March 1985 Science Digest cover story by Andrew Revkin on the science behind "Nuclear Winter" -- the hypothesis that smoke from incinerated cities after a nuclear war could blot the sun and cause calamitous widespread cooling and, possibly, famine. Much has been learned since. Many scientists still see a significant risk. Particularly notable is the body of work by Alan Robock at Rutgers University: http://climate.envsci.rutgers.edu/robock/robock_nwpapers.html More at Dot Earth: http://dotearth.blogs.nytimes.com/?s=%22nuclear+winter%22

2. - ~ - -- - -~-
Everyone knew
that nuclear war would
be hideous, but no
one expeaed this.
arly in 1979, the Congressional Office of Technol-
E ogy Assessment (OTA) completed a 151-page re--
port called "The Effects of Nuclear War."The first
finding, set off in boldface, was "The effects of a
nuclear war that cannot be calculated are at
least as important as those for which calculations are at-
tempted "That has proved to be an unusually apt caveat.
Now, only a few years after the OTA report, and four de--
cades after the invention of nuclear weapons, the scientific
and defense communities have suddenly learned of an as-
pect of nuclear war, overlooked by OTA and almost every-
one else who had studied the subject, that could prove to
be more devastating than any of the other effects--includ-
ing the blast and radiation.
The forgotten factor? Smoke. Government scfendm
had been studying the physical effects of nuclear aplo-
sions for decades, had produced massive wlumiel , . of
detailed observations, had scrutinized &CCOUDII of lbe
blasts at Hiroshima and Nagasaki, the lln!stonDs at 0...
HARD den, Hamburg and Tokyo. But no one bad calnaleled tbe!
climatological effects of the globe-&paoDJDg paD of ~
FACTS smoke that could rise from tbe lbousaodl of files ...........
"!0
by a nuclear war. Indeed. wltb the ezcepllon of
glected reports produced for tbe U.S. government In ~
~
ABOUT 1960s, the word smoke is baldly meotloaed in lbe ldeodl-
ic literature.
Joumal~
I
NUCLEAR A paper publlsbed In lbe Swedish
1982 thus came 11 a complete surprise. stunning
and defeDse aped~ alike wltb Its slmpJe. ominous
WINTER JolmBIIb,mAmodcaD........._~'"=~
uct;
sion. Paul Crutzen, a Dutch atmospbertc ldentlst.
BY ANDREW C. REVKIN s.n1tw,.,. Andrlw c RaJidn Is 1«11ur«1 on tlw ~ ,._

3. NUCLEAR WINTER
have a major Impact on climate-
The biologists said that lthe manifested by significant surface
darkening over many weeks, sub-
possibility of the extinction of freezing land temperatures persisting
for up to several months, large pertur-
Homo sapiens cannot be excluded." bations in global circulation patterns
and dramatic changes in local weath-
er and precipitation rates-a harsh
'nuclear winter' in any season."
The biologists also presented theh
findings. Their sweeping, controver-
sial conclusion, later published in the
same issue of Science. was that such a
climatic catastrophe could "cause the
extinction of a major fraction of the
plant and animal species on the
Earth.... In that event. the possibili~
of the extinction of Homo sapiens
cannot be excluded."
The press, fresh from reporting on
The shock waw loYOUid exlfngulsh some of 1he ftres set by Che President Reagan's Star WatS defense initiative and the
lUst's thermal pulSe, but It wouJd •rso start l'l'l)'l1ad sec:oncs.ry
ftres by bt'U.k fng g.s lines, fuel atnla and the Uke. GM!n 1he antinuclear protests in Europe. gave the news wide cover-
right amdlttons, the ftres CXKild merge Into il single lrRino. age. The public was already sensitized to the issue by ad·
vertisements for the ABC special ''The Day After," whict.
tary but convincing way that smoke from a nuclear war- was aired just three weeks later.
several hundred million tons of it-"would strongly restrict To be sure, not everyone agreed. A small but powerfu.
the penetration of sunlight to the Earth's surface and cadre of critics, led by Edward Teller, a chief architect o:
change the physical properties of the Earth's atmosphere." the hydrogen bomb and an important force at Lawrence
And theh calculations were based only on smoke from Uvermore National Laboratory, attacked the reports, argt!-
burning forests. When another research team considered ing that the studies were inconclusive and politically motl-
smoke from burning cities, the forgotten factor took on vated. "The only news," Teller says, "is that Sagan has
even more significance. made a lot of propaganda about a very doubtful effect''
Richard Turco, an atmospheric scientist at R & D Asso-
ciates, in Marina del Rey, California, had been working hree congressional hearings, dozens of scientific
with three researchers at the NASA Ames Research Center,
two of whom were former students of Cornell astronomer
Carl Sagan, on the atmospheric effects of dust raised by nu-
clear explosions. When Turco read an advance copy of the
Ambio study, be hnmediately saw that smoke would be far
more important than dust
Turco reworked the Ambio calculations, adding in the
T meetings, several international conferences anG
at least four books later, nuclear winter has tak·
en its place-somewhere between megaton ana
ouerki/1-in the burgeoning lexicon of terms
spawned by the study of nuclear war. After more than a
year of scrutiny, the TTAPS study bas held up, at least as a
"first order" estimate. "Critics of the original paper proba-
smoke from burning cities. Along with the NASA group- bly never read it," says Startey Thompson, an aunospheri.;;
O. Brian Toon, Thomas Ackerman and James Pollack- scientist at the National Center for Atmospheric Research
and Carl Sagan, he put together a comprehensive analysis, (NCAR), i.n Boulder, Colorado, who bas contributed to se-:-
including computer models, of the "global consequences eral subsequent computer analyses of the concept "If th~.
of multiple nuclear explosions." The group, which soon had read it carefully they would realize it's not very O'er-
became known as TTAPS (an acronym based on last stated. It has lots of caveats in it What has probably been
names), discovered that the smoke could have a devastat- overstated has been public discussion. When you put It a..
ing effect on the Earth's climate. together, it looks bad."
The findings were so dramatic, in fact, that in late April Almost everyone agrees on one point the need fo~
1983, more than 100 scientists were invited to a closed ses- more research. " It's been an instant field," says Bob Cess
sion at the American Academy of Arts and Sciences, in a specialist in clhnate modeling at the State University o::
Cambridge, Massachusetts, to review the study. The physi- New York, Stony Brook, who is working on the problerr.
cal scientists met first, testing the assumptions, dissecting with researchers at Lawrence Uvermore. "Never has sc
the models, checking the data. Some adjustments and re- much been said about a field in which so little has be-er.
finements were made, but the basic conclusions held. done."
Then the biologists took a crack at it They extrapolated The only absolute quantity in the entire concept is the
from the climatic effects to the impact on agriculture and fantastic power of the bomb. The uncertainties are mul:i-
ecosystems. The destruction wrought by nuclear war, they fold and frustratingly complex. Many aspects of the micro-
concluded, would be much greater and more long-lived physics of lire and smoke and the macropbysics of weat."l-
than anyone had previously conceived. er and climate are still mysteries. in fact, S. Fred Singer c.
The results were announced to a capacity crowd at a geophysicist at George Mason University in Fairfax, Virgm-
conference in Washington, D.C., on Halloween 1983 and ia, and a consistent critic of the TTAPS work, has argued .~
were published in the December 23 issue of Science. The both Nature and the Wall Street Journal that, given lt.e
TTAPS group concluded that "a global nuclear war could right conditions, a nuclear war could produce a dark. h :1t
64 SCENCE OIGEST-MAACH 1985

4. ···nuclear summer." Moreover, the computer-generated its bottle since it was unleashed on Japan 40 years ago. If
models being used to study nuclear winter are---<lespite nuclear winter is proved plausible, MAD may be replaced
the advent of supercomputers and weather satellites--still by a simpler form of deterrence, assured self-destruction,
patchwork attempts to simulate the global climate. which guarantees that a nation launching a nuclear attack
The formula for nuclear winter is rife with variables as will in effect be committing suicide.
well as uncertainties. What type of nuclear war might be According to Sagan and many others, nuclear winter is
fought? How many warheads, of what megatonnage, thus an unexpected panacea. delivered in the nick of time,
would be exploded? (One megaton is the explosive power that may make nuclear weapons "obsolete" by turning
of one million tons of TNT-an amount of explosives that them against their users. But others, including Freeman
would fill a freight train 300 miles long.) Are the targets Dyson, a physicist at the Institute for Advanced Study, in
"bard" or "soft," silos or cities? Does the war last a day, a Princeton, and the author of Weapons and Hope, predict
week, months? Does it take place in summer, in the middle that if the theory is confirmed, it could create a new, dan-
of the growing season, or in the chill of winter, when a gerous arms race-a race among military planners to
drop in temperature might do less damage? make nuclear war "safe" again.
Yet another sticking point has been finding reasonable
numbers to substitute for these variables. Most of them are pelled out, the theory of nuclear winter is as sim-
secrets, embedded in the closely guarded targeting scenar-
ios and combat strategies of the United States and the Sovi-
et Union.
In December, the National Research Council published
an exhaustive review of "the effects on the atmosphere of
S ple as the chill you feel when a cloud passes in
front of the sun, and it is as complex as the ever-
changing patterns of wind and weather that swirl
daily across the surface of the globe.
It is based on phenomena as minute as the behavior of
a major nuclear exchange." Their best estimate was that the individual particles within a cloud of smoke and on
there is a "clear possibility'' that nuclear war would lead to events as massive as the explosion of a thermonuclear
nuclear winter. Their main conclusion was a call for more warhead with the force of 2 billion pounds of TNT.
research. Soon after, Alan Hecht. director of the National In general, the theory holds that the sun-hot fireballs of
Climate Program Office of the National Oceanic and Atmo- thousands of exploding warheads would set forests, fields
spheric Administration, submitted a plan for a five-year and, especially important, cities ablaze, lofting plumes of
program of research on nuclear winter to President Rea- dark smoke near the boundary between the troposphere-
gan's science adviser. The program will focus on climate the lowest region of the atmosphere, where weather oc-
models and the physics of smoke. curs-and the stratosphere, the static, weatherless region
While government has slowly been getting into gear, that starts six to eight miles up.
scientists at institutions as disparate as Lawrence Uver- Cities are important because they are loaded with
more, which is one of the nation's
leading weapons laboratories, and
universities such as Cornell and Colo-
rado State are devoting spare hours
and odd scraps of funding and com-
puter time to nuclear-winter studies.
Some are refining mathematical mod-
..
els of fires and climate that are testing
the limits of supercomputer technolo-
gy. Others are looking to the past,
even to other planets, to try to find
events, such as volcanic eruptions,
dust storms and meteor impacts, that
might provide useful analogies to
some of the effects of nuclear war.
And biologists, who have been largely
left out of the federal plan, are hoping
to increase general understanding of
the ecological consequences of nucle-
ar winter.
The stakes are high- as high as
can be. If the probable outcome of a
nuclear war is a nuclear winter, non-
combatant nations can no longer con-
sider themselves outside the fray. As
for the members of the nuclear frater-
nity, particularly the United States and
the Soviet Union, the implications for
military strategy, civil defense and
arms control are vasl
The long-standing balance of ter- 1he bombing of the German city of Dresden In 1945 produced one ofthe ftrst, and most
destructtve, marHNide ftrestonns In h.::?.'. Almost 1KfY flllrrm111ble material within
ror, called mutual assured destruction an elghMqullre-mlle area was Jndne . Winds of nuf'ftmtcane fonle toppled
(MAD), has kept the nuclear genie in trees and fanned the flllmes. Jt Is estimated that at leat 35,000 people perished.
65

5. NUCLEAR MNTER
Earth radiates this energy back toward
The smoke cloud, and thus the space in a different form, as infrared
radiation (IR).
cold and dark, could spread across Fortunately for humans and other
life forms, not all of the radiation es-
sensitive tropical ecosystems. capes into space. If it did, the Earth
would have a surface temperature be-
low zero Fahrenheit. The heat is
trapped by the so-called greenhouse
effect As TIAPS explains, "The atmo-
sphere generally ads as a window for
sunlight but a blanket for heat" Car-
bon dioxide, water vapor and the wa.
ter in clouds all absorb some of the es-
caping energy. The air nearest the
surface absorbs the most heat. giving
Earth its 56-degree-Fahrenheit aver-
age surface temperature. But the air
cools rapidly with increasing altitude,
to about -67 degrees at the upper Urn-
it of the troposphere. The entire troposphere is stirred up
and set into motion when the low, heated air masses
rise-a process called convection. This is the main source
of weather: clouds, wind and precipitation.
fuel-plastics and petroleum, wood and paper. Reservoirs Smoke has optical properties that make it a better
of oll and gasoline, dense downtowns and sprawling blocker of sunlight than dust or water clouds. VISible light
neighborhoods of wood-frame houses and tenements give is transmitted at wavelengths of between 0.4 and 0.7 mi-
cities their high fuel density. Moreover, petroleum and crons (a micron is a millionth of a meter). A significant
plastics produce more, and darker, smoke than wood ln fraction of the particles in smoke are less than a mlaon in
fact, Art Broyles, a physicist and fire expert at the Universi- diameter. Dark particles of this size are ideally suited to ab-
ty of Aorida, estimates that even though these materials sorbing energy at those wavelengths.
make up only about 5 percent of the fuel in cities, they The result? If enough cities are bumed-and according
would probably produce as much smoke as the rest of the to one of the TIAPS scenarios, 100 dties will suffice-the
fuel, which is primarily wood. atmosphere will be turned on its head. Sunlight will be ab-
The individual clouds of smoke would coalesce after a sorbed not at the surface but by the layer of smoke in the
week or two. Pushed by strong west-to-east winds, the upper troposphere. The smoke and the troposphere will
smoke would form a uniform belt of particles girdling the heat up, and the Earth below, deprived of up to 95 percent
Northern Hemisphere from 30 to 60 degrees latitude, a re- of its daily ration of solar energy, will cool.
gion that reaches from central Aorida to southern Alaska. The TTAPS group calls this the "anti-greenhouse ef.
The weapons' blasts would also raise tons of dust into tbe feet" One consequence of such a mass inversion would
stratosphere, where it can remain for years. be a lack of convection. With few rising pockets of heated
air, there would be little atmospheric turbulence, fewer
be smoke, and to a much smaller extent the dust, storms and thus less of the natural "scavenging" process- ~
T would prevent all but a tiny fraction of sunlight
from reaching the surface of the Earth in the
Northern Hemisphere for weeks, possibly
months. According to the TIAPS study, after a
"baseline," or medium·size, nuclear war, in which war-
heads with a total yield of 5,000 megatons were exploded
over a variety of targets, average surface temperatures
es, including rain, that normally remove particles from the
air. To make matters worse, as the smoke-laden air in the
upper troposphere grew warmer, it would tend to rise even
higher, taking it farther from the region of cleansing predp-
itation, perhaps as high as the stagnant stratosphere. The
nuclear-winter effect, in Sagan's opinion, could thus be
self-perpetuating.
i
I
i
5
~
I
s
would drop 60 degrees Fahrenheit-below freezing even
in summer-destroying agriculture, disrupting ecosystems
and making the postwar world a nightmarish mix of cold,
The TTAPS researchers are the first to point out that
their effort involved many assumptions. The model they
used to chart the temperature prome of the atmosphere
i
~
dark and starvation for those humans who survived the was one-dimensional, representing the averaged global at- l
other effects. The study also projects the possibility that the mosphere as a single column of air. The smoke for each of ~
high-altitude smoke cloud, and thus the cold and dark, several dozen different war scenarios was assumed to be ~
could spread across the equator, plunging sensitive tropi- spread uniformly and irlStantaneously over the Earth. Rath- ~
cal ecosystems and the naUons of the Southern Hemi- er than taking into account the oceans, which act dramati- ~
sphere into chilly twilight caUy to buffer any sudden climatic changes. separate com- ,
By blocking sunlight, the smoke would disrupt the puter runs had to be done for an all-water planet and an ~
transfer of radiation from the sun that creates and main- all-land planet {with 70 percent o1 Earth's surface being ~
tains Earth's equable climate. Most of the sun's energy is water, that is a large simplification). The simulations em- •
transmitted as visible light Sunlight penetrates the atmo- ployed a feature common to such models-a fixed sun- §
sphere and sbikes the continents and the oceans, which, that leaves out any possible effect of the daily cycle of light .~
t. varying extents, absorb the energy and heat up. The
o anddark. 3
66 SCJENCE DIGEST-MAACH 1985

6. Despite these and other assump-
tions, subsequent two- and three-di-
mensional computer analyses have,
for the most part. only mitigated the
effects described by TTAPS. Coastal
regions and islands would escape the
brunt of the deep freeze but might be
subjected to extraordinary storms as
the warmer air over the ocean clashed
with the cold air over land. Clear
patches in the canopy of smoke, low-
lying fogs and other factors would
lessen the effects. But only in a few
cases have simulations failed to show
significant, potentially destructive
cooling of the Earth's surface.
Mark Harwell, a Cornell biologist
who recently finished a book on the
subject, says, "You don't have to go to
the extreme bounds of any of these
ranges of uncertainties to be able to
generate a nuclear winter. Actually,
the converse is true. To come up with
a war that does not generate a nuclear
winter, you have to go to the ex-
tremes." Commenting on the critics of
TTAPS, he adds, "You can talk your-
self into saying, 'Gee, I could have a
nuclear war that didn't lead to nuclear
winter,' but it takes a lot of soft-shoe The atomk bomb thlrt the United Stlltes dropped on Hiroshima In 1945 tNid • yield of
16 kilotons, less than one pera!f1t of the powter ofsome of the smallest modem
routine. I've seen people do it" nudar WNponS. The resu~ flrestonn destro)<ed the city and raJsed a thld<, dartc
Here are some of the other findings pall of smoke. Witnesses thlrt the air grew cool and a ''black rain" feU.
that have appeared recently:
• Michael MacCracken, at Lawrence Livennore, ran a 11 of these global-scale models have major
three-dimensional global-circulation model (GCM) that
showed a 25-to-30-degree-Fahrenheit drop in average sur-
face temperature beneath the smoke cloud-half the
TTAPS finding, but still catastrophic by any estimation. A flaws, not the least of which is that they were
originally designed to study problems that are
tundamentaDy difierent from nuclear winter.
According to Bob Cess, at Stony Brook, many
• Vladimir Alexandrov, head of the climate research of the models were created to analyze the gradual, almost
laboratory of the USSR Academy of Sciences, using a dif- imperceptible buildup of carbon dioxide in the atmo-
ferent GCM and a 10,000-megaton war scenario, reported a sphere that may someday cause a runaway greenhouse ef.
temperature decrease similar to MacCracken's. · feet "Now we're using them for a vastly different thing," he
• Starley Thompson, Curt Covey and Stephen says. "We're going to have to start understanding how the
Schneider, at NCAR, running one of the most sophisticated models respond to a vezy large forcing-when you really
climate models available, got results that support some of hit the climate over the bead with a sledgehammer Instead
the TTAPS work, and they also observed a remarkable fea- of just barely tweaking it"
ture they called a quick freeze. The model produced patch- The models are also limited by the reliability of the data
es of freezing temperatures that migrated at random across that go into them. "U you have garbage in, then you've got
the globe as early as two days after a nuclear war. (TTAPS garbage out," Cess says. ''You start cascading the question
predicted the onset of freezing conditions after two or marks one on top of the other."
three weeks.) Richard Turco, the first Tin TTAPS, says the best we will
MacCracken says the NCAR fmding Oags a major weak- end up with is "a probabilistic picture of what could hap-
ness in almost all the studies that have been done so far. pen." Starley Thompson agrees: "If you knew every-
''What we should be looking at is not the change in cli- thing-what the initial meteorological conditions were the
mate-the average conditions-but the change In weath- moment the war started, where the bombs were going to
er, which is sho~-term, day-to-day fluctuations." A quick hit-in theory it's possible to have a model that would pre-
frost at the wrong time is all that is needed to destroy a did all the details of a nuclear winter. But all those things
year's cops. are essentially unknowable."
According to Schneider, the quick-freeze effect also At this point, most of the climate-modeling researchers
shows that input from the biologists is extremely important say one thing is dear. If enough smoke gets high enough,
to nuclear-winter studies. "You don't know what to gener- and stays there long enough, there will be significant sur-
ate from a physical model unless you're guided by what face cooling. But that is a big il Several questions remain,
matters to the biosphere." he says. "We might not have and they all concern smoke. How much is produced? How
looked for [quick frosts) if one of the biologists hadn't sug- high does it go? How long does it stay airborne?
gested it'' Conffnued
67

7. HARD FACTS clear what conditions lead to a firestorm
as opposed to a conflagration, which is a
mospheric scientist, burned Denver.
Fortunately for that mUe-high city, Cot·
large but unfocused blaze. ton did it on a Cray I supercomputer. He
The amount of smoke produced de- Kang, Michael Mac<:racken and others used a three-dimensional model that Colo-
pends first on the nature of the war. The doubt that proposed studies of experlmen· rado State researchers had designed to
range of possibilities Is Impressive-any tally set fires and accidental fires will bear study the behavior of powerful thunder·
number of combinations of "counter· much fruit. "The real problem," Mac· storms. As far as the atmosphere is con-
fOJCe" strikes. against military ~ts. and Cracken says. "is trying to scale lrom a reJ. cerned. be says. a nuclear explosion and
"countervalue" strikes, against industrial atively small fire-even a city block, for the resulting fires aeate a "convective dis-
assets. The only limit is the total number example-to what might happen If you turbance" that is not that different lrom a
of weapons available. Wlth the combined have a megaton explosion that sets nine- thunderstorm; they produce an immense
nuclear arsenals of the United States and ty-five square mUes or so on fire at the column of rising hot air. Cotton discov·
the Soviet Union containing 50,000 strate- same time. No one bas any idea how to do ered that almost balf of the smoke general·
gic and tactical weapons that is not much that" ed by the computerized flrestorm was
of a limit Once more, supercomputers come driven Into the stratosphere--where It
into play. Kang is piecing together a three- could reside for years instead of months.
"CUes Will Be Struck"
dimensional computer model of ul'ban· The model is a mathematical grid, 28.5
More specifically, smoke production de- fire behavior that he says is even more mlles square and divided vertically into 32
pends on how many dlies bum. OfticiaiJy, complex than many of the atmospheric slices, each 0.45 of a rnlle thick. It took
they are not targeted, but most defense ex· models. It will focus on the buUding-to- eight years to design, says its creator, Greg
perts assume that It would be impossible bulldlng spread of the names, a process Tripoli, and Includes more than 50,000
to light a nuclear war without hitting cities. that depends on things as subtle as the commands. Numbers are assigned to
Admiral Noel Gayler, now retired, has fate of win<kirlven firebrands-even the each grid point that represent the normal
been Commander U.S. Forces Pacific, dJ. layout of furnishings within buLidings. atmosphere; in this case, Cotton filled In
rector of the National Security Agency and "Given the same two-story wooden struc- the blanks with data that reflected the me-
deputy director of the Joint Strategic Tar· tures," he says, "If the fumlture Is placed teorological condJtions over Denver on a
get Planning Staff. In testimony last year at different ends. the fire history is going to particular day, June 4, 1983: Wind, tern·
before the Joint Economic Committee of be different" He foresees five years of ba- perature and humidity were entered for
Congress. he said. "Whatever the declara- each grid point at each altitude.
tive policy of either country, the weapons Then the bomb was dropped; the re-
that go after leadership, controL mllitary sulting firestorm was represented In the
capabiUty, industrial capability or eco- model by a huge flux of heat emanating
nomic recovery will hit cities. ... We must ''I'm sure a buming from a circular region five mlles aaoss.
face up to lt. Whatever our rhetoric or The temperatures were determined by es-
theirs, in a general nuclear war cities will New York City would timating how much fuel-wood, petro-
be struck, and they will bum."
The amount of smoke depends not
produce a different leum and the Uke--was available over
how large an area. Smoke production was
only on how many cities burn but on how kind of smoke than similarly estimated. The program respond-
well they bum. That dties can burn excep. ed to these "pertUrbations" and began to
tlooally well was amply demonstrated in a buming Moscow." churn out numbers. This Is what they add.
World War II. The Allies raised bumlng ed up to:
them to a science with a series of devastat· Vast gusts of hot air, rising 260 feet per
ing raids on German industry and popuJa. second, burst through the cool atmo-
tlon centers late in the war. sic research. sphere. Wate.t vapor in the updrafts con-
Early on the mornlng of February 14, The length of time the smoke stays m densed, creating a thunderstorm. The fire-
1945, the British Air Ministry announced the atmosphere depends In part on the storm and the newly spawned thunder·
that the German city of Dresden had been chemistry of the individual smoke part.i· storm combined forces to lift 1,400 tons of
attacked. Hundreds of 4,()()0. and 8,000- des. The nature of the particles affects the smoke into the upper atmosphere. Almost
pound bombs and more than 650,000 In- scavenging rate: Can they provide nuclei half of that made it into the stagnant,
cendiary devices were dropped in the first upon which water will condense? II so, weatheriess stratosphere.
wave of the assault The result was a fire- rainfall following a nuclear war could rap-
Compllalted Slmulattons
storm-a fire so fierce and hot that its up. idly clear the air. Do the particles stick to-
drafts sucked in air from all sides at near- gether when they coUide? Th.is process, The hypothetical blaze lasted less than an
hurricane force. Uke a beUows blowing on called coagulation, makes them fall to hour, but it took 10 hours of time o. the
n
a blacksmith's forge, the winds nourished Earth faster. And, according to Bob Cess, supercomputer-an indlcatlon of the
the Dames with fresh gusts of air, raising there is another factor to consider: "I grew complexity of the simulation. "It actually
temperatures thousands of degrees. up In western Oregon," he says, "where brought the Cray computer down to Lts
A British bomber pilot, one of the last we saw lots of forest·fire smoke in the knees a couple of times during the simula-
to fly over the dty that night. later recalled: summertime; It's very light stuff that looks tion because so much data was flowing in
"Th. re was a sea of lire. ... The heat strik·
e just like water clouds. But a refinery fire is and out." says Cotton. "We're right up at
ing up from the furnace below could be a totally different thing. And I'm sure a the top end of the technology we bave
felt in my cockpit ... The light inside the bumlng New York City would produce a available."
aircraft was that of an eerie autumn sun· different kind of smoke than a burning Cotton is careful to say that the results
set We were so aghast at the awesome Moscow. So there's no single smoke char· are preliminazy. The day he chose, June 4,
blaze that although alone over the dty, we acterlzatlon that's going to work in this was especially conducive to thunderstorm
flew around Ln a stand-off posiUon for business." The proposed federal research formation. and Denver is hardJy a typical
many minutes before turning for program includes laboratory Investiga- dty because of Its high altitude.
home. •.• We could still see the glare of tions of these questions. Since then, Bob Banta. a former col·
the holocaust thirty minutes after leaving." How high will the plumes of smoke league of Cotton's, has repeated the simu·
Several researchers are studying urban rise? According to a computer simulation latlon, using average weather condl·
fires, but this is an area with Uttle hard developed at Colorado State University, tion&-<:alled a standard sounding-for a
data. Sang-Wook Kang. a staff scientist at the smoke may go even higher than city at sea level. Banta, now a physical sd-
Lawrence Uvermore, says it isn't even TTAPS predicted. Wllllam Cotton, an at· Contfnu«< on PQ8t! 77
68 SCIENCE DIGEST-MARCH 1«;85

8. BUY ONE, ENJOY THREE
HARD FACTS sions. They have had no incentive to look
at global effects of multiple nuclear explo-
Ayres, who is now at Carnegie-Mellon
University, says a nuclear war will proba-
Continued from page 68 sions." As for why university researchers bly have some adverse climatic impact,
didn't catch on to the importance of but still thinks it unlikely that this ''would
enlist at Hanscom Air Force Base in Mas- smoke, he says, "You don't get brownie dominate over blast and radiation." Wl)en
sachusetts, says he got 22 percent of the points in academia for studying some· he reviewed the TTAPS report. he says, he
smoke into the stratosphere-half as thing as applied as nuclear war. You don't found only two paragraphs on what he
much as Cotton but still more than TIAPS. get promotion and tenure and things like considers to be the biggest question: the
The smoke is lofted so high so quickly, that So there's no incentive there either." possibility that most of the smoke wlll be
Banta says, that the scavenging processes scavenged by rain before it has a chance
HFull of Sloppy Work"
that normally remove particles from the to affect climate. "Frankly," Ayres says. ''I
atmosphere don't have time to work. "It's very strange," says Richard Turco. was somewhat dismayed that they
This work has been hailed as extreme- "When you look back through the litera- jumped to such dramatic conclusions."
ly important by many in the nuclear-winter ture, which mainly consists of the 'gray' lit· In 1966, Edmund Batten, working for
research community. Even so, Cotton's erature-reports and things of that sort- the Rand Corporation, produced a report
paper was rejected last fall by Science. you can literally pick up a handful of re- titled "The Effects of Nuclear War on the
·There is one more question, perhaps ports that have addressed these possible Weather and Climate" for the Atomic En-
the biggest one of all, that concerns long-term consequences of using nuclear ergy Commission. He mentioned smoke,
smoke: How could the significance of weapons in large numbers. And those are but only smoke from forest fires. As an ex-
smoke, the cornerstone of such an enor- not very authoritative, are fuJI of very slop- ample, he referred to a massive fire that
mous, il putative, environmental cata- py work and aren't very imaginative. And burned 3,800 square miles in western Can-
clysm, stay hidden for so long? At a con- you have to wonder why that is. I think ada. Among-its effects, "the pall of smoke
gressional hearing last summer, Richard one reason is everybody always assumed from the 1950 Alberta fire was believed re-
Wagner, Jr., Assistant to the Secretary of that It's going to be such a disaster an-jway sponsible for reducing the incoming [so-
Defense (Atomic Energy), testified, "Not that 'who cares?' " lar] radiation by fifty-four percent and low-
only the Department of Defense but the In 1962, Robert Ayres, then at the Hud- ering the temperature ten degrees
scientific community in general ought to son Institute, undertook a three-year study Fahrenheit at Washington, D.C."
be a bit chagrined at not realizing that of the environmental effects of nuclear Despite that startling finding, he con·
smoke could produce these effects." war for the Office of Civil Defense (now eluded that "these short-term effects are
John Birks, one of the authors of the absorbed by the Federal Emergency Man- not expected to last for more than a few
Ambio study. offers two answers: "De· agement Agency, FEMA). He realized that weeks."
tense scientists, who are the ones funded smoke could have an effect on climate. Starley Thompson recently came
to look at this, are not attuned to this sort But because he was working alone, "with across the Batten study. "Now that I find
of thing. Their job is to build weapons to no computers or fancy mathematical out that people actually thought about
prevent war. Their work has focused on models," he did not try to calculate specif- smoke as long as eighteen years ago," he
prompt effects of single nuclear explo- ic consequences. Continued on page 81
77

9. HARD FACTS stratosphere where they can destroy
ozone.
Continued from page 77 So the two scientists turned their atten-
tion to the troposphere, the lowest six
says, " it surprises me more and more that miles or so of the atmosphere, to see what
somebody didn't draw the connection effect the nitrogen oxides would have
more strongly. Batten himself tended to ig- there. One ingredien~ in a postwar atmo-
nore it in favor of dust If somebody with sphere would be smoke. In the presence
radiative transfer experience had read that of sunlight, the nitrogen oxides would re-
paragraph, they would have probably hit act with compounds in the smoke, a pro-
upon (nudear winter] eighteen years ago." cess that produces ozone-just the oppo-
The Office of Civil Defense funded yet site of what would happen in the
another study in the 1960s that seemed to stratosphere. Ozone at the Earth's surface
miss the mark. "Project flambeau, an In- is toxic to many plants and a major com-
vestigation of Mass Fire," was a three-year ponent of smog.
effort to simulate intensive urban fires and But, recalls Birks, they reasoned that
study their behavior. According to a report the same smoke that would contribute to
by Clive Countryman, the project's first di· smog formation might also cut back on
rector, mock city blocks were constructed the amount of sunlight, and that could lim-
by laying out grids of up to 324 " houses," it the production ol noxious ozone. They
each a square stack of 20 tons of pinyon still didn't realize what they were working
pine and juniper, 46 feet on a side and toward, but they were getting dose.
about 7 feet tall. Instruments of every de- To measure the reduction in sunlight,
scription were strung around, above and Crut. en and Birks needed to estimate
z
within the firebed. The flres were set with smoke production and did so using data
simultaneously ignited pouches of jellied gleaned from studies of forest fires. It ap-
diesel fuel Smoke partides were trapped, peared that several hundred mUllon tons
temperatures (up to 3,000 degrees Fabr· of smoke could be lofted into the atmo-
enbeit in some cases) were measured, sphere. "We found out that easily some-
winds were docked. Thousands of pages thing like ninety-nine percent of the sun-
of data and thousands of feet of film were light could be blocked," says Birks.
collected-and almost nothing was done Suddenly, ozone became a side issue.
with it With less than three months to go before
their deadline for the artide, Crutzen and
Funding for Research CUt
Birks completely changed focus. The title
Around 1970, most of the funding for the they chose reflected the new findings:
Office of Civil Defense was cut, and that "The Atmosphere After a Nuclear War:
was just about the only agency requesting Twilight at Noon."
this type of research. The TIAPS group was uniquely quali-
For more than a decade, nothing hap- fied to take over where Crutzen and Birks
pened. And, according to John Birks, left oH. Their experience with the effects of
when he and Paul Crutzen finally realized aerosols-particles suspended In the
that smoke could obscure the sun. It oc· air-went all the way back to 1971. Carl
curred to them purely by chance. Sagan was involved with the Mariner 9
Buts. a chemistry professor at the Uni- mission to Mars. The probe arrived at
versity of Colorado, went on sabbatical in Mars to find the planet engulfed in a global
1981 to study computer modeling with dust storm--a common occurrence, ac-
Paul Crutzen, a director of the Max Planck cording to Sagan-that lasted three
Institute for Chemistry in West Germany. months. While the scientists back on Earth
Around that time, Crutzen received an in- were waiting for the storm to dear, they
vitation to contribute a section on the at· had the probe take temperature readings
mosphere to a special issue of Ambio, of the atmosphere and the surface. They
which is published by the Royal Swedish noted that the atmosphere got warmer, ap-
Academy of Sciences, on the human and
ecological consequences of nudear war.
Because Birks had previously worked on
the effects of nudear explosions on the
parently because the suspended dust ab-
sorbed the sun's energy, while the surface
grew cooler. Once the dust settled, condi-
tions reverted to the norm-warmer sur-
-- ---,
IHeathklt·5..~.. - 1
ozone layer, the two scientists decided to face and cooler, dear atmosphere.
1
collaborate. Since 1975, it had been as-
sumed that the major atmospheric pertur·
Comparing Mars and Earth I'Sendnot currently receiving yournow.
am
my ' ' " Heathkit Catalog
catalog.
1
1
bation produced by nudear war would be In 1976, Sagan, Brian Toon and James Pol- I I
severe depletion of the layer of ozone high lack published a paper in which they com- I Name ~
in the stratosphere that prevents harmful pared the Martian observations with
quantities of ultraviolet radiation from events on Earth, specifically climate I Address I
reaching the Earth. changes following volcanic eruptions. I City State --1
l:::~----~-----1
Crutzen and Birks chose the ozone A well-documented example was the
problem as a natural starting point But. 1815 eruption of Tambora in what is now
says Birks, things had changed since 1975. the Indonesian archipelago. The year that
Warbeads had become smaller as accura-
cy improved. Warheads of less than half a
megaton are not powerful enough to in·
followed that catadysm, which blew off
the top 4,000 feet of the conical mountain,
was later referred to in New England and
• Heathkit•
Heath
ject nitrogen oxides, compounds created Europe as "Eighteen-Hundred-and-Froze- Company
in the thermonudear fireballs, into the Continued on page 83
81

10. what they like, whereas we tell our people
HARDFACI"S what Sagan likes."
Continued from page 81 Despite his public denunciations of the
TTAPS group, Teller has conceded in con-
to-Death" and "the year without a sum· gressional testimony that a nuclear war
mer." Crops failed across both conti· could have significant climatic effects. He
nents--and that was the result of a drop in has also proposed contingency measures
average tempe. ature of only 1.8 degrees
r that he says would lessen the impact For
Fahrenheit example, Teller says, "we should increase
In 1980, another catastrophic event, our food storage, which is for us very easy
the extinction of the dinosaurs, had been and for others possible." He has even ten-
tentative. y linked to a wayward asteroid
l tatively discussed the idea of firing rockets
that may have collided with Earth 65 mil· into the atmosphere filled with micron·
lion years ago, blasting vast quantities of size needles that "resonate with the infra.
fine dust into the atmosphere. Toon and red, but which let visible light through,"
Pollack joined forces with Richard Turco thus countering the nuclear-winter effect
and calculated that the collision might by keeping in the escaping heat
have created a period of prolonged cold
A Kind of Weather Lottery
and darkness. The seeds for TTAPS were
sown. All that was needed was the nuclear Richard Turco has labeled these respons-
connection and the link to smoke. The for- es "absurd." He describes a similar mind-
mer was provided when Turco and Toon set he has seen among other members of
were asked by the National Academy of the defense community: ··one guy said,
Sciences to contribute to a massive study 'Well, if it gets ten degrees colder we'll just
on the effects of nuclear war. The latter, of grow the com in Mississippi, move the
course, was provided by Crutzen and com belt down.' Well, that's fine if you just
Birks. Finally, Turco, Toon and Pollack had these nice temperature contours and It life jutt a haphazard phe-
were joined by Sagan and Thomas Acker· you could figure out where exactly the eli· nomenon? Are there but blind
man, a computer expert at the NASA malic situation is going to be good for mechanistic laws, causes and ef-
Ames Research Center, and TTAPS was com. But that's not the way it's going to
born. Says Turco, "We just sort of synthe- work. It's kind of a weather lotterv or rou· fects without purpose? Is there a
sized information from a large number of Jette that you can never resolve. Also, no- reason for our personal existence?
areas and combined that with understand· body's ever used these weapons, so we Can we establish a personal mis-
ing how the climate works. The informa- really can't predict what's going to happen sion that will be in harmony with
tion was sitting there; it just needed to be anyway." Infinite Reality-or must we drift
gathered and tied into a package." Freeman Dyson says nuclear winter is
a positive thing, "because it is a powerful along , buffeted by the winds of
The Fate of the Theory chance? These are subjects fasci-
political force against nuclear weapons. It
The fate of the nuclear-winter theory will is dramatic and beautiful." But Dyson sees natingly explored by The Rosicru-
not be decided in anything approaching a a darker side to this nascent theory. "It is cians, a worldwide fraternity. Ask
definitive way for at least three years, ac- somewhat analogous to what Unus Pau- for a free copy of the book. The
cording to most of the researchers que- ling did in the 1950s when he fought
ried. Even then, there will only be a reduc- against nuclear weapons on the fallout is- Mattery of Life.
tion of probability, a closing in on a sue," be says. The public became educat·
plausible course of events-nothing com- ed to the dangers, but "unfortunately, the
pletely definitive. atmospheric test ban treaty carne along
The Rosicrucians are:
In spite of the potentially enormous and got rid of the fallout without getting rid • Not a religion
ramifications of nuclear winter, there are of the testing." Dyson says the danger now • Nonprofit
those who doubt it will affect public poli- is that the military response to nuclear • Nonpolitical
cy. Robert Ayres, at Carnegie-Mellon, says winter, if research tends to support it, may
that Sagan may have damaged his scientif- be to "get around it in a technical fashion
ic credibility by discussing the political im· . ... Change targeting doctrine and de- USE THIS COUPON
plications before the validity of the theory ployment, produce only warheads of less r-----
1 i
is confirmed. In his contribution to TTAPS than a hundred kilotons and the thing Scribe ESM I
critic Fred Singer's forthcoming book goes away-just like fallout" Rosicrucian Order (AMORC) I
I
about nuclear winter, Ayres says, "The Rosicrucian Park
transparency of Sagan's motives may
Uncertainty Is Desirable San Jose, CA 95191 , U.S.A. I
I
have detracted from the effectiveness of But Dyson, Schneider, Sagan and others I
his argument .. . The nuclear hard-liners still say the final effect will be positive: The 1 Gentlemen: I
~ KlndlyMndmeefrMcopyofTHEMA$- 1
in the Reagan Administration will be ultra·
suspicious of any conclusions based on
very uncertainty that plagues research intt~ TERY OF LIFE. l
the phenomenon is desirable. Schneider
mathematical models that are not com· says, "A lot of the young guys who work
pletely and fully tested and verified. They with me ask, 'Is there any chance that l ::;r:..-_-_---_-_-:_-_-_-_--_-_-_-_-_---
__ _ -1
will point out, correctly, that it would be could make war more probable by these
doubly disastrous if the U.S. leadership be- studies?' And the answer is there's always
lieved in the Sagan thesis while the Soviet a chance. But the only way you make war zip I
leadership did not." more probable is by giving one :;ide the 1
He is echoed by Edward Teller, who belief it has a distinCt advantage it didn't
has been playing devil's advocate to the used to have." The Rosicrucians (AMORC)
TTAPS group for more than a year. "My According to Dyson, "the ideal an-
main worry is that [nuclear winter] may be swer" to the nuclear-winter question will S.n JOH, Cellfomle 95191 , U.S.A.
exploited as a propaganda point by the So- be, ·• 'Yes, this may happen, and there's no
viets," Teller says. "They tell their people way we can ever tell.'" •
83