Document ID: ./input/supremecourt_opinions/opinions/06pdf/05-1120.pdf
Page Number: 13.0

Cite as:  549 U. S. ____ (2007) 

7 

Opinion of the Court 

house gas emissions have significantly accelerated climate
change;  and  that  the  IPCC’s  1995  report  warned  that
“carbon dioxide remains the most important contributor to
[man-made] forcing of climate change.”  Id., at 13 (internal
quotation  marks  omitted).    The  petition  further  alleged
that  climate  change  will  have  serious  adverse  effects  on
human health and the environment.  Id., at 22–35.  As to 
EPA’s  statutory  authority,  the  petition  observed  that  the 
agency itself had already confirmed that it had the power 
to regulate carbon dioxide.  See id., at 18, n. 21.  In 1998, 
Jonathan  Z.  Cannon,  then  EPA’s  General  Counsel,  pre-
pared  a  legal  opinion  concluding  that  “CO2  emissions  are 
within  the  scope  of  EPA’s  authority  to  regulate,”  even  as 
he  recognized  that  EPA  had  so  far  declined  to  exercise 
that  authority. 
Id.,  at  54  (memorandum  to  Carol  M. 
Browner,  Administrator  (Apr.  10,  1998)  (hereinafter  Can-
non  memorandum)).    Cannon’s  successor,  Gary  S.  Guzy,
reiterated  that  opinion  before  a  congressional  committee 
just  two  weeks  before  the  rulemaking  petition  was  filed.
See id., at 61. 

Fifteen  months  after  the  petition’s  submission,  EPA
requested public comment on “all the issues raised in [the] 
petition,”  adding  a  “particular”  request  for  comments  on
“any scientific, technical, legal, economic or other aspect of 
these  issues  that  may  be  relevant  to  EPA’s  consideration 
of  this  petition.”  66  Fed.  Reg.  7486,  7487  (2001).    EPA 
received  more  than  50,000  comments  over  the  next  five 
months.  See 68 Fed. Reg. 52924 (2003).

Before the close of the comment period, the White House
sought  “assistance  in  identifying  the  areas  in  the  science 
of climate change where there are the greatest certainties 
and  uncertainties”  from  the  National  Research  Council, 
asking for a response “as soon as possible.”  App. 213.  The 
result was a 2001 report titled Climate Change: An Analysis 
of Some Key Questions (NRC Report), which, drawing heav-
ily  on  the  1995  IPCC  report,  concluded  that  “[g]reenhouse