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complex models. 10 As modelers incorporated dimensions like variable
humidity, seasonality, and differences between tropospheric and strato-
spheric behavior, the increases in CO 2 attendant to fossil fuel consumption
appeared as a more powerful force than aerosols in affecting the overall
radiation budget of the globe. 11
Bryson and other climatologists still were not convinced; but by the late
1970s, warming seemed to many scientists the most likely climatic prob-
lem. As oceanographer Wally Broecker of Columbia University's Lamont-
Doherty Geological Observatory wrote in Science in 1975, “A strong case
can be made that the present cooling trend will, within a decade or so, give
way to a pronounced warming induced by carbon dioxide.” 12 By the late
1970s, Broecker's terminology had caught on, and global warming began to
enter both the scientific and popular lexicons. 13
Still, divisions persisted within the climate science community, and
these divisions tended to reflect differences over methodologies, which
varied between disciplines. Steeped in a tradition of measurement and
empiricism, more traditional meteorologists and climatologists like Bryson
and former Weather Bureau director of climatology Helmut Landsberg dis-
trusted the theoretical nature of general circulation models, which failed,
in their minds, to account for the observed conditions of the climatic past.
Historical meteorologists, geologists, and climatologists all worked with
computer models, but they preferred physical, documentary, and statistical
evidence of real past events, which gave them reference points for address-
ing the possible causes of a contemporary climatic shift.
General circulation modelers looking at CO 2 , though they disagreed
emphatically over how to structure models and what those models might
reveal, as a group retorted that the traditional standard of empiricism
had no place in theoretical constructions of future climates. The atmo-
spheric conditions of those climates— twice the atmospheric CO 2 in
this case— had no corollary in human history. Instead of relying on the
historical-statistical methods of geologists and other climatologists, gen-
eral circulation modelers set theoretically plausible boundary conditions
and then ran numerical simulations of atmospheric phenomena based on
the laws of fluid mechanics. These models described simplified interac-
tions between components of the atmosphere, including the dust and aero-
sols that so concerned Bryson.
The disciplinary divisions that shaped the warming/cooling debate
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