Nuclear Winter Modeling A Sketch

To follow solar and thermal radiations through a smoke-and dust-laden atmosphere, TTAPS had used a height-resolved (one-dimensional; 1-D) radiative-convective model (RCM) with annual mean insolation. An RCM describes these processes in greater detail than general circulation models (GCMs) do but misses their horizontal motions. Further 1-D and 2-D studies, at the Lawrence Livermore National Laboratory (LLNL), the US National Aeronautics and Space Administration (NASA), and the University ofMaryland, helped clarifying basic effects and feedbacks including smoke uplift and changes in the snow-ice albedo, both of which may protract climatic effects. Like Covey, Schneider, and Thompson of the US National Center for Atmospheric Research (NCAR), who used a GCM of Australian origin with 7 atmospheric layers, Aleksandrov and Stenchikov of the Moscow Computing Center of the USSR Academy of Sciences (CCAS) confirmed TTAPS' major results. They used a coarse-resolution two-layer tropospheric GCM that had been adapted for different purposes in cooperation with Lawrence Gates of the Oregon State University (OSU), and equipped it with a simple ocean model. In addition to severe surface air temperature drops in continental interiors (mitigated near oceanic coasts) and large-scale thermal inversions of the atmosphere, clear signs of inter-hemispheric smoke transport due to a structural response of the Hadley circulation were noted by both groups.

These early 3-D 'nuclear winter' studies were admittedly quick shots: their immobile smoke stayed uninfluenced by atmospheric motions, did not interact with the hydrological cycle to become washed out, and could not buoyantly rise by solar heating. Though state-of-the-art in the early 1980s, artificial model climates had also to be left behind for more realistic assessments. Michael MacCracken and John Walton of the LLNL and the CCAS team introduced more realistic feedbacks into their two-layer GCMs, whereas the NCAR group focused on the model 'physics' first to keep firm footing. A visit in Moscow, coincidentally just before the 1983 Washington conference, triggered a study series by Stenchikov and Carl that addressed a 'minimum' disturbance (without minimizing the problem), traced conditions for Southern Hemisphere impacts, and explored the transient response for hints to answer the 1975 NAS question on 'postnuclear'

climate relaxation. This induced a closer view on the complexity of the acute phase of perturbation and its implications. Just during startup of this common work in Berlin, on 31 March 1985, Vladimir Aleksandrov vanished without a trace in Madrid. The shock and irritation about his disappearance and fate (which made him even an 'unperson' for a couple of months) drove the first of those studies into an unexpected tension field. Nevertheless, it helped to overcome the Soviet 'hard scenario' attitude and to tear down a barrier to public information at the German east side of the Iron Curtain.

The most detailed results were due to Thomas Malone and co-workers of the Los Alamos National Laboratory (LANL), who extended the NCAR GCM in the vertical to address the smoke transport more precisely. They confirmed the expected lofting into the lower stratosphere and thus a much prolonged residence and forcing. Though the NCAR authors fixed the important issue of 'quick freeze' beneath smoke clouds, notably in the subtropics and Tropics at startup of interhemispheric transport, a controversy arose from their inquiries suggesting change of the popular metaphor into 'nuclear fall'. Until 1987, persistent efforts to deblur longer-term effects due to the oceanic response have only been undertaken at the CCAS. In a more realistic atmosphere-ocean GCM study, virtually the last 'nuclear winter' publication for 15 years, Steve Ghan confirms Alan Robock's (1-D) finding that the acute-phase ocean and sea-ice response may bear climatic impacts for years.

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