Page 21 - James Rodger Fleming - Fixing the sky

that clearing the forests, draining the marshes, and cultivating the land would
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improve the American climate. In the 1840s, James Espy, the first meteorolo-
gist in U.S. government service, proposed rainmaking by lighting huge fires to
stimulate convective updrafts. The following era in rainmaking was dominated
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by artillerists and “rain fakers,” the so-called pluviculturalists. 6
Nineteenth-century climatologists could find no trends in the weather
records beyond variability and temporarily quashed the notion that humans can
influence climate. Yet by mid-century, geologists had discovered great changes,
ice ages and interglacial epochs, in the record of the rocks. The two timescales
(the human historical and the geological) and the two agencies (anthropogenic
forces and natural forces) were reunited in a new form at the dawn of the twenti-
eth century by the Swedish meteorologist Nils Gustaf Ekholm (1848–1923), who
wrote about “the climate of the geological and historical past.” Ekholm regarded
variations in carbon dioxide concentration as the principal cause of climatic vari-
ations, citing the “elaborate inquiry on this complicated phenomenon” made by
his colleague Svante Arrhenius. He explained that carbon dioxide is a key player
in the greenhouse effect and that this conclusion is based on the earlier work of
Joseph Fourier, John Tyndall, and others. By his estimates, an increase in car-
bon dioxide would heat high latitudes more than the tropics and would create
a warmer, more uniform climate over the entire Earth; a tripling of atmospheric

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carbon dioxide levels would raise global temperatures by 7to 9 C (12 to 16 F).
According to Ekholm, the secular cooling of the originally hot Earth was the
principal cause of variation in the quantity of carbon dioxide in the atmosphere.
As the Earth cooled, the oceans sequestered great amounts of carbon into lime-
stone and other calcium carbonate deposits, reducing the amount of carbon
dioxide in the air. This caused temperatures to fall, triggering a chain reaction
of feedback mechanisms that lowered carbon dioxide levels even further. other
processes added carbon dioxide to the air. Volcanic emissions, mountain uplift,
and changes in sea level and plant cover produced the periodical variations evi-
dent in the geological record.
Ekholm pointed out that humanity was now playing a role in these geologi-
cal processes. He held that over the course of a millennium the accumulation in
the atmosphere of Co from the burning of pit coal would “undoubtedly cause
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a very obvious rise of the mean temperature of the Earth.” He also thought this
effect could be accelerated by burning coal exposed in shallow seams or per-
haps decreased “by protecting the weathering layers of silicates from the influ-
ence of the air and by ruling the growth of plants.” Ekholm pointed to the grand
possibility that by such means it might someday be possible “to regulate the
future climate of the Earth and consequently prevent the arrival of a new Ice

4 | introduCtion