When a modern thermonuclear device is exploded in the atmosphere, so much energy is released, so rapidly, that the normally inert atmospheric nitrogen combines with oxygen to produce quantities of oxides of nitrogen (NOx). The rapid heating of the air also sets up strong convection currents which carry the gases and other debris into the stratosphere, and it is there that most of the NOx is deposited. Since natural NOx is known to destroy ozone, it is only to be expected that the anthropogenically produced variety would have the same effect, and one of the many results of nuclear war might be the large scale destruction of the ozone layer. Most of the studies which originally investigated the effects of nuclear explosions on the atmosphere used data generated during the nuclear bomb tests of the 1950s and 1960s. After 1963, when a moratorium on atmospheric tests of nuclear devices was declared, information from these sources was no longer available, and recent investigations have been based on statistical models.
The results of the studies of the effects of nuclear-weapon tests on the ozone layer were not conclusive. The analysis of data collected during a period of intense testing in 1961 and 1962 produced no proof that the tests had had any effect on the ozone (Foley and Ruderman 1973), although it was estimated that the explosions should have been sufficient to cause a reduction of 3 per cent in stratospheric ozone levels (Crutzen 1974). Techniques for measuring ozone levels were not particularly sophisticated in the 1960s, and, in addition, a reduction of 3 per cent is well within the normal annual fluctuation in levels of atmospheric ozone. Thus, it was not possible to confirm or refute the predicted effects of nuclear explosions on the ozone layer by analysis of the test data. Circumstantial evidence did indicate a possible link, however. Since ozone levels are known to fluctuate in phase with sunspot cycles, it was expected that peak concentrations of ozone in 1941 and 1952 would be followed by a similar peak in 1963, in accordance with the eleven-year cycle. That did not happen. Instead, the minimum level reached in 1962 increased only gradually through the remainder of the decade (Crutzen 1974). The missing sunspot cycle peak was considered to be the result of the nuclear tests, and the gradual increase in ozone in the years following was interpreted as representing the recovery from the effects of the tests, as well as the return to the normal cyclical patterns (Hammond and Maugh 1974).
Although it was not possible to establish conclusive links between nuclear explosions and ozone depletion on the basis of these individual tests, a number of theoretical studies attempted to predict the impact of a full-scale nuclear war on stratospheric ozone. Hampson (1974) estimated that even a relatively minor nuclear conflict, involving the detonation of 50 megatonnes—equivalent to 50 million tonnes of conventional TNT explosive—would lead to a reduction in global ozone levels of about 20 per cent with a recovery period of several years. He pointed out the importance of thinking beyond the direct military casualties of a nuclear conflict to those who would suffer the consequences of a major thinning of the ozone layer. Since the destruction of the ozone layer would not remain localized, the effects would be felt worldwide, not just among the combatant nations. Subsequent studies by US military authorities at the Pentagon supported Hampson's predictions. They indicated that, following a major nuclear conflict 50-70 per cent of the ozone layer might be destroyed—with the greater depletion taking place in the northern hemisphere where most of the explosions would occur (Dotto and Schiff 1978).
Similar results were obtained by Crutzen (1974) using a photochemical-diffusion model. He calculated that the amount of nitric oxide injected into the stratosphere by a 500-megatonne conflict would be more than ten times the annual volume provided by natural processes. This was considered sufficient to reduce ozone levels in the northern hemisphere by 50 per cent. Dramatic as these values may appear, they remain approximations—based on data and analyses containing many inadequacies. Interest in the impact of nuclear war on the ozone layer peaked in the mid-1970s and declined thereafter. It emerged again a decade later as part of a larger package, dealing with nuclear war and climatology, which emphasized nuclear winter (see Chapter 5).
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Disasters: Why No ones Really 100 Safe. This is common knowledgethat disaster is everywhere. Its in the streets, its inside your campuses, and it can even be found inside your home. The question is not whether we are safe because no one is really THAT secure anymore but whether we can do something to lessen the odds of ever becoming a victim.