Geoscience Reference
In-Depth Information
and Starley Thompson at NCAR in the spring of 1983, with funding from
the Defense Nuclear Agency. In loose collaboration with the TTAPS group
and the Lawrence Livermore National Laboratory, the NCAR team sought
to create a more realistic picture of the climatic consequences of a nuclear
exchange by re-creating the TTAPS scenarios using a three-dimensional
climate model. Scientifically, the episode recalled Schneider's own paper
on aerosol cooling with Ishtiaque Rasool in the early 1970s. Whereas the
TTAPS study derived its conclusions from a model of a vertical column of
“dead air,” this time it was Schneider and his group who worked to incor-
porate seasonal variations, horizontal mixing, and the stabilizing force of
the oceans into their model.
Almost immediately, NCAR's results began to differ from the TTAPS
study. Qualitatively, the NCAR model supported the nuclear winter phe-
nomenon: in the event of a nuclear exchange, in all likelihood smoke, soot,
and dust would lead to a catastrophic cooling of large portions of the earth.
But the details of the three-dimensional model revealed a more complex
and somewhat less stark range of specific climatic responses. A nuclear war
in the summertime had nearly the same severity of consequences in both
the one-dimensional and three-dimensional models, but a January strike
in NCAR's model (a scenario impossible to simulate in the TTAPS model)
yielded much tamer impacts. In all of the three-dimensional scenarios, the
oceans significantly modulated the overall temperature change, especially
near the coasts, and ultimately the climatic result that Schneider and his
colleagues arrived at resembled the variability of a severe and unpredict-
able autumn more than a deep winter freeze. Perhaps most important, the
variability revealed by Schneider's three-dimensional model— the “real
world,” as he called it— seemed to undermine Sagan's “crude threshold”
for perpetual winter.
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Between the fall of 1983 and the summer of 1986, Sagan and Schneider
engaged in a series of exchanges on the issue. Initially, Schneider privately
tried to convince Sagan to back of of the threshold idea, which Schnei-
der believed to be an artifact of the one-dimensional model. Schneider
shared Sagan's general bent toward disarmament, and like Sagan he hoped
that the climatic effects of a nuclear exchange would help demonstrate the
insanity of the “winnable” nuclear war concept. An outspoken liberal who
had as early as 1977 encouraged Sagan to use his popular appeal to take
more of a political stand on scientific issues, Schneider certainly believed
