NUCLEAR WINTER: THE WAGES OF HYPE

  The ' Nuclear Winter ' Meltdown

THIS IS NOT A
CLIMATE MODEL:
COVER ART FROM THE
CREATIVE DEPARTMENT
OF PORTER NOVELLI
ARTIST JON LOMBORG
ALSO DESIGNED THE 
VOYAGER PROBE ICON

I  declined Retro TV producer  Kit Roan's kind invitation to add a few sound bites to his  what  happened  to  ' nuclear winter '?  episode, but a Times Op-ed from the true believers  that claims their parrot isn't stuffed reveals an historical symmetry worth exploring.

While Cold War efforts to scare the world into disarmament devolveded into a scientific fiasco- the melt down of  estimated  'nuclear winter'  impacts in the face of further research recalls the transformation of the 'Energy Crisis' into the 'Oil Glut', and  the implosion of "The Population Bomb."  'nuclear winter'  still deserves credit for surfacing the concept of radiative climate forcing, albeit by exaggerating it by several orders of magnitude or more.

Scientists at large may disdain media hype, but in consciousness raising, nothing succeeds like excess. Nuclear winter became as famous as Carl Sagan could make it on The Johnny Carson Show, a P-R tour de force Madison Avenue and K-Street have not forgotten, witness energy industry flacks adopting the peace movement's worst polemic excesses  as Best Practices in denying positive radiative forcing by CO2.

Roan asked for primary sources, so here are direct quotes, graphs, & articles from Foreign Affairs, The New Republic, The National Interest and Nature that  raise  some  interesting questions:

What drove the eminently liberal President of The Council for a Livable World to call the "nuclear winter " PR campaign:

              'The  worst example of  the misrepresentation of science

                                         to  the  public  in  my  memory.' ?

Why did the present Director of the Harvard Center for Climate and Security characterize the TTAPS 'nuclear winter ' manuscript as:

          "a political document rather than a scientific document "  

What  led  Science  senior  writer  Eliot Marshall  to call the  theory one of  the "great science fictions of the Reagan era" ?

Or  compelled Al Gore to tell a "Is Nuclear Winter Real and Relevant?" symposium that the apocalyptic hypothesis was 

            "too uncertain  to justify  changing  strategic doctrine"  ? 

And what did TTAPS authors -Turco, Toon, Ackerman, Pollack and Sagan, do that led Nobel laureate, Richard Feynman to conclude:

"You know, I really don't think these guys 

know what they're talking about."

The ruckus began in 1983 in Foreign Affairs, when Carl Sagan wrote :

"Apocalyptic predictions require, to be taken seriously, higher standards of evidence than do assertions on other matters where the stakes are not as great."

This presented a problem, for the extraordinary evidence for his extraordinary  (and very scary)  claims wasn't forthcoming,  and the process that gave rise to them was far from transparent.  In consequence, as  Nature  noted in  editorials at the height of the Cold War, and I repeated there in 2011:

Nuclear winter was and is debatable

Russell Seitz

Alan Robock's contention that there has been no real scientific debate about the 'nuclear winter' concept is itself debatable (Nature 473, 275–276; 2011).

This potential climate disaster, popularized in Science in 1983, rested on the output of a one-dimensional model that was later shown to overestimate the smoke a nuclear holocaust might engender. More refined estimates, combined with advanced three-dimensional models (see http://go.nature.com/kss8te), have dramatically reduced the extent and severity of the projected cooling.

Despite this, Carl Sagan, who co-authored the 1983 Science paper, went so far as to posit “the extinction of Homo sapiens” (C. Sagan Foreign Affairs 63, 75–77; 1984). Some regarded this apocalyptic prediction as an exercise in mythology. George Rathjens of the Massachusetts Institute of Technology protested: “Nuclear winter is the worst example of the misrepresentation of science to the public in my memory,” (see http://go.nature.com/yujz84) and climatologist Kerry Emanuel observed that the subject had “become notorious for its lack of scientific integrity” (Nature 319, 259; 1986).

Robock's single-digit fall in temperature is at odds with the subzero (about −25 °C) continental cooling originally projected for a wide spectrum of nuclear wars. Whereas Sagan predicted darkness at noon from a US–Soviet nuclear conflict, Robock projects global sunlight that is several orders of magnitude brighter for a Pakistan–India conflict — literally the difference between night and day. Since 1983, the projected worst-case cooling has fallen from a Siberian deep freeze spanning 11,000 degree-days Celsius (a measure of the severity of winters) to numbers so unseasonably small as to call the very term 'nuclear winter' into question.

Russell Seitz, Harvard University    Nature  475, 37  (07 July 2011)   Doi:10.1038/475037b

AND NOW A WORD FROM  ALAN ROBOCK & TTAPS  AUTHORS RICHARD TURCO & OWEN TOON :            

"We do not conduct detailed new studies of the smoke and dust emissions from nuclear attacks here. Rather, we chose emissions based on previous studies so as to make our results comparable to them." - Journal of Geophysical Research  JULY 2007

"1980s predictions of nuclear winter effects were, if anything, underestimates."

                                                                            -- Physics Today December 2008

OK , THEN,  LET US COMPARE BOTH ON ONE GRAPH, LIKE THIS:

The Catch-22 is that the authors are in denial- they are rejecting a decade's worth of empirical studies that gutted the guesstimates that went into their original model. They have gone back to where they started in 1983, instead of where the science ended up a decade later.

Then as now, what happens depends on what the modelers put into the model:  Not enough soot to blacken the sky?  Just inflate its lifetime to make up the difference:

Why ? Because  Precautionary Principle. And Special Sauce.It's not going down  well though-  too many scientists noticed this gambit when they tried it the first time around : 

Climate Change: Skeptics vs. Deniers

  STEPHEN H. SCHNEIDER”   Science Insider , issue 33(3):17, May/June 2009,

All good scientists are skeptical: 

I changed my mind from cooling to warming in 1974 when the preponderance of evidence shifted—and is now well established. 

I changed my views on nuclear winter making it “nuclear autumn” in 1984, incurring the wrath of the peace movement—again because the preponderance of evidence shifted with study. That is a skeptic—what all scientists should be. 

But real skeptics still accept a preponderance of carefully examined evidence even when some elements of a complex systems problem remain unresolved—and do not pretend that when there are loose ends some well-established preponderances don’t exist—that is beyond skepticism to denial—or political convenience often. 

So a skeptic questions everything but accepts what the preponderance of evidence is, and a denier falsely claims that until all aspects are resolved we know nothing and should do nothing—often motivated by the latter. If you deny a clear preponderance of evidence, you have crossed the line from legitimate skeptic to ideological denier. 

The New Republic   1987

TRB from Washington 

THE LITTLE CHILL

TRB is on vacation. This column was written

by Eliot Marshall a writer for Science

magazine.

 Three years ago Carl Sagan and a few

other scientists proposed a new theory

of Armageddon. They called it "nuclear

winter," and their message was chilling.

The end of the world, they said, would

come not by fire during a nuclear attack

but by ice, afterward. After a nuclear

war, the Earth would become encircled

with smoke, dark, and cold. 

No one could expect to survive the frost, not 

The innocent New Zealanders or the remotest

tribes of Africa. Even a small atomic war 

could end human life, Sagan concluded

in the Winter 1983 issue of Foreign Affairs

that all nuclear weapons should be eliminated,

 or at least 99 percent of them. 

This insight did not come from a rereading of

 the Book of Revelation,  It rested on modern

physics  and a very sophisticated computer 

program. It had the glint of hard science. 

Sagan, who is an expert on the solar system 

and an adviser to NASA on the Voyager

space probe, may be America's most famous 

popularize of science. In 1983 several other 

scientists, including biologist Paul Ehrlich

of Stanford, joined Sagan to endorse the

view that nuclear weapons were a threat

to the human species—nquite apart from

the obvious threat to civilized life north

of the equator. They launched a media

blitz that included heavy technical articles,

political essays, and TV interviews.

It still reverberates through literature.

The message was always the same:

scientific analysis "proves" that nuclear

weapons are useless. To employ them is

to commit global suicide. Even owning

them is dangerous because it increases

the risk of human extinction. The best

thing to do is to get rid of them. This

message came nine months after Reagan's

"Star Wars" speech, matching his

technician's dream with a technician's

nightmare of equal force.

The nuclear winter theorists wanted

publicity  back then, and they got it.

But now the situation has changed.

The death-by-ice theory seems moribund,

riddled with problems, and of

diminishing relevance to strategic policy.

The same can be said of Reagan's

idea of using space weapons to protect

cities.

The main technical challenge to nuclear

winter comes from Stephen Schneider

and Starley Thompson, researchers at

the National Center for Atmospheric Re-

search in Boulder, Colorado. They agree

with Sagan that the number of nuclear

weapons should be reduced, but they

say the integrity of atmospheric science

should not be sacrificed to make that

point. Schneider claims that it has been

clear for perhaps two years that Sagan's

original description of nuclear winter is

not the most accurate. But coaxing has

not brought any acknowledgment that

this is so. Sagan said recently that he

found "nothing new" in a state-of-theart

computer analysis by Schneider and

Thompson to change his view of

Armageddon.

Schneider and Thompson laid out

their doubts in a Foreign Affairs  article last

summer, reporting that the chance of

human extinction after a nuclear war is

"vanishingly low," They find no risk of

a new ice age. Some open, dry areas in

the war latitudes might undergo temporary

"quick freezes," But, on average,

the temperature drop in the Northern

Hemisphere would not be worse than 12

degrees during the first week or so after

an attack.

At a private gathering of experts at the

National Academy of Sciences in January,

it became clear that this new mild

version of "nuclear autumn" is credible

and may even overstate the temperature

drop. This does not mean the climatic

impacts of war would be mild, Schneider

and Thompson say that rice and soybeans

are sensitive to small temperature

changes and that global rainfall patterns

might be disrupted. Millions (billions?)

might starve. But there would be no ice

in the tropics; that is certain. Schneider

says: "Carl's idea was brilliant. He proposed

an invasion from Mars," It just

didn't hold up under scrutiny.

The more apocalyptic version of nuclear

winter has become a part of the

anti-weapons dogma of the 1980s, As a

result, some people may be reluctant to

let it go. Others will delight in its agonies.

For example, Russell Seitz, a conservative

critic writing in the National Interest,

 sees something like collusion in the

nuclear freezers' promotion of this theory

and some scientists' attempts to keep

it alive. He claims it was created by the

"psychological strategists of the peace

movement" in 1982 to give the torpid

populace a jolt. Seitz also blames it for

promoting a panic among America's allies

in the South Pacific, leading to attempts

in Australia and New Zealand to

banish U.S, nuclear ships from their

ports, Sagan and co-authors label the

Seitz article "ranting,"

Although Schneider's milder scenario

has more credibility today, the technical

argument has a long way to run.

This is because the Pentagon has been

cajoled into taking nuclear winter seriously.

The Defense and Energy Departments

have increased research on

nuclear winter from around $300,000 a

few years ago to around $5.5 million

now. It is embedded in the budget. The

amount is nothing like the $5 billion

spent on the other millennial fancy

of the 1980s, "Star Wars," and not

enough—the vested researchers say—to

provide definitive answers to the questions

Sagan has raised.

But even without definitive answers,

it may be time to say goodbye to nuclear

winter as a policy issue. If Schneider and

Thompson are right, and atmospheric

scientists seem to think they are, the climatic

impact is just one of a dozen "secondary

effects" of nuclear war that

would make life hardly worth living.

The main policy debate will continue to

focus on the "primary" effect: the use of

weapons. In this sense, nuclear winter

was a diversion, providing little insight

on how  to cooperate on arms reductions,

an area rife with distrust.

The freeze movement may have gained

a tactical victory through the promotion

of nuclear winter. It helped get attention.

But the advantage appears to have been

short-lived. Now, as the computer termites

gnaw at the data, the structure

creaks and totters. Soon it may be gone.

Perhaps if we are lucky, 1987 will bring

the final debunking of two great science

fictions of the Reagan era: nuclear winter

and Star Wars.

Here's my 1984 Foreign Affairs critique, and the WSJ's op-ed version of  the long 1986  National Interest  essay ' In From The Cold : 'nuclear winter ' melts down' , from which this figure is taken:

The Melting of 'Nuclear Winter'   1986

The End Of The World isn't what it used to be.

Nuclear Winter', the theory launched [in 1984] that predicted ...a nuclear exchange as small as 100 megatons ("a pure tactical war, in Europe, say" in Carl Sagan's phrase), in addition to its lethal primary effects, would fill the sky with smoke and dust, ushering in life-extinguishing sub-zero darkness, has been laid to rest in the semantic potter's field alongside the "Energy Crisis" and the "Population Bomb."  Cause of death:  notorious lack of scientific integrity.

The Nuclear Winter conjecture has unraveled under scrutiny.  Yet not so long ago, policy analysts took it so seriously that there is reason to examine how the powerful synergy of environmental concern and the politics disarmament drove some scientists to forge an unholy alliance with Madison Avenue.  Mere software has been advertised as hard scientific fact. How did this polarization arise?

     In 1982, a question arose within the inner circle of disarmament activists:  Could the moral force of Jonathan Schell's eloquent call to lay down arms, "The Fate of the Earth," be transformed into a scientific imperative?  Peace-movement strategists wanted something new to dramatize
nuclear war's horrors.  As Ralph K. White put it in his book "The Fearful Warriors":  "Horror is needed.  The peace movement cannot do without it."

What they got was surreal -- a secular apocalypse.

     A 1982 special issue of the Swedish environmental science journal Ambio considered the environmental consequences of a nuclear war. This special issue did little to evoke a mass response of the sort needed to change the course of strategic doctrine.  But one article contained the
seed of what would become Nuclear Winter.

     Mr. Sagan seized upon an article by Messrs. Paul Crutzen and John Birks that raised the question of a "Twilight at Noon" if the fires ignited by nuclear holocaust were to convert much of the fuel in both woodlands and cities into enough soot to enshroud the globe.  In the hands of others their concerns would be transformed into an exhortation.

     The chilling climatic impact of this soot can be modeled with existing software.  The paper that resulted came to be known as TTAPS, after the initials of its authors beginning with Richard Turco and ending with Carl Sagan.

    Audubon Society president Russell Peterson, a friend of Ambio's editor, sent the issue to Robert Scrivner of the Rockefeller Family Fund. Mr. Scrivner convened an ad hoc consortium of foundations and scientific groups with a bent for disarmament.  Cornell astrophysicist and media personality  Carl Sagan assembled a scientific advisory board that drew heavily from such organizations as the Union of Concerned Scientists, Physicians for Social Responsibility, the Federation of American Scientists and the Natural Resources Defense Council.  Two-dozen foundations and more than 100 scientists were recruited.

A BONE-DRY BILLIARD BALL

     Nuclear Winter never existed outside of a computer, except as a painting commissioned by a PR firm.  Instead of an earth with continents and oceans, the TTAPS model postulated a featureless, bone-dry billiard ball.  Instead of nights and days, it postulated 24-hour sunlight at one- third strength.  Instead of realistic smoke emissions, a 10-mile-thick soot cloud magically materialized, creating an alien sky as black as the ink you are reading.  

The model dealt with such complications as geography, winds, sunrise, sunset and patchy clouds in a stunningly elegant manner -- they were ignored.  When later computer models incorporated these elements, the flat black sky of TTAPS fell apart into a pale and broken shadow that traveled less far and dissipated more quickly.

      The TTAPS model entailed a long series of conjectures:  if this much smoke goes up, if it is this dense, if it moves like this, and so on.  The improbability of a string of 40 such coin tosses coming up heads approaches that of a pat royal flush.  Yet it was represented as a "sophisticated one- dimensional model" -- a usage that is oxymoronic, unless applied to Twiggy.

     To the limitations of the software were added those of the data.  It was an unknown and very complex topic, hard data was scant, so guesstimates prevailed.  Not only were these educated guesses rampant throughout the process, but it was deemed prudent, given the gravity of the subject, to lean toward the worst-case end of the spectrum for dozens of the numbers involved.  Political considerations subliminally skewed the model away from natural history, while seeming to make the expression "nuclear freeze" a part of it.

     "The question of peer review is essential.  That is why we have delayed so long in the publication of these dire results," said Carl Sagan
in late 1983.  But instead of going through the ordinary peer-review process, the TTAPS study had been conveyed by Mr. Sagan and his colleagues to a chosen few at a closed meeting in April 1983.  Despite Mr. Sagan's claim of responsible delay, before this peculiar review process had even begun, an $80,000 retainer was paid to Porter-Novelli Associates, a Washington, D.C., public-relations firm.  More money was spent in the 1984 fiscal year on video and advertising than on doing the science.

     The meeting did not go smoothly; most participants I interviewed did not describe the reception accorded the Nuclear Winter theory as cordial or consensual.  The proceedings were tape recorded, but Mr. Sagan has
repeatedly refused to release the meeting's transcript.  (The organizers have said it was closed to the press to avoid sensationalism and premature disclosure.)  According to Dr. Kosta Tsipis of MIT, even a Soviet scientist
at the meeting said, "You guys are fools.  You can't use mathematical models like these to model perturbed states of the atmosphere.  You're playing with toys."

     Having premiered on Oct. 30, 1983,( the anniversary of Orson Welles War of The Worlds Broadcast) as an article by Mr. Sagan in the Sunday supplement Parade, the TTAPS results finally appeared in Science magazine (Dec. 23, 1983).  This is the very apex of scholarly publication,customarily reserved for a review article expounding a mature addition to
an existing scientific disipline -- one that has withstood the testing of its data and hypotheses by reproducible experiments recorded in the peer-reviewed literature.  Yet what became of the many complex and uncertain variables necessary to operate the Nuclear Winter model?  They were not set forth in the text -- 136 pages of data were instead reduced to a reference that said, simply, "In preparation."  The critical details were missing. They have languished in unpublished obscurity ever since.

     The readers of Science were still bewildered when, just one week later, another article by Mr. Sagan -- "Nuclear War and Climatic Catastrophe" -- appeared in Foreign Affairs.  Mr. Sagan argued that, because of the TTAPS results, "What is urgently required is a coherent, mutually agreed upon, long-term policy for dramatic reductions in nuclear armaments..."

     In hastening to maximize the impact, Mr. Sagan made mistakes.  While he cited the following passage as coming from a companion piece in Science that he had co-authored, it did not actually appear in the published version of that article:  "In almost any realistic case involving nuclear exchanges between the superpowers, global environmental changes sufficient to cause an extinction event equal to or more severe than that of the close of the Cretaceous when the dinosaurs and many other species died out are likely.  (Emphasis added)." The ominous rhetoric italicized in this passage puts even the 100 megaton scenario of TTAPS on a par with the 100 million megaton blast of an asteroid striking the Earth.  This astronomical mega-hype failed to pass peer review and never appeared in Science. Yet, having appeared in Foreign Affairs, it has been repeatedly cited in the literature of strategic doctrine as evidence.

     Rather than "higher standards of evidence," Mr. Sagan merely provided testimonials.  He had sent return-mail questionnaires to the nearly 100 participants at the April meeting, and edited the replies down to his favorite two-dozen quotations. What became of the hard copy of the less enthusiastic reports remains a mystery, but it is evident from subsequent comments by their authors that TTAPS received less than the unanimous endorsement of "a large number of scientists."  Prof. Victor Weisskopf of MIT, sized up the matter in early 1984:  "Ah! Nuclear Winter!  The science is terrible, but, perhaps the psychology is good."

     Many scientists were reluctant to speak out, perhaps for fear of being denounced as reactionaries or closet Strangeloves.  For example, physicist Freeman Dyson of the Institute for Advanced Studies at Princeton was privately critical in early 1984. As he put it,"It's (TTAPS) an absolutely atrocious piece of science, but I quite despair of setting the public record straight....Who wants to be accused of being in favor of nuclear war?"

     Most of the intellectual tools necessary to demolish TTAPS's bleak vision were already around then, but not the will to use them.  From respected scientists one heard this:

  "You know, I really don't think these guys know what they're talking about."
 (Nobel laureate physicist Richard Feynman);

 "They stacked the deck" (Prof. Michael McElroy, Harvard);

and, after a journalist's caution against four-letter words,

 "Humbug is six " (Prof. Jonathan Katz, George Washington University.)

     In 1985, a series of unheralded and completely unpublicized studies started to appear in learned journals -- studies that, piece by piece, started to fill in the blanks in the climate-modeling process that had previously ben patched over with "educated" guesses.

     The result was straightforward:  As the science progressed and more authentic sophistication was achieved in newer and more elegant models, the postulated effects headed downhill.  By 1986, these worst-case effects had melted down from a year of arctic darkness to warmer temperatures than the cool months in Palm Beach!  A new paradigm of broken clouds and cool spots had emerged.  The once global hard frost had retreated back to the northern tundra.  Mr. Sagan's elaborate conjecture had fallen prey to Murphy's lesser known Second Law:  If everything must go wrong, don't bet on it.

     By June 1986 it was over:  In a Summer 1986 Foreign Affairs article enttled 'Nuclear Winter' Reconsidered, National Center for Atmospheric Research (NCAR) scientists Starley Thompson and Stephen Schneider declared, "...on scientific grounds the global apocalyptic conclusions of the initial nuclear winter hypothesis can now be relegated to a vanishingly low level of probability."

     Yet the activist wing of the international scientific estabishment had already announced the results of the first generations of interdisciplinary ecological and climatological studies based on Nuclear Winter. Journalists paid more attention to the press releases than the substance of  already obsolescent efforts at ecological modeling, and proceeded to inform the public that things were looking worse than ever.  Bold headlines carried casualty estimates that ran into the proverbial "billions and billions."

     This process culminated in the reception given the 1985 report of the National Academy of Sciences (NAS).  Stressing the uncertainties that plagued the calculations then and now, it scrupulously excluded the expression "Nuclear Winter" from its 193 pages of sober text, but the report's press release was prefaced "Nuclear Winter...'Clear Possibility.'" Mr. Sagan construed the reports to constitute an endorsement of the theory.

     But in February 1986, NCAR's Dr. Schneider quietly informed a gathering at the NASA-Ames Laboratory that Nuclear Winter had succumbed to scientific progress and that, "in a severe" 6,500-megaton strategic exchange, "The Day After" might witness July temperatures upwards of  50 plus degrees Fahrenheit in mid-America.  The depths of Nuclear Winter could no longer easily be distinguished from the coolest days of summer.

     As the truth slowly emerged, private skepticism turned often to public outrage, and not just among the "hawks." Prof. George Rathjens of MIT, chairman of the Council for a Livable World, offered this judgement: Nuclear Winter is the worst example of the misrepresentation of science to the public in my memory."

POLITICAL SCIENCE

     On Jan. 23, 1986, Pofessor Kerry Emmanuel of MIT , writing in  the leading British scientific journal Nature pronounced on the political erosion of the objectivity vital to scientific endeavor: "Nowhere is this more evident than in the recent iterature on 'Nuclear Winter,' research which has become notorious for its lack of scientific integrity."

     But it is by no means solely within the halls of science that
responsibility lies or where redress and the prevention of a recurrence must be sought.  Policy analysts have shown themselves to be the lawful prey of software salesmen.  They seem to be chronically incapable of
distinguishing where science leaves off and the polemical abuse of global- systems modeling begins.  The results of this confusion can be serious indeed.  Doesn't anybody remember the last example of the "Garbage In,
Garbage Out" phenomenon -- the "Energy Crisis"?  That crisis also began as a curve plotted by a computer.  But it ended as "The Oil Glut."  Factoids, scientific or economic, have a strange life of their own; woe to the polity that ignores the interaction of science, myth and the popular imagination
in the age of the electronic media.

     To historians of science, the Nuclear Winter episode may seem a bizarre comedy of manners; having known sin at Hiroshima, physics was bound to run into advertising sooner or later.  But what about the politics of this issue?  Does all this matter?  Mr. Sagan evidently thinks it does. 

His homiletic overkill has been relentless.  An animated version of his obsolete apocalypse has been added to his updated documentary Cosmos -- A Special Edition. This fall, prime-time audiences will watch in horror as the airbrushed edge of nuclear darknes overspreads planet Earth.  Marshall McLuhan was right on the mark -- with television's advent, advertising hasbecome more important than products.

     What is being advertised is not science but a pernicious fantasy that strikes at the very foundation of crisis management, one that attempts to the transform NATO's doctrine of flexible response into a dangerous vision.  For despite its scientific demise, the specter of Nuclear Winter
is haunting Europe, Soviet propagandists have seized upon Nuclear Winter in their efforts to debilitate the political will of the Alliance.  What more destabilizing fantasy than the equation of theater deterrence with a global Gotterdammerung could they dream of?  What could be more dangerous than to invite the Soviets that the Alliance is self-deterred -- and thus at the mercy of those who possess so ominous an advantage in conventional forces?

   The Roman historian Livy observed that "where there is less fear, there is generally less danger."  Until those who have put activism before objectivity come to apprehend this, nuclear illusions, some spontaneous and some carefully fostered, will continue to haunt the myth-loving animal that is man.

                         __________________

     Mr. Seitz is a Visiting Scholar in Harvard University's Center for
International Affairs.  This draws on   his article in the Fall 1986 issue of
The National Interest. and peer reviewed  1985 and  1986 publications in Nature

The New York Times

Nuclear Winter Theorists Pull Back

By MALCOLM W. BROWNE

Published: January 23, 1990

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SINCE 1983, scientists have been bitterly divided over whether a nuclear war is likely to result in a catastrophic global chilling. But the five scientists who introduced the term ''nuclear winter'' now acknowledge that they overestimated its severity, and their concession appears to have moderated the longstanding debate. 

Scientists say the issues involved are as pertinent to human survival as ever, despite the new friendliness of Soviet-American relations. The strategic nuclear arsensals of both nations remain intact, they note, and could come into play if the current peaceful climate gives way to war. 

The techniques developed to predict the effects of nuclear war on climate are also applicable to other climatic predictions, including the possibility that increased carbon dioxide in the air is leading to global warming, theorists say. The nuclear winter scenario is also closely related to the theory that dinosaurs became extinct when a giant meteor hit the earth and threw up a global dust cloud that caused catastrophic cooling. 

The views of atmospheric scientists studying the nuclear winter theory still vary widely, although most of those interviewed said they believe a nuclear war could have some effect on climate. But most discounted the extreme view that global chilling of the atmosphere would be severe enough to be described as ''winter.'' Scientists specializing in such studies also generally reject the suggestion that a ''nuclear winter,'' in itself, could bring about the extinction of the human race. Even Dr. Richard P. Turco, the physicist who coined the phrase ''nuclear winter,'' discounts the idea. 

Dr. Turco, a professor of atmospheric science at the University of California at Los Angeles, said in an interview that he had never believed that nuclear winter alone could wipe out humanity. ''That was a speculation of others, including Carl Sagan,'' he said. ''My personal opinion is that the human race wouldn't become extinct, but civilization as we know it certainly would.'' 

Dr. Sagan, a professor of astrophysics at Cornell University, was one of the scientists who collaborated with Dr. Turco in the article that ignited the nuclear winter dispute. The article, ''Nuclear Winter: Global Consequences of Multiple Nuclear Explosions,'' was published by the journal Science in 1983, and spawned a host of movies, plays and books predicated on the nuclear winter hypothesis. 

The other authors of the article were Dr. Owen Brian Toon and Dr. James B. Pollack, both of the National Aeronautics and Space Administration's Ames Research Center, and Dr. Thomas P. Ackerman of Pennsylvania State University. Their paper became so famous and so frequently cited that other scientists have since referred to it by an acronym of the contributors' initials: TTAPS, pronounced ''tee-taps.'' 

That paper was not the first suggestion that global cooling might follow a nuclear exchange. A 1982 article by Dr. Paul J. Crutzen of the Max Planck Institute in West Germany and Dr. John W. Birks of the University of Colorado proposed the possibility of such an effect. 

In a new paper published in Science, ''Climate and Smoke: An Appraisal of Nuclear Winter,'' the five TTAPS scientists review research conducted during the five years after their first joint paper. Drop in Temperatures While asserting that their general conclusions have been sustained, they say that a full-scale nuclear exchange in midsummer could reduce temperatures by an average of only 10 to 20 degrees centigrade (18 to 36 degrees Fahrenheit) in northern mid-latitudes. Compared with the reduction of 15 to 25 degrees centigrade (27 to 45 degrees Fahrenheit) predicted by their first paper, this chilling would be relatively mild, and in the view of some scientists, it deprives the phrase ''nuclear winter'' of realistic meaning. 

Dr. Turco said his nuclear winter forecast had changed somewhat because he and his colleagues had been able to reduce the uncertainty inherent in some of the climatic effects involved. New experimental data and analyses from other groups also helped to refine his predictions, he said. 

Dr. Stephen H. Schneider of the National Center for Atmospheric Research in Boulder, Colo., a long-standing critic of the extreme nuclear winter hypothesis, believes that a cooling of 10 to 20 degrees centigrade (18 to 36 degrees Fahrenheit) would not constitute the arrival of ''winter.'' 

''I would call it nuclear fall, not winter,'' Dr. Schneider said in an interview. ''But in any case, the TTAPS numbers have now more or less converged with ours, so I don't have a major problem with them anymore.'' 

In their latest paper, Dr. Turco and his associates say they have summarized and synthesized important experimental evidence and mathematical predictions made by other groups related to nuclear winter, thereby reducing the uncertainties inherent in their theory. 

''Essentially,'' Dr. Turco said, ''what we say is that the basic physics we proposed turned out to be correct, although the magnitude of the effects has been moderated somewhat.'' Blocking of Sunlight The theory underlying nuclear winter is that if the Soviet Union and the United States were to wage an unlimited nuclear war, much of the resulting dust and smoke from fires, especially those of burning cities, would be spewed into the upper atmosphere, where it might remain for weeks or months. This would block sunlight, resulting in a sudden drop in atmospheric temperature. 

The latest paper suggests some additional atmospheric effects of an all-out nuclear war, notably a severe depletion of the ozone layer in the Northern Hemisphere, which protects human beings from dangerous solar ultraviolet radiation. 

But although most critics of the nuclear winter theory have expressed only muted disagreement with the latest TTAPS paper, major discrepancies remain between its estimates and those of some other leading investigators. 

An important factor in such estimates, all agree, is the quantity of combustible material that would contribute to the global pall of smoke. Based on estimates by various research groups, Dr. Turco assumes the total mass of material burned, including wood, plastics, petroleum and vegetation, would be 5,075 ''teragrams'' (trillions of grams), or about 6.8 billion tons. 

But another leading investigator, Dr. Richard D. Small, a thermal science expert at Pacific-Sierra Research Corporation, a Los Angeles research organization, says he disagrees strongly with this estimate, which he believes is much too high. 

Dr. Small estimates that a maximum of 1,475 teragrams of material would be burned in the United States, provided all the weapons in the Soviet arsenal were successfully launched and detonated, and that all combustible material was actually ignited. Comparable figures for burned material in Europe and the Soviet Union would be proportionately less, ''because those regions simply have less combustible material in homes, businesses and industries,'' he said. 

''Our estimate is based on rigorous analysis of blueprints and other records of real homes and commercial and industrial structures,'' Dr. Small said. ''We add up every possible ingredient available for burning to estimate a weighted total.'' 

The greatest uncertainty in the article's assumptions, he said, is in the amount of smoke that would be injected into the atmosphere, remaining aloft long enough to reduce global temperatures. 

Other uncertainties include the amount of smoke that would be removed from the atmosphere by rain, and the height to which smoke would be lifted by fires ignited in a nuclear exchange. These and other factors could radically change the atmospheric effects. Biggest Uncertainty ''Perhaps the largest uncertainty is timing,'' Dr. Schneider said. A nuclear exchange in late spring or summer might have a significant effect on temperature, while a war in late fall or winter would have no appreciable effect, because sunlight is already reduced and temperatures are already low, he said. The growing season, moreover, would be over, and therefore unaffected by cooling. 

Dr. George Rathjens, a professor of political science at the Massachusetts Institute of Technology, charged in an interview that ''all the hype about a lot of freezing following a nuclear exchange is hyperbole.'' He said his own calculations, using the latest of Dr. Small's numerical smoke estimates in a standard mathematical model, result in a temperature drop of only about 9 degrees centigrade (16 degrees Fahrenheit) after a full-scale nuclear war in the Northern Hemisphere in midsummer. 

''I remain unconvinced that the TTAPS authors have a robust basis for their conclusions,'' he said, ''although in their latest paper they have made a fair number of concessions consistent with the work of others.'' 

Russell Seitz, whose critical analysis of the nuclear winter hypothesis attracted wide attention while he was a visiting scholar at Harvard University, is also unconvinced by the latest TTAPS paper. He said it is ''blatant semantic aggression'' to describe the available scientific data as pointing to a nuclear winter. 

In reply to Dr. Rathjens and Mr. Seitz, Dr. Turco characterized them as ''nonspecialists with political axes to grind and who have no real technical background. 

Dr. Turco said he and Dr. Sagan are about to publish a book, ''Nuclear Winter and an End to the Arms Race,'' in which they advocate reducing Soviet and American arsenals of nuclear warheads to a few hundred each. Link to Dinosaur Theory The scientific issues involved in the nuclear winter debate stem directly from a parallel debate concerning the reasons dinosaurs became extinct. In 1979, the late Dr. Luis Alvarez of the Lawrence Berkeley Laboratory in California; his son, Dr. Walter Alvarez of the University of California at Berkeley, and their colleagues proposed a new explanation for the extinction of dinosaurs and many other forms of life 65 million years ago at the close of the Cretaceous period. 

They theorized that the earth was struck by an asteroid or comet, which threw up an immense dust cloud that quickly blanketed the planet. They believe the cloud blocked sunlight, chilled the atmosphere and interfered with the photosynthetic process on which plants depend. The result, they hypothesized, was a mass extinction of the dinosaurs. That theory led directly to the nuclear winter hypothesis. The impact hypothesis has been challenged by paleontologists who believe that the extinction of dinosaurs had more complicated causes. Some paleontologists believe that if changing climate was a reason, it was probably caused by dust and gases from a continent-sized volcanic eruption in what is now India. Others believe that falling sea levels, disease and other factors caused the extinctions. 

Now that the nuclear winter debate appears to center more on technical issues than personalities, participants hope it will cool. ''It's nice to see these guys acting like scientists again,'' a researcher said. 

Nuclear Winter: Debated Points 

The dispute over whether a nuclear war would cause a ''nuclear winter,'' fatal to human life on earth, hinges on these variables: 

CONFLAGRATION 

How much flammable material is available to burn? Would fires be in urban areas, with presumably more combustible material? 

ATMOSPHERIC DYNAMICS 

Would dust and smoke injected into the upper atmosphere remain there to reduce global temperatures, or would much of it precipitate as ''black rain?'' 

TIMING 

Would the fires be in spring or summer, or in fall or winter, when temperatures are already low? 

DARKNESS 

How much light-blocking effect would the soot from the fires have? 

Photos: Dr. Richard P. Turco (NYT/Marty Katz); Dr. Stephen H. Schneider (pg. C8)

Historical postscript 

As the Kuwait oil fires began in 1991 , Sagan appeared on NBC Nightline and predicted that the apocalyptic firestorms and black skies would collapse the monsoonal circulation and doom  Asia to starve beneath a frigid pall.

 It didn't happen.