Future prospects - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 335

preset in their minds. Had they not done this, the spread in estimates of tempera-
ture rise would be much greater. Thus, they have imposed their preconceived
notions of expected temperature rise on the models to make them come out
''right''. In Section 11.2 we discuss an estimate of climate sensitivity based on
paleoclimatic data.
Unfortunately, the topic of global warming has to some extent degenerated
into a quasi-religious belief system. There are those on the left (alarmists) who
believe that the end of the world is at hand and, like Old Testament prophets,
warn the populace of impending climatological disaster. The IPCC required over
1,000 pages to describe all the supposed negative impacts of global warming in the
21st century. Extravagant claims have been proposed, most of which are unsub-
stantiated. In opposition to the alarmists are the naysayers, who dispute some or
many of these claims, sometimes with cogent arguments and data. However, the far
right cadre of naysayers (in addition to serious scientists) also includes creationists,
religious nuts of several varieties, and others with little concern about desecration
of the environment. At both ends of the spectrum, the matter seems to rest on
faith rather than facts, and even scientists seem to have lost objectivity in many
instances.
An important analysis of the effect of CO 2 on climate was made by Lindzen
(1997). Many aspects are covered in his paper, but only a brief report on some
parts is given here. He answered the question posed by the title of his paper
(''Can increasing carbon dioxide cause climate change?'') with tongue in cheek by
saying nothing is impossible. But the real question is ''By how much and is it
discernible?''.
Lindzen emphasized:

''Water vapor, the atmosphere's main greenhouse gas, decreases in density
rapidly with both height and latitude. Surface radiative cooling in the tropics,
which has the highest concentration of water vapor, is negligible. Heat from the
tropical surface is carried upward by cumulus convection and poleward by the
Hadley circulation and planetary-scale eddies to points where radiation can more
eciently transport the heat to space. Where radiation can more eciently carry
the heat depends on the radiative opacity and the motions themselves. In point of
fact, without knowing the dynamical heat fluxes, it is clear that one cannot even
calculate the mean temperature of the Earth. It is interesting, in this regard, to
look at model intercomparisons of meridional heat flux, and their comparison
with observationally based estimates . Such differences [are] roughly

equivalent to differences in vertical fluxes of about 25W/m 2 —much larger than
the 4W/m 2 change that a doubling of CO 2 is expected to produce.''

...

There are two points here: (1) the tropics lose heat by processes other than
radiation and (2) meridional heat transfer is much greater than putative CO 2
forcing.
As we discussed previously, the prevailing view amongst climatologists is that
global warming due to increased CO 2 is amplified by increased water vapor