The unthinkable

A group of biologists and physicists have been in Washington this week considering the effect of nuclear war. They specifically banned polemics and politics: They just asked, ''What would probably happen?'' They were about as distinguished a group as you could find - Donald Kennedy, who spoke first, is president of Stanford University; Dr. Carl Sagan, who followed, is from Cornell, and there was a nucleus of about 40 of like stature. They considered ''The Long-Term Worldwide Biological Consequences of Nuclear War.'' What did they find? What would be the consequences? Why, to put it simply, it might drive civilization out of business.

As a newspaperman I write a lot about nuclear war and the confrontations of the United States and Russia. It is the dominant international topic of the day. All over Europe passionate arguments continue.

But this was different.

This conference persuaded me that there is a third party to all the disputes, what might be called the pro-Earth party.

It was impressive, listening to the uneditorialized and relatively calm comments. They even had a couple of Soviet scientists join the discussion by satellite. What did they find? Why, they all agreed (or seemed to): The potential now exists for destroying civilization on earth. It doesn't seem to be theoretical any more. Man can do it.

The biologists, the atmospheric scientists - all the others in the respective panels - were not just talking for forensic effect; they displayed scientific curiosity about the way it would turn out and kept personal emotions (or pretended to) out of the equations. They were trying to approach the matter with systematic study.

The postulate was that one country (or group) would first use the nuclear bomb and that somebody else would retaliate. That might destroy about half the human race, but how about the survivors and the rest of the planet? This group of research scientists picked it up from there. They were trying to bring an element of research into the UNTHINKABLE.

Things that happened in milliseconds, some concluded, would overturn the developments of millenniums. Here is Dr. Kennedy talking about it:

''I think it is fair to say that the most striking new information presented at this conference - and indeed the most potentially disturbing of all of the chronic effects of nuclear war so far described - is the prospect of major climatic consequences. Those consequences are so profound that they could dwarf all of the other long-range effects so far described.''

Who knows what would happen? The biologists lead us into a nightmare world. Has something like it happened before? After all, what happened to the dinosaurs? It is all frightening and controversial and sensational and, from the point of view of the journalists, one biological speculation is about as alarming as the next. The point that grows on the listener is that this isn't make-believe; it is what we must begin to think of as reality. The conference here was held in a luxurious hotel with overstuffed chairs, and we lolled around wondering about Earth's destruction.

The sharpest exchange I heard (and one where the rule against policy discussions momentarily slipped) occurred when somebody in the audience simply put a concrete question to a speaker: ''You mean that any country that exploded a bomb would be committing suicide?'' The answer was a simple unemotional ''Yes.''

Biologists and physicists have not communicated their conclusions to the world's leaders, to the generals and admirals who order the bombs exploded, or to the man in the street who listens to the football game on the Saturday broadcast.

The bombs do more than kill multitudes - that's horrifying enough. That might wipe out half of the human race. But after that - what? Low-keyed biologists answer that they also interfere with the ''ecological system.''

We are living in a paradox. Billions are going for nuclear weapons which, say these scientists, are as dangerous to the senders as to the victims.

''Even small nuclear wars can have devastating climatic effects,'' said Prof. Carl Sagan, ''enough to generate an epoch of cold and dark.''