be lightning discharges, and while NO is quickly washed out of the lower
atmosphere by rain, some of it may reach the stratosphere. Additional
amounts of NO are produced directly in the stratosphere by cosmic rays from
the sun and interstellar sources.

It is because of this catalytic role which nitric oxide plays in the
destruction of ozone that it is important to consider the effects of
high-yield nuclear explosions on the ozone layer. The nuclear fireball and
the air entrained within it are subjected to great heat, followed by
relatively rapid cooling. These conditions are ideal for the production of
tremendous amounts of NO from the air. It has been estimated that as much
as 5,000 tons of nitric oxide is produced for each megaton of nuclear
explosive power.

What would be the effects of nitric oxides driven into the stratosphere by
an all-out nuclear war, involving the detonation of 10,000 megatons of
explosive force in the northern hemisphere? According to the recent
National Academy of Sciences study, the nitric oxide produced by the
weapons could reduce the ozone levels in the northern hemisphere by as much
as 30 to 70 percent.

To begin with, a depleted ozone layer would reflect back to the earth's
surface less heat than would normally be the case, thus causing a drop in
temperature--perhaps enough to produce serious effects on agriculture.
Other changes, such as increased amounts of dust or different vegetation,
might subsequently reverse this drop in temperature--but on the other hand,
it might increase it.

Probably more important, life on earth has largely evolved within the
protective ozone shield and is presently adapted rather precisely to the