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change might come, not from CO 2 -induced warming, but from scenar-
ios that could send the mercury the other way. Today, skeptics of global
warming often point to this early uncertainty as evidence of the climate
science community playing Chicken Little and claiming that the sky— or
the temperature— is falling based on insufficient or uncertain evidence.
These critics tend to use the decades-old story to suggest, despite a pro-
pensity of findings to the contrary in the years following, that even today
there is considerable debate over the cooling theory. In fact, there is not. In
rebuttal, some scientists and science journalists have gone out of their way
to expose the “myth” of a cooling consensus, arguing that comparatively
few scientists supported the 1970s cooling thesis and that the community
as a whole never subscribed to the theory. 3 Their chief complaint— that
global warming skeptics and deniers have willfully and invidiously misin-
terpreted this episode in the early history of climate science to serve their
own purposes— does hold up, for the most part, under scrutiny. Even so,
the story of the warming/cooling debate is more dynamic than either side
lets on.
In the early 1970s, climate scientists generally agreed that climatic
change could adversely affect the human environment, but their research
produced two conflicting scenarios. The first, espoused primarily by atmo-
spheric scientists working with advanced computer models, involved an
overall increase in global temperatures caused by increases in atmospheric
CO 2 and other greenhouse gases. The second, promoted largely by cli-
matologists and geologists working with both models and physical and
documentary evidence of past climatic shifts, described a relatively sudden
decrease in global temperatures caused by potential combinations of volca-
nic dust, industrial pollutants, land-use changes, long-term cycles of solar
radiation, and abrupt changes in the circulation of water in the oceans.
Divisions between atmospheric scientists and historical climatologists
were not hard and fast, however. Atmospheric models at different levels
of sophistication also sometimes disagreed, alternately predicting warm-
ing or cooling. CO 2 -induced warming remained the most likely scenario
throughout the 1960s and 1970s, but as late as 1975 the scientific community
had yet to definitively rule out the cooling problem.
Atmospheric scientists, whose models highlighted the warming effects
of atmospheric CO 2 , dominated the study of climate in the late 1960s and
early 1970s. As early as 1967, Sukiro Manabe and Richard Weatherald, both
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