Document ID: ./input/supremecourt_opinions/opinions/06pdf/05-1120.pdf
Page Number: 59.0

6 

MASSACHUSETTS v. EPA 

SCALIA, J., dissenting 

information  contained  in  a  2001  report  by  the  National
Research Council (NRC) entitled Climate Change Science:
An Analysis of Some Key Questions: 

“As  the  NRC  noted  in  its  report,  concentrations  of 
[greenhouse  gases  (GHGs)]  are  increasing  in  the  at-
mosphere  as  a  result  of  human  activities  (pp. 9–12). 
It also noted that ‘[a] diverse array of evidence points 
to  a  warming  of  global  surface  air  temperatures’  (p.
16).  The  report  goes  on  to  state,  however,  that
‘[b]ecause  of  the  large  and  still  uncertain  level  of
natural variability inherent in the climate record and 
the  uncertainties  in  the  time  histories  of  the  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  es-
tablished.  The  fact  that  the  magnitude  of  the  ob-
served  warming  is  large  in  comparison  to  natural
variability  as  simulated  in  climate  models  is  sugges-
tive of such a linkage, but it does not constitute proof 
of  one  because  the  model  simulations  could  be  defi-
cient  in  natural  variability  on  the  decadal  to  century 
time scale’ (p. 17).

“The  NRC  also  observed  that  ‘there  is  considerable 
uncertainty  in  current  understanding  of  how  the  cli-
mate system varies naturally and reacts to emissions 
of [GHGs] and aerosols’ (p. 1).  As a result of that un-
certainty, the NRC cautioned that ‘current estimate of 
the magnitude of future warming should be regarded
as tentative and subject to future adjustments (either 
upward  or  downward).’  Id.   It  further  advised  that 
‘[r]educing  the  wide  range  of  uncertainty  inherent  in 
current  model  predictions  of  global  climate  change
will  require  major  advances  in  understanding  and 
modeling  of  both  (1)  the  factors  that  determine  at-