produce new and unexpected hazards. For example, we can assess
individually the consequences of heavy worldwide radiation fallout and
increased solar ultraviolet, but we do not know whether the two acting
together might significantly increase human, animal, or plant
susceptibility to disease. We can conclude that massive dust injection
into the stratosphere, even greater in scale than Krakatoa, is unlikely by
itself to produce significant climatic and environmental change, but we
cannot rule out interactions with other phenomena, such as ozone depletion,
which might produce utterly unexpected results.

We have come to realize that nuclear weapons can be as unpredictable as
they are deadly in their effects. Despite some 30 years of development and
study, there is still much that we do not know. This is particularly true
when we consider the global effects of a large-scale nuclear war.



Note 1: Nuclear Weapons Yield


The most widely used standard for measuring the power of nuclear weapons is
"yield," expressed as the quantity of chemical explosive (TNT) that would
produce the same energy release. The first atomic weapon which leveled
Hiroshima in 1945, had a yield of 13 kilotons; that is, the explosive power
of 13,000 tons of TNT. (The largest conventional bomb dropped in World War
II contained about 10 tons of TNT.)

Since Hiroshima, the yields or explosive power of nuclear weapons have
vastly increased. The world's largest nuclear detonation, set off in 1962
by the Soviet Union, had a yield of 58 megatons--equivalent to 58 million