How should the government respond to the new declaration by reputable biologists that the effect of nuclear war might be much more serious than originally envisioned? This week in Washington Sen. William Proxmire asked that question of two panels of distinguished scientists. New investigations, he noted , argue that nuclear war could threaten the human race and other species with extinction. The new speculations have not been proved, he noted. But they are threatening enough to name the gloomy picture ''nuclear winter.'' Proxmire charges, ''The government has so far mostly ignored the nuclear winter findings, although a few agencies have belatedly begun studies.'' So what should the government do, he asks, and how long should it take?
Dr. Donald Kennedy of Stanford University summarized the new findings: ''What our most thoughtful projections show is that a major nuclear exchange will produce, among its many plausible effects, the greatest biological and physical disruptions of this planet in its last 65 million years - a period more than 30 thousand times longer than the time that has elapsed since the birth of Christ, and more than 100 times the life span of our species so far. That assessment of prospective risk needs to form a background for anyone who bears responsibility for national security decisions, here and elsewhere.''
Many scientists have concluded that it is not possible to have a ''small'' nuclear war; that the nation that sets off the first explosion will automatically trigger replies; that the retaliatory process will cause global dust and soot storms. The results would be like the storms surrounding Mars and would alter climate, freeze oceans, and block sunlight.
Witnesses include distinguished experts such as Russian physicist Andrei Sakharov, Nobel Peace Prize winner, who wrote an eloquent open letter in Foreign Affairs a year ago. He wrote that a nuclear war, ''with a certain degree of probability, would cause man to be destroyed as a biological species and could even cause the annihilation of life on earth.''
The bombs that destroyed Hiroshima and Nagasaki are diminutive compared with what now exists. As one group says, that would be just a ''match'' to light the new kind of fire. A new weapon might yield 500 kilotons (or 0.5 megatons). That's enough to help start a Martian-type dust storm.
The explosive power of all US and Soviet warheads today totals around 13,000 megatons. In the new book ''World After Nuclear War: The Cold and the Dark,'' an observer says, ''The scientific discoveries described in this book may turn out, in a world lucky enough to continue its history, to have been the most important research findings in the long history of science.''
This week witnesses said the chief danger is not blast, concussion, or collapse of cities, but soot. Soot and smoke, they explained, would cut off sunlight, with temperatures falling to 5 degrees F. or lower, when seas would freeze and snow would fall for months.
Carl Sagan of Cornell University described the relative position of the United States and Soviet Union to be like two men standing in six inches of gasoline. Each has a match, one is six inches long, the other 12 inches. Is one country better off than the other?