17); see
also op. of Randolph, J., at 11-13. But the CAA nowhere calls
for proof. It nowhere calls for “unequivocal” evidence. Instead,
it calls for the Administrator to determine whether GHGs
“contribute to air pollution which may reasonably be anticipated
to endanger” welfare. EPA never suggests that the uncertainties
identified by the NRC Report prevent it from determining that
GHGs “may reasonably be anticipated to endanger” welfare. In
other words, just as EPA failed in Natural Resources Defense
Council to explain its chosen emissions level in light of the
statutory standard, so the agency has failed here to explain its
refusal to find endangerment in light of the statutory standard.
     EPA’s silence on this point is telling. Indeed, looking at the
NRC Report as a whole, I doubt EPA could credibly conclude
that it needs more research to determine whether GHG-caused
                              31

global warming “may reasonably be anticipated to endanger”
welfare. Though not offering certainty, the report demonstrates
that matters are well within the “frontiers of scientific
knowledge,” see op. of Randolph, J., at 15 (quoting Envtl. Def.
Fund v. EPA, 598 F.2d 62, 82 (D.C. Cir. 1978)). The report also
indicates that the projected consequences of global warming are
serious.     Because neither EPA nor Judge Randolph
acknowledges, let alone evaluates, these projected effects, I
quote the NRC’s discussion of the “Consequences of Increased
Climate Change of Various Magnitudes” in its entirety.
         The U.S. National Assessment of Climate Change
    Impacts, augmented by a recent NRC report on climate and
    health, provides a basis for summarizing the potential
    consequences of climate change. The National Assessment
    directly addresses the importance of climate change of
    various magnitudes by considering climate scenarios from
    two well-regarded models (the Hadley model of the United
    Kingdom and the Canadian Climate Model). These two
    models have very different globally-averaged temperature
    increases (2.7 and 4.4º C (4.9 and 7.9º F), respectively) by
    the year 2100. A key conclusion from the National
    Assessment is that U.S. society is likely to be able to adapt
    to most of the climate change impacts on human systems,
    but these adaptations may come with substantial cost. The
    primary conclusions from these reports are summarized for
    agriculture and forestry, water, human health, and coastal
    regions.
         In the near term, agriculture and forestry are likely to
    benefit from CO2 fertilization effects and the increased
    water efficiency of many plants at higher atmospheric CO2
    concentrations. Many crop distributions will change, thus
    requiring significant regional adaptations. Given their
    resource base, the Assessment concludes that such changes
    will be costlier for small farmers than for large corporate
                           32

farms. However, the combination of the geographic and
climatic breadth of the United States, possibly augmented
by advances in genetics, increases the nation’s robustness
to climate change. These conclusions depend on the
climate scenario, with hotter and drier conditions increasing
the potential for declines in both agriculture and forestry.
In addition, the response of insects and plant diseases to
warming is poorly understood. On the regional scale and in
the longer term, there is much more uncertainty.
     Increased tendency towards drought, as projected by
some models, is an important concern in every region of the
United States even though it is unlikely to be realized
everywhere in the nation. Decreased snow pack and/or
earlier season melting are expected in response to warming
because the freeze line will be moving to higher elevations.
The western part of the nation is highly dependent on the
amount of snow pack and the timing of the runoff. The
noted increased rainfall rates have implications for
pollution run-off, flood control, and changes to plant and
animal habitat. Any significant climate change is likely to
result in increased costs because the nation’s investment in
water supply infrastructure is largely tuned to the current
climate.
     Health outcomes in response to climate change are the
subject of intense debate. Climate change has the potential
to influence the frequency and transmission of infectious
disease, alter heat- and cold-related mortality and
morbidity, and influence air and water quality. Climate
change is just one of the factors that influence the frequency
and transmission of infectious disease, and hence the
assessments view such changes as highly uncertain. This
said, changes in agents that transport infectious diseases
(e.g., mosquitoes, ticks, rodents) are likely to occur with
any significant change in precipitation and temperature.
                          33

Increases in mean temperatures are expected to result in
new record high temperatures and warm nights and an
increase in the number of warm days compared to the
present. Cold-related stress is likely to decline whereas
heat stress in major urban areas is projected to increase if
no adaptation occurs. The National Assessment ties
increases in adverse air quality to higher temperatures and
other air mass characteristics. However, much of the
United States appears to be protected against many different
adverse health outcomes related to climate change by a
strong public health system, relatively high levels of public
awareness, and a high standard of living. Children, the
elderly, and the poor are considered to be the most
vulnerable to adverse health outcomes. The understanding
of the relationships between weather/climate and human
health is in its infancy and therefore the health
consequences of climate change are poorly understood.
The costs, benefits, and availability of resources for
adaptation are also uncertain.
     Fifty-three percent of the U.S. population lives within
the coastal regions, along with billions of dollars in
associated infrastructure. Because of this, coastal areas are
more vulnerable to increases in severe weather and sea level
rise. Changes in storm frequency and intensity are one of
the more uncertain elements of future climate change
prediction. However, sea level rise increases the potential
damage to coastal regions even under conditions of current
storm intensities and can endanger coastal ecosystems if
human systems or other barriers limit the opportunities for
migration.
    In contrast to human systems, the U.S. National
Assessment makes a strong case that ecosystems are the
most vulnerable to the projected rate and magnitude of
climate change, in part because the available adaptation
                              34

    options are very limited. Significant climate change will
    cause disruption to many U.S. ecosystems, including
    wetlands, forests, grasslands, rivers, and lakes. Ecosystems
    have inherent value, and also supply the country with a
    wide variety of ecosystem services.
         The impacts of these climate changes will be
    significant, but their nature and intensity will depend
    strongly on the region and timing of the occurrence. At a
    national level, the direct economic impacts are likely to be
    modest. However, on a regional basis the level and extent
    of both beneficial and harmful impacts will grow. Some
    economic sectors may be transformed substantially and
    there may be significant regional transitions associated with
    shifts in agriculture and forestry. Increasingly, climate
    change impacts will have to be placed in the context of
    other stresses associated with land use and a wide variety of
    pollutants. The possibility of abrupt or unexpected changes
    could pose greater challenges for adaptation.
         Even the mid-range scenarios considered in the IPCC
    result in temperatures that continue to increase well beyond
    the end of this century, suggesting that assessments that
    examine only the next 100 years may well underestimate
    the magnitude of the eventual impacts. For example a
    sustained and progressive drying of the land surface, if it
    occurred, would eventually lead to desertification of regions
    that are now marginally arable, and any substantial melting
    or breaking up of the Greenland and Antarctic ice caps
    could cause widespread coastal inundation.
NRC Rep. at 19-20 (footnotes omitted). I have grave difficulty
seeing how EPA, while treating the NRC Report as an
“objective and independent assessment of the relevant science,”
68 Fed. Reg. at 52,930, could possibly fail to conclude that
global warming “may reasonably be anticipated to endanger
public health or welfare,” 42 U.S.C. § 7521(a)(1), with effects
                               35

on welfare including “effects on soil, water, crops, vegetation,
manmade materials, animals, wildlife, weather, visibility, and
climate, damage to and deterioration of property, and hazards to
transportation, as well as effects on economic values and on
personal comfort and well-being,” id. § 7602(h). It thus comes
as no surprise that EPA’s petition denial not only undertakes
none of the risk assessments described in Ethyl, 541 F.2d at 28
& n.58, but also utterly ignores the statutory standard.
     EPA similarly fails to link its second policy
justification—that setting fuel economy standards represents the
only currently available way to regulate CO2 emissions and
petitioners “make no suggestion[s]” for how to reduce CH4,
N2O, and HFC emissions, 68 Fed. Reg. at 52,931—with the
statutory standard. As discussed earlier, supra at 21-22, the fact
that DOT sets fuel economy standards pursuant to the EPCA in
no way prevents EPA from setting standards pursuant to the
CAA. It is true that DOT has recently increased fuel economy
standards for light trucks, see 68 Fed. Reg. at 52,931; see also
op. of Randolph, J., at 14—a fact EPA did not even bother to
mention in its brief—but unless DOT’s action affects whether
GHGs “contribute to air pollution which may reasonably be
anticipated to endanger public health or welfare,” it provides no
support for EPA’s decision.
    As to EPA’s point about other GHGs, it may well be that no
current technologies exist for reducing their emissions. But
once again, this has nothing at all to do with the statutory
endangerment standard. Indeed, in section 202(a)(2), Congress
has made it crystal clear that endangerment findings must not
wait on technology.
    Any regulation prescribed under paragraph (1) of this
    subsection (and any revision thereof) shall take effect after
    such period as the Administrator finds necessary to permit
    the development and application of the requisite
                               36

    technology, giving appropriate consideration to the cost of
    compliance within such period.
42 U.S.C. § 7521(a)(2). As the Senate Report explained, EPA
“is expected to press for the development and application of
improved technology rather than be limited by that which
exists.” S. Rep. No. 91-1196, at 24 (1970); see also Natural
Res. Def. Council, Inc. v. EPA, 655 F.2d 318, 328 (D.C. Cir.
1981) (referencing this legislative history). In refusing to make
an endangerment finding because it lacks currently available
technology for controlling these emissions, EPA goes well
beyond the bounds of its statutory discretion.
     EPA’s final policy reasons likewise fail. Because other
domestic and foreign sources contribute to atmospheric GHG
concentrations, GHG regulation might well “result in an
inefficient, piecemeal approach to addressing the climate change
issue,” 68 Fed. Reg. at 52,931. But again, Congress has
expressly demanded such an approach. Section 202(a)(1)
requires EPA to regulate if it judges that U.S. motor vehicle
emissions “cause, or contribute to, air pollution,” 42 U.S.C. §
7521(a)(1) (emphasis added); see also Ethyl, 541 F.2d at 29-31
(holding that the same language from section 211 plainly means
that emissions merit regulation even if they are not the only
source of air pollution). EPA (understandably) offers no basis
for thinking that U.S. automobile emissions are not contributing
to global warming. Indeed, why would the “Administration’s
global climate change policy plan support[] increasing
automobile fuel economy,” see 68 Fed. Reg. at 52,933, if motor
vehicle emissions were contributing nothing to global warming?
Similarly, EPA’s concern that regulation could weaken U.S.
negotiating power with other nations has nothing at all to do
with whether GHGs contribute to welfare-endangering air
pollution. Finally, while EPA obviously prefers nonregulatory
approaches to regulatory ones, see id. at 52,932-33, Congress
gave the Administrator discretion only in assessing whether
                               37

global warming “may reasonably be anticipated to endanger”
welfare, not “free[dom] to set policy on his own terms,” Ethyl,
541 F.2d at 29.
     In short, EPA has utterly failed to relate its policy reasons
to section 202(a)(1)’s standard. Indeed, nowhere in its policy
discussion does EPA so much as mention this standard—“may
reasonably be anticipated to endanger public health or welfare.”
See 68 Fed. Reg. at 52,929-33 (the sections titled “Different
Policy Approach” and “Administration Global Climate Change
Policy”). EPA apparently dislikes the fact that section 202(a)(1)
says the Administrator “shall” regulate—rather than “may”
regulate—on making an endangerment finding. But EPA cannot
duck Congress’s express directive by declining to evaluate
endangerment on the basis of policy reasons unrelated to the
statutory standard. Although EPA is free to take its policy
concerns to Congress and seek a change in the Clean Air Act, it
must obey the law in the meantime.

  EPA’s Discretion After Making an Endangerment Finding
    Alternatively, EPA may have believed that even if it made
an endangerment finding, it had no obligation to regulate GHG
emissions. The petition denial states,
    EPA also disagrees with the premise of the petitioners’
    claim—that if the Administrator were to find that GHGs, in
    general, may reasonably be anticipated to endanger public
    health or welfare, she must necessarily regulate GHG
    emissions from motor vehicles. Depending on the
    particular problem, motor vehicles may contribute more or
    less or not at all. An important issue before the
    Administrator is whether, given motor vehicles’ relative
    contribution to a problem, it makes sense to regulate them.
    . . . The discretionary nature of the Administrator’s section
    202(a)(1) authority allows her to consider these important
    policy issues and decide to regulate motor vehicle
                               38

    emissions as appropriate to the air pollution problem being
    addressed. Accordingly, even were the Administrator to
    make a formal finding regarding the potential health and
    welfare effects of GHGs in general, section 202(a)(1) would
    not require her to regulate GHG emission from motor
    vehicles.
68 Fed. Reg. at 52,929. This passage is puzzling. Motor
vehicles emit GHGs in significant quantities, see U.S. Dep’t of
State, U.S. Climate Action Report 2002, at 40—a point EPA
nowhere contests.        The statute clearly states that the
Administrator “shall by regulation prescribe . . . standards”
governing the emissions of air pollutants from motor vehicles if
the Administrator makes an endangerment finding regarding
these pollutants. 42 U.S.C. § 7521(a)(1) (emphasis added).
Compare id. § 7545(c)(1)(A) (using “may”). Refusing to
regulate following an endangerment finding would violate the
law. Indeed, EPA appears to have abandoned this argument. In
a (rare) concession to the Act’s text, EPA counsel acknowledged
at oral argument, “I don’t think that we would contest that if the
agency had made an endangerment finding, that then you would
have to give some significance to the term ‘shall’ in [section]
202(a).” Tr. of Oral Arg. at 44.

                               V.
      Although this case comes to us in the context of a highly
controversial question—global warming—it actually presents a
quite traditional legal issue: has the Environmental Protection
Agency complied with the Clean Air Act? For the reasons given
above, I believe that EPA has both misinterpreted the scope of
its statutory authority and failed to provide a statutorily based
justification for refusing to make an endangerment finding. I
would thus grant the petitions for review.
