Report Warns Pentagon of Perils of a Nuclear Winter

The soot, smoke and dust raised by a nuclear war would bring about “far more extensive” requirements for the care of survivors than current civil defense plans anticipate, the Pentagon’s nuclear war experts have been warned.

In an unreleased report prepared by a private consulting firm for the Defense Nuclear Agency, the Pentagon was told that “present plans for evacuation of the population from cities to rural areas would not necessarily enhance long-term prospects for survival.”

The 73-page report--believed to be the first independent study of the long-range policy implications of nuclear winter prepared for the Pentagon--was written by Palomar Corp. and was delivered to the Defense Department earlier this summer. It was made available to The Times by the Pentagon, under the Freedom of Information Act.

The document, which does not represent official Pentagon policy, was intended to explore the potential national security implications of nuclear winter--the projected phenomenon in which dirt and other minuscule debris after a nuclear explosion would form a spreading cloud that could obscure the sunlight and lower temperatures around the globe.

At the Federal Emergency Management Administration, which is responsible for national civil defense, spokesman Russ Clanahan acknowledged that the agency “has not gone into the long-range implications” of nuclear winter.

“We are still in the process of learning what we need to know,” he said.

In addition to expressing concerns about the effectiveness of civil defense planning in the face of the long-term, post-attack impact of nuclear winter, the report also raised questions about the impact that the phenomenon could have on strategic thinking, the targets chosen for nuclear weapons and the Reagan Administration’s “Star Wars” missile defense program.

“At present, in detailed attack planning, U.S. planners do not consider the smoke-and-dust-creating potentials of given target types or of the particular warheads to be detonated at specific altitudes over those targets,” said the report, which is based on a yearlong study.

It warned that:

--The nuclear winter risk could make a “decapitating attack” on U.S. or Soviet command centers more attractive than a strike aimed at an adversary’s missile forces, which would require a far greater number of warheads and therefore would be more likely to raise a dust and smoke cloud. Construction of centers that have a greater degree of protection against a direct strike could be required.

--Extensive clouds, or “atmospheric opacity,” in the upper atmosphere after an attack could limit damage assessments and “complicate attempts to control escalation and to terminate a nuclear war.”

First-Strike Deterrent

But the report also said that concerns about nuclear winter could add to the uncertainties faced by decision makers and perhaps reduce incentives to initiate a nuclear attack for fear that the military advantages of a first strike might be outweighed by the long-term impact of the atmospheric phenomenon after a nuclear escalation.

It suggests that smaller weapons carrying single, lower-yield warheads, rather than the massive 10-warhead MX missile, could prove more strategically useful because they would reduce the risk of nuclear winter.

Similarly, it pointed out that a strike from the Soviet Union’s 10-warhead SS-18s “might no longer be a credible threat in a crisis because both sides would know it could lead to a global nuclear winter.”

And it warns that the limited nuclear options that form part of the nation’s nuclear deterrent “may not remain credible if they could result in a severe nuclear winter that threatened the survival of the United States--even if no nuclear weapons exploded on U.S. territory.”

On the other hand, if only a very high level of nuclear weaponry could produce a nuclear winter, the phenomenon “may not be very significant” because a general nuclear war would produce such extensive immediate destruction that its long-range impact “would be of relatively little consequence for planning purposes,” the report said.

Atmospheric Interference

The Reagan Administration’s controversial missile defense program, formally known as the Strategic Defense Initiative, could also be affected by nuclear winter, the report said. It said that smoke and dust in the upper atmosphere could interfere with optical sensors and other guidance and target systems, thereby reducing the defense system’s effectiveness.

The report pointed out that destruction of incoming warheads by such a defense system could reduce the likelihood of nuclear winter by precluding nuclear explosions. On the other hand, it said, it could increase the likelihood of nuclear winter if the attacked nation launched a massive retaliation.

The Defense Nuclear Agency, for which the report was written, is the chief Pentagon office concerned with the effects of nuclear weapons. Information it develops is used by strategic planners and policy makers.

“The report does not reflect the official policy of the Department of Defense,” Sue Ladd, a spokeswoman for the agency, said. “However, we will consider this report as we do all other information which contributes to our understanding of nuclear effects.”

Several studies in recent years have developed the theory that a nuclear war could bring about an extended period of freezing temperatures, lowering temperatures by 75 to 100 degrees in July. Even a limited nuclear exchange could bring about a short period of freezing temperatures that could ruin crops for an entire season, these studies found.

Many Uncertain Factors

Uncertainties about the nuclear winter phenomenon abound, however, and the impact would depend on the area hit by nuclear weapons, the amount of smoke and soot produced by the fires and the distribution and traveling speed of the cloud.

The nuclear winter, according to the scientific studies, would be caused when dust and millions of tons of smoke from burning cities would blacken the skies to such an extent that sunlight could not warm the land.

“Prospects for survival under these conditions might be greatly enhanced by advance civil defense planning and preparations,” the unreleased report said.

It noted: “The requirements for sheltering, feeding and otherwise caring for survivors of a nuclear conflict faced with a nuclear winter would be far more extensive (but not impossible) than those anticipated under current civil defense assumptions.”

The report added:

“Evacuated survivors of the immediate blast, thermal and short-term fallout effects of nuclear weapons detonations would have to be protected against prolonged periods of cold, darkness and radiation. Sustaining these survivors for months, rather than a few days or weeks, as now envisioned, could require construction of extensive and elaborate shelters and stockpiling of far larger supplies of food, fuel and fresh water than current preparations anticipate.”