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than canceled out the warming effects of CO 2 . Combined with smoke and
dust from agricultural activities and volcanoes, industrial pollution might
not only overpower the warming effects of CO 2 ; it might create a cooling
sufficient, in the right conditions, to trigger another ice age. 6
Challenged by these alarming results, modelers at NASA's Goddard
Institute for Space Studies (GISS), the National Center for Atmospheric
Research (NCAR), and the Geophysical Fluid Dynamics Laboratory
(GFDL) redoubled their efforts to create models that could handle com-
plex variables in order to prove or disprove the new theory. They started
with one-dimensional models that described vertical columns of air inde-
pendent of the influences of seasonality and landscapes— models like the
one Rasool and Schneider had used to demonstrate the potential climatic
effects of industrial aerosols. 7 Working with an influx of observed and
measured data from the Global Atmospheric Research Program, model-
ers pushed their programs to incorporate new and different aspects of the
global climate system. With every improvement in resolution beyond the
static, one-dimensional models of the 1960s, new ideas cropped up about
what questions the model might help to answer. Atmospheric modelers like
Rasool, Schneider, Sukiro Manabe (GFDL), Joseph Smagorinsky (GFDL),
Warren Washington (NCAR), Akira Kasahara (NCAR), and James Han-
sen (GISS) worked to increase the capacity of their models to deal with
large- and medium-scale externalities and feedbacks from throughout the
system. With increasing computer power, they made remarkable gains.
These increasingly sophisticated computer models tended to reaffirm
atmospheric scientists' initial conclusions that increasing CO 2 , rather than
aerosols, represented the biggest threat to global climatic stability. In the
new models, airborne solids presented enormous complexity. They did not
all act to cool the earth. As some climatologists already knew, atmospheric
dust by itself both reflects and absorbs sunlight. It can also provide the
nuclei for the formation of a reflective cloud layer, which in turn, depend-
ing on the type of clouds, might reduce the solar radiation reaching the
earth's surface, producing a cooling effect.8 8 But the new models showed
that the height, duration, and geographical distribution of aerosols also
made a difference in what effect they had. Some aerosols contributed to
cooling, as Bryson, Schneider, and Rasool had originally predicted, but
others actually contributed to warming. 9 Schneider himself pointed out
that some calculations in his paper with Rasool did not stand up to more
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