precipitation, and clouds is a major area of current re-search (see, e.g., Tegen et al., 1996; Miller and Tegen,1998).The most catastrophic effects of anthropogenic aero-sols in the atmosphere could be those resulting from anuclear exchange between the great powers. Explosion,fire, and wind might generate a great pall of smoke anddust in the atmosphere, which would make the worlddark and cold. It has been estimated that if the ex-change reached a level of several thousand megatons,a ‘nuclear winter’ would be as low as −15° to −25°C(Turco et al., 1983), although more recent simulationsby Schneider and Thompson (1988) suggest that someprevious estimates may have been exaggerated. Theysuggest that in the Northern Hemisphere maximumaverage land surface summertime temperature depres-sions might be of the order of 5–15°C. The concept isdiscussed by Cotton and Piehlke (1995, chapter 10).Fears were also expressed that as a result of thesevere smoke palls (Figure 7.8) generated by the GulfWar in 1991 there might be severe climate impacts.Studies have suggested that because most of the smokegenerated by the oil-well fires stayed in the lowertroposphere and only had a short residence time inthe air, the effects were local (some cooling) ratherthan global, and that the operation of the monsoonwas not affected to any significant degree (Browninget al., 1991; Bakan et al., 1991). Furthermore, in the event
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