How Many Nukes Does it Take to Trigger Nuclear Winter?

Apr 2017
1,640
U.S.A.
I've seen several videos that state it would only take a few hundred nuclear weapons to trigger a nuclear winter, others say far fewer. Another video stated that scientists feared a small nuclear winter from the burning oil fields of the gulf war (which obviously didn't happen). If it would only take a hundred nukes to do it, then wouldn't their have been noticeable effects from all the nuclear testing of the cold war?
 
Mar 2018
795
UK
The most honest answer is nobody knows. Atmospheric physics is hard even when dealing with normal stuff, nukes add so many unknowns any prediction is little more than guess work. I imagine where they are matters as much as the kilotons, the dust thrown up into the upper atmosphere would have a major impact (as with volcanoes).
 

AlpinLuke

Forum Staff
Oct 2011
27,051
Italy, Lago Maggiore
The most honest answer is nobody knows. Atmospheric physics is hard even when dealing with normal stuff, nukes add so many unknowns any prediction is little more than guess work. I imagine where they are matters as much as the kilotons, the dust thrown up into the upper atmosphere would have a major impact (as with volcanoes).
That's quite correct. Overall, like for the impact of a big asteroid, also where the nukes explode [above the oceans, the inland ... where?] changes the model to elaborate. Since modern nukes are programmed to explode at about 0.5km above the surface [let's use this data available on the net, without knowing the level of reliability, anyway it's a reference], it's evident that if a nuke explodes above the ocean [to destroy an important naval base along the coasts of an isle, for example] the mushroom will attract overall water vapor [which is a green-house gas], not concrete fragments of soil [considering the temperature ... ash ...]. So, to make it clear: a nuclear war against Japan would have less probabilities to generate a global nuclear winter than a nuclear war against Russia, US or China. More continental is the target, more probabilities of a nuclear winter there will be.
 

Todd Feinman

Ad Honorem
Oct 2013
6,519
Planet Nine, Oregon
Nuclear Winter: Uncertainties Surround the Long-Term Effects of Nuclear War

Nuclear Winter: The State of the Science - The Medical Implications of Nuclear War - NCBI Bookshelf
"In the National Research Council's recent report, The Effects on the Atmosphere of a Major Nuclear Exchange, a particular scenario for a nuclear exchange in which somewhat less than half (6,500 megatons) of the world's arsenal is expended was adopted as a baseline case. In other words, this scenario was used to illustrate the process of estimating the atmospheric effects of a nuclear exchange. No pretense is made that this is a "most likely exchange." It is merely a plausible assumption whose estimated consequences can give some guidance regarding possible atmospheric degradation. For this assumed nuclear exchange, the amount of submicron smoke that would survive the ascent in the fire plume is between 20 million tons and 650 million tons. These numbers are generally consistent with the uncertainty factors given above. (Some small and unimportant discrepancies arise, however, because this discussion is a highly simplified recasting of the National Research Council's report.) In that report, for purposes of inquiry, the investigators chose to assume that 180 million tons of submicron smoke were injected at altitude (four to nine kilometers) in the atmosphere."

NASA - How Would Nuclear War Affect The Climate?
 
Apr 2017
1,640
U.S.A.
The gist I got from the article is a hundred large nukes exploding over cities would trigger a survivable nuclear winter but still a devastating one.
 
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Jun 2019
61
St.Petersburg
Nuclear winter can be caused not by nuclear explosions itself, but massive fires, caused by large cities bombing. Nuclear testing were mostly underground, and so didn't produce large air emission.