Page 159 - James Rodger Fleming - Fixing the sky

flake or ice crystal falling into [a supercooled cloud] may suffice to start a sudden
congelation, just as we see ice needles dart in all directions when a chilled sur-
face of a still pond is disturbed.” Speaking of towering convective clouds—which
are certainly large but not quiescent like a pond—McAdie noted, “We liken this
monstrous cloud to a huge gun, loaded and quiet, but with a trigger so delicately
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set that a falling snowflake would discharge it.” He predicted that “successful
rain engineers will come in time . . . from the ranks of those who study and clearly
understand the physical processes of cloud formation” (77). The key word here is
“trigger,” which is just what the General Electric scientists were attempting to do
in 1946.
Readers of the September 1930 issue of Popular Mechanics learned that a
Dutch scientist, August Veraart, had recently “succeeded” in producing rain
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by throwing dry ice power (solid Co ) on clouds. Veraart also claimed to be
2
able to produce more sunshine by conducting his seeding in the early morning,
which cleared the sky of fog, mist, and clouds for the rest of the day. From a small
airplane flying above the Zuider Zee, Veraart scattered some 3,300 pounds of
o
o
crushed ice particles cooled to a temperature of –78 C (–108 F) into growing
cumulus clouds. observers testified that the intervention was followed by falling
streaks of rain, although there is no evidence that the rain actually reached the
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ground. In 1931 Veraart published a small popular book in Dutch, now quite
rare, titled More Sunshine in the Cloudy North, More Rain in the Tropics. Here he
presented a history of his involvement in rainmaking, an overview of his experi-
ments and theories, and a summary of his wide, sweeping claims. 16
over the years, Veraart said, he had tried an assortment of seeding techniques
involving dry ice, supercooled water-ice, and ammonium salts. He theorized
that seeding particles could upset the stability or release instability in clouds,
release latent heat of condensation, and perhaps influence their electrical charges
to either dissolve them or condense their moisture into rain. As a kind of bud-
ding climate engineer, he speculated that the widespread application of such
techniques could produce both more rain (at night) and more sunshine, while
serving to purify the air and reduce the frequency and severity of storms. Veraart
thought that this would make the world better by rearranging climate zones that
were either too hot, too cold, too wet, or too dry.
Veraart died in 1932, before Bergeron and Findeisen published their work
on cloud physics. Meteorologists have minimized Veraart’s contribution, even
though he was using the “right” substance, by claiming that he probably did not
understand the mechanism involved in the precipitation process he triggered,
he did not realize that the dry ice was effective in development of ice crystals

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