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The Baseline Nuclear Exchange The conclusions of any study of the consequences of nuclear war depend on the level and nature of the weapons exchange. The baseline case for this study, consistent with the mission statement, depicts a major nuclear war between the United States and the Soviet Union. The committee has not chosen the baseline assumptions to depict either the "most likely" general war scenario or the "worst-case. general war scenario. In defining the baseline case, the committee has sought to establish a credible, generalized account of the extent of a possible general nuclear war in the mid-1980s; hence it is not necessary to specify the manner in which this general war might begin or might escalate from the initial use of nuclear weapons or to designate specific weapons for specific targets. United States and Soviet nuclear forces reportedly now include about 50,000 nuclear weapons, with a total yield of some 13,000 Mt. About 25,000 of these nuclear weapons, with a yield of about 12,000 Mt. are on systems with strategic or major theater missions. The other 25,000 weapons, mostly of much smaller yield, are designed for tactical battlefield, air defense, antisubmarine, naval, and other special missions. In this analysis the committee has assumed (see Table 3.1) that approximately one-half of these weapons. or 25,000, would actually ~ _ _ This would include 12,500 strategic and major theater weapons with a yield of 6000 Mt and 12,500 tactical weapons with a yield of 500 Mt. The fraction of one-half has been applied to take into account the following factors that would reduce the number of weapons actually delivered on target: ~ _ , , be detonated, with a total Yield of about 6500 Mt. weapons destroyed by courter for ce attacks, weapons destroyed by defenses, weapon systems unreliable under combat conditions, and , _ _, _, _ ~ weapons held in reserve. This assumption should be within a factor of 2 of the exchange in a general nuclear war. The weapons in this exchange are all assumed to he 1 ~ ME Or lenn. with a major fraction less than 1.0 Mt. _ This represents a shift from many earlier analyses, which included significant numbers of 10- and 20-Mt bombs and missile warheads. -~ The elimination of very high yield weapons reflects the fact that both nations have, in recent years, been increasing the accuracy and fractionating the payloads of their missiles to obtain larger numbers of lower yield warheads. Similarly, multimegaton bombs have been replaced by more and smaller bombs and by 13

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14 TABLE 3.1 Baseline Case: Weapon Size Distribution Yield per Warhead (Mt) Number Total Yield (Mt) A. Total Detonated 1.5 220330 1.0 2,7002,700 0.75 330250 0.5 3,6001,800 0.25 2,400600 0.05 toO.153,200320 Tactical {misc.) 12,500 500 ~25,000 6,500 B. Ground Bursts 1.0 to 1.5 400 500 0.5 2,000 1,000 2,400 1,500 large numbers of stand-off cruise missiles with smaller yields. By 1985, there will probably be few, if any, multimegaton weapons deployed by either the United States or the Soviet Union, unless present trends are reversed. In a general nuclear war between the United States and the Soviet Union, the committee has assumed that all member nations of NATO and the Warsaw Pact would be involved and targeted for strategic weapons. The significance of this assumption to the study is that a number of targets located in urban areas, which are the major source of smoke, are found outside the United States and Soviet Union. It is further assumed that tactical nuclear war would for the most part be confined to the NATO/Warsaw Pact area (European Front) and the oceans. While other key allies and countries could well become involved in such a conflict, the committee did not have a specific military rationale for including targets in these nations. Moreover, modest numbers of military targets in such countries would not significantly alter the study results. The description of specific targets in all of these countries for 12,500 strategic and major theater weapons would be a difficult undertaking with no enduring validity. Even if the specific targeting plans of the nuclear powers were adopted, such detail could be misleading in suggesting that there would be a unique predictable pattern to a general nuclear exchange. Moreover, such detail is not relevant to this study, which relies on models that do not have as inputs the actual locations of targets. Factors such as proximity to oceans might be important to more sophisticated future models. The committee has assumed that each side would give highest priority to Counter force" attacks against the vulnerable components of

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15 the other side's threatening strategic forces and against the command, control, communications, and intelligence (C3I) facilities necessary to operate those forces effectively. It is also assumed that high priority would be given to destroying key military bases and transportation and communications nodes necessary for theater operations, particularly in Europe. The committee has assigned approximately 9000 effective warheads with a yield of some 5000 Mt to these missions. This would be consistent with each side's attacking each of the other side's strategic missile silos with two weapons in order to improve the kill probability; multiple attacks on several hundred military and civilian airfields capable of sustaining redeployed strategic aircraft; multiple attacks on submarine and naval bases; extensive attacks against the central civilian and military command and control systems, the critical nodes in the military communications system and facilities necessary to exploit intelligence assets for real-time targeting and damage assessment; and multiple attacks on several hundred major theater military targets. The committee has assumed that each side would, as a second priority, attack the other's economic base necessary to sustain its . .. .. . . .. . _ military efforts. These "countervalue" targets WOULD include plants producing military equipment, important components, and materials, petroleum refineries and storage, and electric power plants, as well as key transportation and communication nodes. In this scenario, some 3500 effective warheads with a yield of 1500 Mt would be used against such targets. While neither side would target population per se, the committee has assumed that neither would refrain from attacking urban areas if military or economic targets were located there. Most economic targets are co-located with urban areas, and many military targets, such as airfields capable of sustaining redeployed strategic aircraft, naval bases, and C I facilities, are also co-located with urban areas. The number of economic targets not co-located with urban areas may be comparable to the number of military targets that are co-located with urban areas. Therefore, for the purpose of this study the committee nas assumed that some ~5uu weapons wits a yield of approximately 1500 Mt would strike urban areas. Specifically, as a first approximation, it is assumed that economic targets and co-located military targets would be distributed in the largest 1000 NATO/Warsaw Pact urban areas roughly in proportion to the population of those areas. the chapter on fires resulting from such an attack, it is assumed that there would be one-third overlap of areas exposed to 20 cal/cm2. These assumptions imply that fire ignition would occur over 50 percent of the areas of these cities. The committee has assumed that both sides would fuze their warheads for air or ground burst to optimize military effectiveness against the targets under attack and not to increase population fatalities. With this in mind, it is estimated that about 25 percent (1500 Mt) of the total yield would be ground bursts. One ground burst is assumed against each silo and other hardened target. Given the large number and wide distribution of possible targets in this scenario, it is assumed as a first approximation that the targets As detailed in

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16 and megatonnage would be distributed evenly over the land areas from latitudes 30N to 70N. A more precise approximation of this distribution of megatonnage could be determined by examining the density of known major strategic targets and urban areas within these latitudes; however, such detail would not add appreciable precision to the present estimation of atmospheric consequences until knowledge about soot production, transport, and removal is much improved. It is important to note that this weapons exchange assumes that all targets would have been chosen to have direct or indirect impact on the ability of the two sides to conduct or sustain military operations or to emerge from the hostilities in a superior position. No targets would be chosen to maximize worldwide population fatalities or long-term effects on the biosphere. Consequently, it is assumed that there would be no attacks on urban areas in countries not directly involved in the conflict. The committee has assumed that there would be no attacks solely designed to ignite or sustain forest fires--and no attacks on oil fields, since the destruction of storage facilities and refineries would provide more immediate and effective denial of petroleum products. In addition, it is assumed that the war at sea would be directed against specific ships and submarines. In this 6500-Mt baseline case, no large multimegaton weapons would be employed by either side. In order to examine the atmospheric effects of very high yield explosions, the committee has also analyzed a second case--an 8500-Mt excursion--in which sufficient multimegaton (i.e., 20 Mt) missile warheads would be deployed to permit successful delivery of approximately 100 such weapons on superhard, high-value targets, in addition to the 6500-Mt baseline megatonnage. It is assumed that these would all be surface bursts.