# How big could a nuclear war be without causing an apocalypse?

It is widely known that an all out nuclear weapon with modern nuclear missiles would probably cause a nuclear winter, billions of deaths, and end life as we know it.

On the other hand, two small (by modern standards) A-bombs dropped on Japan in 1945, while causing hundreds of thousands of deaths in an instant, did not end life as we know it, and even Japan went on to recover and thrive as a world power within decades afterwards.

How large could the scale of a nuclear war that did not end life as we know it, and did not render more than a city sized area uninhabitable for more than a decade be?

• WW2 was a very large war. It is the only war in which atomic bombs were used. And it did not render any area unimhabitable for a decade. On the other hand, WW1 was also a very large war; although no atomic bombs were used, areas much larger than a city were rendered uninhabitable for quite a long time. Mar 19, 2022 at 0:31
• "This question is answerable at some approximate order of magnitude": and order of magnitude of what? What is the metric? I have no idea how to measure the bigness of a war. Mar 19, 2022 at 0:32
• But the question does not ask how many strikes, not does it ask how many megatons. It asks how big a war. Strikes and megatons are easy: the Americans, the British, the French and the Russians detonated many atomic bombs during the 1950s and 1960s, so you can easily count them and add up the amount of energy released to get a baseline number of strikes and megatons which very obviously did not cause a nuclear winter. (You will be surprised how many bombs and total megatons those four civilized nations detonated. You can definitely have a reasonably large war.) Mar 19, 2022 at 0:51
• This was a fairly easy question to answer, since lots of people online have asked how big a nuclear has to be to cause a nuclear winter. Mar 19, 2022 at 1:04
• Your assumptions are entirely based on unsubstantiated conjecture. Consider it would take over 100 of the most modern nukes to completely destroy just the main area of the City of New York, and the effects would not even reach Pennsylvania, the answer is 'a conflagration at least 50 times greater than the combined might of every nuclear power currently on Earth today'. There would be no 'nuclear winter' with just today's number of nukes. Mar 19, 2022 at 3:54

Between 1945 and 1963 there were more than 400[*] nuclear explosions in the atmosphere. Since they were spread over a period of 15/18 years there was time for some dust to settle, their effect was not fully cumulative. Except for 1962, US and Russia wanted to test as much as they could before the ban of atmospheric testing went into effect and they conducted more than 100 tests in a single year, furthermore the big number of tests of 1962 was preceded by the big and inefficient tsar bomba in 1961.

So, since we are still alive and experienced no nuclear winter you can assume that more than 100 explosions are still within the safe threshold. Then it depends on what type of bombs could be used. Modern thermonuclear bombs would have a devastating effect, but would produce less waste, the bombs with the smallest amount of toxic by-product would be one based on the fusion of tritium, but since tritium is difficult to produce and has a short half life the number of available bombs would be limited. Anyway a lot will depend on the type and technology of the weapons, but with modern technology you can expect a conservative threshold over 200 bombs if the war happens in a very short period of time like could be an exchange of ICBM between two powers. If the war is fought over a prolonged period the threshold might be higher.

# It depends on what they hit, but 100 good strikes.

Hiroshoma was especially bad not just because there was a big boom, but because the city burned down. The burning down of hiroshima released 1000 times more energy than the actual nuke.

Assuming they all hit cities, and cause a similar amount of burning, 100 cities burnt to ashes should be enough.

It's also dependent on rain. If there's heavy raining around the time of the nuking, that might reduce the amount of ash sent up.

• So, for example, ten strikes might not lead to nuclear winter, at least if the conditions in the places where the strikes occurred were right. Mar 19, 2022 at 0:32
• Yeah. If there was heavy rain, or if it was on a military location where there was little material to burn, it might not produce much global warming. Mar 19, 2022 at 0:33
• @NepeneNep Exactly. It depends on weather and location and some other things, like building density. That is why you would have to consider 1000 scenarios with 100's of different parameters to answer this.. and you won't be able to calculate it, like Wiki seems to do. Putting "100 strikes" as answer is completely arbitrary. Wiki sais "the ignition of 100 firestorms, each comparable in intensity to that observed in Hiroshima in 1945, could produce a "small" nuclear winter" but without any precise data about where the nukes landed and how much dust was released. Issue: you don't know. Mar 19, 2022 at 0:48
• It requires certain amount of combustibles per square meter to get a firestorm going as determined via study/investigation of bombing of German cities. Most modern cities do not have that amount of combustibles. So huge fires won't be a thing for most cities. Limited fires yes, massive city consuming firestorms, no. Mar 19, 2022 at 1:48
• 50,000 nukes would not cause a Nuclear Winter. The surface area of the world is just too big. 50,000 nukes would be like a bug hitting a car windshield. Just look at the miniscule damage hundreds of cruise missiles did in Syria. Compared to a nuke, the Earth is HUGE Mar 19, 2022 at 4:03

You actually do not need to cause nearly as much destruction in order to devastate the modern world through the use of nuclear weapons. Nuclear winter is caused by the fine particulate dust which is kicked up from the explosion. That increased dust in the upper atmosphere blocks incoming sunlight. The destruction of cities is not really needed to cause havoc. It makes for a scary image on TV, but is less effective than exploding nuclear weapons to create high-altitude electromagnetic pulses. “A nuclear detonation in the upper atmosphere creates an electromagnetic pulse (EMP), a powerful, damaging electromagnetic field covering a subcontinent-scale region.” (https://eiscouncil.org/emp-high-altitude-electromagnetic-pulse/)

“The detonation of a nuclear weapon at an altitude of approximately 500 kilometers over the United States will generate a near-continental scale high altitude electromagnetic pulse (HEMP). The effects of such an attack may instantaneously destroy or disrupt substantial portions of the electrical and electronic systems that operate the critical infrastructure of the United States, as well as portions of Canada and Mexico.” (https://apps.dtic.mil/sti/pdfs/ADA424218.pdf) The fact that a single high-altitude nuclear explosion could destroy the electrical infrastructure across a majority of the U.S. vastly exceeds the damage which would be cause attacking a single city.

Other benefits(?) of a high-altitude nuclear explosion include a lack of nuclear winter, as no dust is propelled into the atmosphere, and the radioactive fallout being scattered by the jet stream, causing a slight increase over a wide geographical area while preventing a single “hot” area. No fires from the strikes, and no pressure waves.

The initial negative impact of such an event would be the destruction or damage of the technological infrastructure modern nations depend upon. Modern vehicles require computers to operate. Fry those computers and vehicles will not work. Cell phones would no longer work, cutting people off from their sole source of information. No internet, electricity, radio equipment, banking, or other niceties people rely upon. The destruction of airplanes as their electronics are fried, leaving them to resort to dead-stick landings, many of which would not be successful. People at work could become stranded far from their homes and families. The blinding of anyone looking at the explosion when it occurs.

Secondary negative impacts include a lack of water as water towers run dry without electricity to refill them, food spoilage due to a lack of refrigeration, heat/cold related injuries and deaths, deaths from a lack of life-saving medications, and the eventual failure of certain nuclear powerplants unable to utilize shutdown measures. While the initial uncertainty would prevent a massive negative public reaction, as time went on this would eventually happen. The looting of stores for supplies would add to the unrest. As most people fail to stock enough food to last more than a few days, starvation would quickly become an issue. Chemical spills and other leaking toxic material could cause localized areas of death.

“Nine of 10 Americans are dead from starvation, disease, and societal collapse. The United States of America ceases to exist,” warned the report declassified by recently decommissioned U.S. Commission to Assess the Threat to the United States from Electromagnetic Pulse (EMP) Attack.” (https://www.washingtonexaminer.com/washington-secrets/new-emp-warning-us-will-cease-to-exist-90-of-population-will-die) So there you go, you can have your nuclear war which results in the death of 90% of the world’s population without the additional negative effects of nuclear winter and a radioactive wasteland. You could have several nukes hit major cities as well, to increase the physical destruction and leave some uninhabitable zones. You would end up getting some immediate global cooling, but that would fade over the years.

As for your question, how big could a nuclear war be without causing an apocalypse, a study from 2018 stated that using more than 100 nukes against an adversary would cause harm to the aggressor nation. (https://www.mdpi.com/2313-576X/4/2/25) I am sure some of this depends upon the yield of the weapons, but it is a good starting point. This number does not take into account high-altitude EMP bursts. A report by Rutgers University (https://climate.envsci.rutgers.edu/pdf/WiresClimateChangeNW.pdf) states that a full-scale nuclear war between Russia and the U.S. would result in a nuclear winter which could last for years. This would involve the launch of ten thousand nukes, so a bit more than the hundred or so quoted above.

It might help to explain the purpose for asking the question. It seems unlikely that people would get into a nuclear exchange and stop when they reached the point of no return. If they have resorted to nukes, things are bad.