It has now been two decades since the introduction of thermonuclear
fusion weapons into the military inventories of the great powers, and
more than a decade since the United States, Great Britain, and the
Soviet Union ceased to test nuclear weapons in the atmosphere. Today
our understanding of the technology of thermonuclear weapons seems
highly advanced, but our knowledge of the physical and biological
consequences of nuclear war is continuously evolving.
Only recently, new light was shed on the subject in a study which the
Arms Control and Disarmament Agency had asked the National Academy of
Sciences to undertake. Previous studies had tended to focus very
largely on radioactive 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 series of surprises.
"Castle/Bravo" was the largest nuclear weapon ever detonated by the
United States. Before it was set off at Bikini on February 28, 1954,
it was expected to explode with an energy equivalent of about 8 million
tons of TNT. Actually, it produced almost twice that explosive
power--equivalent to 15 million tons of TNT.
If the power of the bomb was unexpected, so were the after-effects.
About 6 hours after the explosion, a fine, sandy ash began to sprinkle
the Japanese fishing vessel Lucky Dragon, some 90 miles downwind of the
burst point, and Rongelap Atoll, 100 miles downwind. Though 40 to 50
miles away from the proscribed test area, the vessel's crew and the
islanders received heavy doses of radiation from the weapon's
"fallout"--the coral rock, soil, and other debris sucked up in the
fireball and made intensively radioactive by the nuclear reaction. One
radioactive isotope in the fallout, iodine-131, rapidly built up to
serious concentration in the thyroid glands of the victims,
particularly young Rongelapese children.
More than any other event in the decade of testing large nuclear
weapons in the atmosphere, Castle/Bravo's unexpected contamination of
7,000 square miles of the Pacific Ocean dramatically illustrated how
large-scale nuclear war could produce casualties on a colossal scale,
far beyond the local effects of blast and fire alone.
A number of other surprises were encountered during 30 years of nuclear
weapons development. For example, what was probably man's most
extensive modification of the global environment to date occurred in
September 1962, when a nuclear device was detonated 250 miles above
Johnson Island. The 1.4-megaton burst produced an artificial belt of
charged particles trapped in the earth's magnetic field. Though 98
percent of these particles were removed by natural processes after the
first year, traces could be detected 6 or 7 years later. A number of
satellites in low earth orbit at the time of the burst suffered severe
electronic damage resulting in malfunctions and early failure. It
became obvious that man now had the power to make long term changes in
his near-space environment.
Another unexpected effect of high-altitude bursts was the blackout of
high-frequency radio communications. Disruption of the ionosphere
(which reflects radio signals back to the earth) by nuclear bursts over
the Pacific has wiped out long-distance radio communications for hours
at distances of up to 600 miles from the burst point.
Yet another surprise was the discovery that electromagnetic pulses can
play havoc with electrical equipment itself, including some in command
systems that control the nuclear arms themselves.
Much of our knowledge was thus gained by chance--a fact which should
imbue us with humility as we contemplate the remaining uncertainties
(as well as the certainties) about nuclear warfare. What we have
learned enables us, nonetheless, to see more clearly. We know, for
instance, that some of the earlier speculations about the after-effects
of a global nuclear war were as far-fetched as they were
horrifying--such as the idea that the worldwide accumulation of
radioactive fallout would eliminate all life on the planet, or that it
might produce a train of monstrous genetic mutations in all living
things, making future life unrecognizable. And this accumulation of
knowledge which enables us to rule out the more fanciful possibilities
also allows us to reexamine, with some scientific rigor, other
phenomena which could seriously affect the global environment and the
populations of participant and nonparticipant countries alike.
This paper is an attempt to set in perspective some of the longer term
effects of nuclear war on the global environment, with emphasis on
areas and peoples distant from the actual targets of the weapons.