Geoscience Reference
In-Depth Information
of the Joint Numerical Weather Prediction Unit focused specifically on
GCMs. They called the unit the General Circulation Research Section.
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GCMs rely on two main elements to describe the global atmosphere.
The first is called the dynamic core of the model, a framework of assump-
tions based on the physical properties of the atmosphere, as expressed
through a set of nonlinear partial differential equations for fluid dynamic
motion called the Navier-Stokes equations. The dynamic core of early
GCMs typically revolved around the flow of energy, which GCM develop-
ers in the late 1950s had begun to explore through models of how the earth
absorbed energy from the sun and reflected it back into space (energy bud-
get models) and models of vertical energy transfers within and between the
elements of the earth's atmosphere (radiative-convective models). Overlaid
on top of this dynamic core is a second element of a GCM, the so-called
model physics of all the other processes of the atmosphere, including the
movements of air masses and atmospheric gases that affect weather and
climate throughout the globe.
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In the late 1950s, GCMs had already begun
to provide very rough, low-resolution simulations of how the global atmo-
sphere worked.
GCMs were not just about weather or climate, of course; like every-
thing else in the early history of climate science, they were developed with
Cold War applications in mind. As with CO
2
monitoring, general circu-
lation modeling benefited greatly from the massive quantities of radio-
isotopes dumped into the atmosphere by nuclear weapons tests at known
times and places throughout the 1950s. General circulation modelers traced
radioactive CO
2
and other irradiated material through the atmosphere to
provide observational data for their models.
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Atmospheric models, in
turn, provided a way to predict the distribution of radiation and fallout,
as well as a method for detecting and even locating foreign nuclear testing
activity.
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The benefits of this kind of modeling for defense-related Cold
War intelligence were not lost on anyone.
masters of infinity
Embedded in the government-sponsored efforts to model the atmosphere
and forecast weather was an optimistic idea that if humans could better
understand atmospheric processes, they could learn to control them. In
1946, General Electric's Nobel Prize- winning chemist Irving Langmuir
