active fallout from a nuclear war; an important aspect
of this new study was its inquiry into all possible consequences,
including the effects of large-scale nuclear detonations on the ozone
layer which helps protect life on earth from the sun's ultraviolet
radiations. Assuming a total detonation of 10,000 megatons--a
large-scale but less than total nuclear "exchange," as one would say in
the dehumanizing jargon of the strategists--it was concluded that as
much as 30-70 percent of the ozone might be eliminated from the
northern hemisphere (where a nuclear war would presumably take place)
and as much as 20-40 percent from the southern hemisphere. Recovery
would probably take about 3-10 years, but the Academy's study notes
that long term global changes cannot be completely ruled out.

The reduced ozone concentrations would have a number of consequences
outside the areas in which the detonations occurred. The Academy study
notes, for example, that the resultant increase in ultraviolet would
cause "prompt incapacitating cases of sunburn in the temperate zones
and snow blindness in northern countries . . ."

Strange though it might seem, the increased ultraviolet radiation could
also be accompanied by a drop in the average temperature. The size of
the change is open to question, but the largest changes would probably
occur at the higher latitudes, where crop production and ecological
balances are sensitively dependent on the number of frost-free days and
other factors related to average temperature. The Academy's study
concluded that ozone changes due to nuclear war might decrease global
surface temperatures by only negligible amounts or by as much as a few
degrees. To calibrate the significance of this, the study mentioned
that a cooling of even 1 degree centigrade would eliminate commercial
wheat growing in Canada.

Thus, the possibility of a serious increase in ultraviolet radiation
has been added to widespread radioactive fallout as a fearsome
consequence of the large-scale use of nuclear weapons. And it is
likely that we must reckon with still other complex and subtle
processes, global in scope, which could seriously threaten the health
of distant populations in the event of an all-out nuclear war.

Up to now, many of the important discoveries about nuclear weapon
effects have been made not through deliberate scientific inquiry but by
accident. And as the following historical examples show, there has been
a s