The Nuclear Winter (2 page)

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Southern Hemisphere would experience effects that, while less severe than

in the Northern Hemisphere, are nevertheless extremely ominous. The illusion with which some people in the Northern Hemisphere reassure themselves -- catching an Air New Zealand flight in a time of serious international crisis, or the like -- is now much less tenable, even on the

narrow issue of personal survival for those with the price of a ticket.

But what if nuclear wars can be contained, and much less than 5000

megatons is detonated? Perhaps the greatest surprise in our work was that

even small nuclear wars can have devastating climatic effects. We considered a war in which a mere 100 megatons were exploded, less than one

percent of the world arsenals, and only in low-yield airbursts over cities. This scenario, we found, would ignite thousands of fires, and the

smoke from these fires alone would be enough to generate an epoch of cold

and dark almost as severe as in the 5000 megaton case. The threshold for

what Richard Turco has called The Nuclear Winter is very low.

Could we have overlooked some important effect? The carrying of dust and

soot from the Northern to the Southern Hemisphere (as well as more local

atmospheric circulation) will certainly thin the clouds out over the Northern Hemisphere. But, in many cases, this thinning would be insufficient to render the climatic consequences tolerable -- and every time it got better in the Northern Hemisphere, it would get worse in the

Southern.

Our results have been carefully scrutinized by more than 100 scientists in

the United States, Europe and the Soviet Union. There are still arguments

on points of detail. But the overall conclusion seems to be agreed upon:

There are severe and previously unanticipated global consequences of nuclear war-subfreezing temperatures in a twilit radioactive gloom lasting

for months or longer.

Scientists initially underestimated the effects of fallout, were amazed that nuclear explosions in space disabled distant satellites, had no idea

that the fireballs from high-yield thermonuclear explosions could deplete

the ozone layer and missed altogether the possible climatic effects of nuclear dust and smoke. What else have we overlooked?

Nuclear war is a problem that can be treated only theoretically. It is not

amenable to experimentation. Conceivably, we have left something important

out of our analysis, and the effects are more modest than we calculate.

On

the other hand, it is also possible-and, from previous experience, even likely-that there are further adverse effects that no one has yet been wise enough to recognize. With billions of lives at stake, where does conservatism lie-in assuming that the results will be better than we calculate, or worse?

Many biologists, considering the nuclear winter that these calculations describe, believe they carry somber implications for life on Earth.

Many

species of plants and animals would become extinct. Vast numbers of surviving humans would starve to death. The delicate ecological relations

that bind together organisms on Earth in a fabric of mutual dependency would be torn, perhaps irreparably. There is little question that our global civilization would be destroyed. The human population would be reduced to prehistoric levels, or less. Life for any survivors would be extremely hard. And there seems to be a real possibility of the extinction

of the human species.

It is now almost 40 years since the invention of nuclear weapons. We have

not yet experienced a global thermonuclear war -- although on more than one occasion we have come tremulously close. I do not think our luck can

hold forever. Men and machines are fallible, as recent events remind us.

Fools and madmen do exist, and sometimes rise to power. Concentrating always on the near future, we have ignored the long-term consequences of

our actions. We have placed our civilization and our species in jeopardy.

Fortunately, it is not yet too late. We can safeguard the planetary civilization and the human family if we so choose. There is no more important or more urgent issue.

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