The science of Nuclear Winter


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19 December 2006
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All Right; Please try not to turn this one into a flamefest like the last one guys. :eek:

A long time ago, on a message board many changes ago (it's gone now due to server failure wiping out teh board) asked the following question:

A Poster said:
I remeber throughout the years hearing about nuclear winter and then I find out that the explosion of several volcanoes, Tamboro I believe is one, have dwarved the energy of every nuclear weapon in the height of the cold war. This has lead me to think that the entire concept of nuclear winter is bunk although I don't know what effects radiation would have. What are others opinions on this?

Stuart Slade, a military analyst at Forecast International up in Connecticut, and also author of several articles on NavWeaps

NavWeaps Technical Article Board
Stuart's Bio on NavWeaps

BTW, as a slight aside, he actually did work on a Secret Project (TM).

Type 43 on Secret Projects

Most of his work on T43 was concerned with anti fouling paint for the hull and the effects of flow on the paint.

Anyway, I digress; back on topic; Stuart had this to say about Nuclear Winter:

Stuart Slade said:
Bunk is a pretty fair description.

The "nuclear winter" theory was predicated on a series of hypothetical models that had been constructed by a group of "concerned scientists" led by Carl Sagan who constructed a computerized model of earth, cranked in a series of hypothetical statistics on the effects of nuclear weapons and then claimed that the results from that model constituted "facts".

There were a number of serious problems with this process.

One of them was that, when the hypothetical effects of nuclear initiations were cranked into other models of earth, they didn't produce the results Sagan had reported.

In fact, the results reported by Sagan's group were only achieved when his particular model of the earth was used. This was a remarkable thing so people looked at Sagan's model to see how it differed from the rest. The answer turned out to be quite simple. The model Sagan had shown to the world press to “prove” the danger of “nuclear winter,” depicted the earth as being a barren ball of rock with no mountains and no oceans. Oceans, as Sagan well knew, act as gigantic energy flywheels that moderate temperature, helping cool adjacent continents in summer and warm them in winter.

Sagan, in other words, knowingly committed deliberate scientific fraud. He cooked up a phony computer model to concoct the phony “nuclear winter” results he wanted for political reasons. It subsequently became apparent that he had avoided using the already-available NCAR computer climate model precisely because he knew it would not produce the “nuclear winter” he wanted to sell to gullible journalists and an ignorant public.

Once that point had been realized, Sagan's assumptions were examined in greater depth. It turned out that none of the people in his group of "concerned scientists" were nuclear weapons experts. What they'd done was taken some generalist public sources, cherry-picked the ones that suited them and used them without examining how the various nuclear weapons effects interacted. Again, there was a healthy dollop of deliberate scientific fraud here. Where effects didn't give the results required, they were exagerrated or morphed until they did. By the time the critique was over, "nuclear winter" as a concept was totally discredited; today its a touchstone.

If somebody starts to spout forth on the dangers of "nuclear winter" they're nutcases. Sagan's credibility never recovered; he never got another hearing from the serious nuclear weapons and policy community.

However, one useful thing did come out of all this. In order to examine the probability of Sagan's fairy stories, people cranked real data on nuclear weapons into real atmospheric models. The results were actually quite interesting (there is a novel currently being posted in HPCA called "Anvil of Necessity" which draws on that work).

For those who like grim details, the following was the nuclear exchange used as a basis for these studies.

The US was presumed to have been hit by 5,800 warheads witha total yield of 3,900 megatons. Nuclear devices initiated in Europe totalled 3,300 with a total yield of 1,200 megatons The USSR was deemed to have been hit by 6,100 devices having a total yield of 1,900 megatons. China got hit by 900 devices witha total yield of 1,300 megatons. By way of comparison in TBO, Germany got hit by 232 devices totalling 8.6 megatons.

Other areas receiving at least a dozen warheads include Canada, North and South Korea, Japan, Taiwan, Greenland, Puerto Rico, India, Israel, Australia, Guam, Cuba, Syria, and Egypt. Other countries got single devices, mostly on their capitals.

Nobody didn't get hit by something.

This massive exchange used about half the global strategic and theater nuclear arsenal; about 10% was launched but did not reach a target and 30% was destroyed on the ground.

By the time we finished there were 10,000 nuclear weapons left in the arsenals out of the 67,000 that we started with.

Initial casualties were 400 million dead; by the time things had worked out, this increased to 1.2 billion.

Welcome to my world.

The smoke clouds from the fires etc peak three days after the exchange. Essentially, they would spread to form a doughnut shaped band around the world that would essentially cover North America, Europe and the USSR.

This smoke (actually, its particulates rather than smoke) cloud consisted of 1,500 million tons of dust, 25 million tons of smoke from vegetation, and 80 million tons of smoke from cities and other manmade sources. It is very important to note that the last type of smoke has the greatest impact: smoke from petroleum and petroleum products is particularly effective at absorbing sunlight. Altogether, about 0.4 cubic km (0.1 cu. mi.) of dust and smoke is in the stratosphere.

The general effect (and this is the peak remember) would be to reduce sunlight intensity and temperature by a degree comparable to an overcast day. That's a general comment, if the observer is downwind of a stricken target, the intense plume from the smoke generated by large continuing fires will reduced mid-day light levels to that of twilight. The average peak temperature will be reduced by around 13 degrees F.

However, there is a peculiar effect here; average trough temperatures will be increased by roughly the same amount (for exactly the same reason that a cloudy night is warmer than a clear one; the smoke clouds also tend to hold warm air in. That was an effect that Sagan and his crew deliberately suppressed.

Within ten days, the smoke/particulate concentration would decline rapidly although smoke in the upper atmosphere still absorbs much sunlight. The primary effect ceased to become temperature and the gross temperature changes would already be a thing of the past. Instead, the patchyness of the initiation effects would cause unusual weather conditions including strong winds in some coastal areas (in effect we've dumped huge amounts of energy into the climatoscene and that starts to work its way out).

A curious predictable phenomena is that dense fogs would develop over the oceans and along waterways. Another interesting effect is that the ozone layer would be reduced by nearly half yet nearly all of the Earth's surface would receive less solar ultraviolet radiation than before the war. The reason is curious; although smoke levels would be dropping rapidly, there would now be a thin veil of very fine high altitude particulates that effectively act as a block to UV radiation.

The sunsets will be incredibly beautiful.

Twenty days after the nuclear exchange climatic effects would have peaked. By this time, areas alongside seas, oceans and other large bodies of water would have effectively returned to their pre-exchange temperature sets. High-altitude areas woudl actually be warmer than before the exchange, sometimes dramatically so. At an altitude of 40,000 feet, the air termperature would be no less than 70 degrees F higher than normal (!!!)

Surface temperatures far inland will drop by around 20 degrees F but this is a transient phenomena.

The critical thing is light level; although the veil of fine high-altitude dust doesn't have a critical temperature effect, it cuts light levels by around 25 percent, ensuring that crops fail.

Within three months, temperature effects are virtually over. Worldwide, peak temperatures will have been reduced by, at most, 2 degrees F while trough will be increased by the same amount.

This will shorten crop growing seasons a bit but since the crops are failing anyway it won't make much difference. This temperature change will persist for two or three years. by which time the atmosphere will have been purged of dust and smoke.

The best way to describe the real climate change would be that a state of "nuclear autumn" would become widespread. In other words both the high and low ends of the temperature spectrum would be shaved so that things tend to the "median" situation.

Now, as much as I know Stuart; as Reagan used to say, "Trust but Verify"; I found this passage in a book:

The Strategic Nuclear Balance: Exchanges and Outcomes? by Peter Vincent Pry, Page 202:

Subsequent analyses of TTAPS have not supported its findings. Russell Seitz, of Harvard University's Center for International Affairs (and formerly with the geophysics division of C. S. Draper Laboratory), has traced the history of nuclear winter research and found that the trend has been, as climatological models have improved, to predict less severe nuclear winter effects and finally to discredit the phenomenon (see Figure 7.1). Seitz describes some of the erroneous assumptions in TTAPS that were corrected by later studies:

Because so much depended on them, the assumptions embodied in the TTAPS software merit a closer look. Instead of a planet with continents and oceans, the TTAPS model postulated a featureless bone-dry billiard ball. Instead of nights and days, it postulated twenty-four hour sunlight at one-third strength. Instead of realistic smoke emissions, it simply dumped a ten-mile thick soot cloud into the atmosphere instantly. The model dealt with such complications as east, west, winds, sunrise, sunset, and patchy clouds in a stunningly elegant manner—they were ignored. When later computer models incorporated these real-world elements, the flat black sky of TTAPS fell apart into a pale broken shadow that traveled less far and dissipated more quickly. One factor alone— the moderating effect of the oceans—turned out to be the source of a 200 percent error.

The book I believe, printed this image as Figure 7.1 The decline and fall of "nuclear winter."


Attributed as being from Russell Seitz, "In From the Cold: Nuclear Winter Melts Down," The National Interest (Fall 1986), p. 8.

with the following quote

The figure shows how successive studies of nuclear winter have sharply revised downward its estimated severity, as expressed in the number of "heating degree days" that would result. "Heating degree days" are computed by multiplying how far temperatures drop below 65° F by how many days the lower temperatures last. For example, two days having temperatures of 60 degrees would account for 10 "degree days." As Seitz puts it: "The contrast between the original 22,000-degree-day catastrophe-equivalent to a year and a half of Alaskan winter-and the final few-degree-day cool spell is clearly apparent." The figure also shows that, despite the discrediting of nuclear winter by the scientific community, the popular press incorrectly kept revising upward the mortality estimates associated with nuclear winter. The best evidence suggests that nuclear winter would not occur and that no one would die from brief episodes of cool weather that might attend a counter-force nuclear winter.
You can compare with data from the effects of some volcanic eruptions:



the latter could give reason to believe that since the effects of Pinatubo were predicted, the global circulation models were somewhat up to speed by the beginning of the nineties.
actual studies

Michael Mills and Owen B. Toon from University of Colorado
made simulation of small Nuclear war between India and Pakistan and this Nuclear winter
100 nukes with 15 kt (1.5 MT) would produce five million tonnes of dirt into the air
In large parts of North America and Eurasia, the temperature by several degrees,
In the affected regions was also the biggest part of the grain-growing areas.
Even in the world, far from the place of nuclear war, there would be major climatic consequences.
That of a regional nuclear war could take up to ten years !

and also this as "ultraviolet Spring" described phenomenon

the mushroom cloud raise up to 15 - 50 km high
in ozonlaver the temperature rise around 30 to 60 degree !
In the middle latitudes, according to scientists, a loss of up to 40 percent of ozone are expected
This decrease in the ozone layer varies according to latitude, but for three years, the average global shift to the level of today's Antarctic ozone hole to fall.

From sunlight caused damage in plants would according to the calculations
132 percent increase, people would have an increase of 213 percent for DNA damage can be expected.

and this only with 1.5 MT
a nuclear war in 1960s (Cuba crisis gone mad) had be around 1500-2000MT
while a nuclear war in 1980s had be 5000 to 10000 Megatons

German news on-line magazines "Der Spiegel",00.html,00.html

Massive global ozone loss predicted following regional nuclear conflict by O. B. Toon

Atmospheric effects and societal consequences of regional scale nuclear conflicts
and acts of individual nuclear terrorism by O. B. Toon

Climatic consequences of regional nuclear conflicts by O. B. Toon
I think Stuart's piece actually demonstrates a misconception about science, that is that scientists have a complete knowledge of the fields that they study. This isn't true - this is why experiments are performed to gain knowledge of the field in question. Usually basic experiments (and you can include modeling in this) are performed at the start of research into a field of knowledge, in order to gain some basic knowledge. This makes it preposterous to accuse Carl Sagan of "scientific fraud" for using a simplistic model to initially investigate the 'Nuclear Winter' hypothesis. In fact, Carl Sagan even admitted to the basic nature of his initial model saying:

"The TTAPS study has the important limitation that it is dependent on the one-dimensional radiative convective model ... what is clearly needed is a high spatial resolution, fully interactive, three-dimensional model." "Nuclear war and climatic change — Guest editorial", Climatic Change, Volume 6, Number 1 - March, 1984

Hardly the words of a fraud.

On the subject of Nuclear Winter itself, from what I can glean on Google Scholar, it is still an active area of research. Sadly, many of the papers are hidden behind paywalls - making it difficult for me to appraise the current state of the art. One which is available is:

"<a href="">Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences</a>" Robock, Oman, and Stenchikov, <i>Journal of Geophysical Research</i>, Vol. 112 - 2007

Their model is an atmosphere-ocean general circulation model, and they state:

"A global average surface cooling of -7°C to -8°C persists for years, and after a decade the cooling is still -4°C. Considering that the global average cooling at the depth of the last ice age 18,000 yr ago was about -5°C, this would be a climate change unprecedented in speed and amplitude in the history of the human race. The temperature changes are largest over land ... Cooling of more than -20°C occurs over large areas of North America and of more than -30°C over much of Eurasia, including all agricultural regions."

In finishing, I'll note that I'm disappointed that Stuart's piece seems to have no scientific information past 1986 - essentially it's 23 years out of date. Also his tone is revealing: "concerned scientists", "facts", scientific fraud, phony, nutcases - hardly the dispassionate reporting needed in matters scientific.
Thank you for the links Michael Van, I know what I'll be reading through today! (your link to produced a lot of readable PDFs)
RyanCrierie said:
Thank you for the links Michael Van, I know what I'll be reading through today! (your link to produced a lot of readable PDFs)

was a pleasure to help

back to Starviking remark on TTAPS

its almost a fraud.
TTAPS was first study on Nuclear Winter hypothesis.
Carl Sagan and his team used Wat they could get
a one-dimensional radiative convective model ... of Atmosphere of planet MARS
and even that was Killer application for 1980s "Supercomputers"

later new study of Robock, Oman, Stenchikov and work of Mills and Toon
used three-dimensional model.

TTAPS major point was, it make clear that nuclear War. Can be not survivable !
Wat start a think process at Politicians in 1980s
Michel Van said:
back to Starviking remark on TTAPS

its almost a fraud.
TTAPS was first study on Nuclear Winter hypothesis.
Carl Sagan and his team used Wat they could get
a one-dimensional radiative convective model ... of Atmosphere of planet MARS
and even that was Killer application for 1980s "Supercomputers"

later new study of Robock, Oman, Stenchikov and work of Mills and Toon
used three-dimensional model.

"Almost a fraud" could be misconstrued - basic is the word I'd use ;)

(That said, a lot of stuff has been done with basic equipment!)

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