Giant Brains - Four Revolutions in the Earth Sciences - page 226

A Thing to Worry About
By the late-1950s, the U.S. Weather Bureau had emerged as the key climate-mod-
eling agency. The director of the bureau's modeling project, Joseph Smagorinsky
(1924-2005),extendedanarmacrossthePacificOceantohireayoungPh.D.from
Tokyo University named Syukuro Manabe (b. 1931). The Weather Bureau's mod-
eling section was renamed the Geophysical Fluid Dynamics Laboratory (GFDL).
In 1968 it moved to Princeton as part of the National Oceanographic and Atmo-
spheric Administration (NOAA). Smagorinsky continued to direct the laboratory
until his retirement in 1983. Manabe turned out to be an expert at modeling and
Smagorinsky equally adept at extracting funds from government officials to keep
his lab equipped with state-of-the-art computers.
The early GFDL model divided the atmosphere into nine levels. Its equations
described how CO 2 , ozone, and water vapor absorb infrared radiation and how the
air trades heat and water with rudimentary ice caps, land, and ocean surfaces. In
1967, the GFDL modelers Manabe and Richard Wetherald reported their first res-
ults. For doubled CO 2 , the model showed a temperature rise of “about 2.3°C.” Be-
cause their model incorporated atmospheric convection, their results did not pro-
duce the “self-amplifying effect” that had caused unrealistic runaway warming in
some earlier models. 3
The Manabe-Wetherald model made one especially important prediction. As
greenhouse gases build up in the atmosphere, they absorb more upgoing heat rays,
warming the Earth's surface. But the more radiation blocked in the lower layer of
atmosphere, the troposphere, the less the amount rising into the upper layer, the
stratosphere. Therefore global warming ought to cause the troposphere to warm
and the stratosphere to cool. Were the Sun the cause of global warming, both the
troposphere and the stratosphere would warm. The prediction of a warming tropo-
sphere but cooling stratosphere offered a key test of the reality of global warming
and the reliability of climate models. But it would be a while before scientists had
the data to apply the test.
The Manabe-Wetherald model was the first to include enough known variables
to seem realistic to climate scientists. In its way, it awakened them in the same way
as Rutherford's first age measurements, or the Tharp-Heezen map of the Atlantic
Floor, or the Bullard fit of the continents. Wallace Broecker captured the feeling
when he told the author Spencer Weart that Manabe and Wetherald's 1967 paper
“convinced me this was a thing to worry about.” 4 In 1975, Broecker would be the
first to use the term “global warming” in a scientific publication. 5