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Could anyone could survive a nuclear war and all that follows?

I have read many things saying they would, and read other science-based answers, but they all talked about a nuclear war that was relatively small (100 nukes fired between India and Pakistan). Would anyone survive a nuclear war of NATO vs. China and Russia, or something similar, where all the nuclear bombs they could fire were launched? I have read people would be better off in the Southern hemisphere, but how would they be, and how many people would survive?

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  • $\begingroup$ The title asserts nuclear winter but the question says war; if you assume just that there is "war" you may instead experience nuclear summer, in which the ozone is damaged, letting in solar radiation and overpowering the "winter"-causing particles released. I'm no expert on which would occur but answers could consider this. $\endgroup$ – Zxyrra Dec 16 '16 at 3:32
  • $\begingroup$ Just out of curiosity, have you bothered to read en.wikipedia.org/wiki/Nuclear_winter ? $\endgroup$ – Karl Dec 16 '16 at 7:08
  • $\begingroup$ I made a little edit... because "Israel and Palestine" exchanging 100 nuclear weapons is like a boxing match with three crates of hand grenades. I think you meant that other longstanding "I vs P" conflict. :D $\endgroup$ – MichaelK Dec 16 '16 at 8:05
  • $\begingroup$ @Karl Yes I have, and many times it referred to the India-Pakistan scenario rather than a scenario where the nukes of major powers were launched (like the above NATO v. Russia/China). $\endgroup$ – TechPro19 Dec 16 '16 at 21:09
  • $\begingroup$ @Zxyrra From what I've read, the nuclear summer would occur after the many particles from the firestorms caused fall to the earth. The ozone would be noticeably healed but would still be damaged by that time. I would like to know the chances that people would survive the nuclear winter, since those people (since already exposed to the solar radiation from the lack of ozone) would likely be the people who end up repopulating the earth and such. $\endgroup$ – TechPro19 Dec 16 '16 at 21:11
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To be honest, no one really knows. There are plenty of people who've modelled nuclear winters, and they've come up with answers ranging from 'very little happens' to 'pretty much all life on the planet is doomed'.

So to some extent, just pick whatever fits your narrative and go with it, there's as much chance of its being right as any other prediction.

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I've been looking at other answers, but I'd like to know, science based, if anyone could survive a nuclear war and all that follows.

Could anyone survive? Yes. Across the United States there are a variety of fallout shelters. Some are public, most are private. A few are for government use and hence, not publicized. Add to that, fallout shelters in other countries, like Canada. So, assuming people get to the existing shelters and they are not in the blast radius of a weapon, yes, some people could survive a nuclear war. How long they survive after the blast depends on the amount of supplies they have.

I've read many things saying they would, and read other science-based answers, but they all talked about a nuclear war that was relatively small (100 nukes fired between Israel and Palestine). Would anyone survive a nuclear war of NATO vs. China and Russia, or something similar, where all the nuclear bombs they could fire were launched?

There are estimated to be over 15,000 nuclear weapons held by the nine countries known to have such weapons. About 2,000 of those are on a "High Alert Status" meaning they are already programed with a target and could be deployed (launched) in minutes. Russia and the U.S. account for about 14,000 weapons and about 1,800 of the "High Alert Status" weapons.

So, let us say all 2,000 that are on "hair triggers" are fired. While we don't know the exact yield, a fair estimate for a modern weapon would 1 megaton each. Due to the wide range of devices and delivery systems, setting an average is not simple. Each five megatonnes of explosive power translates to about one ton of mass for the weapon. A 1 megaton device would clock in under a quarter ton. That is a good size, but manageable for several delivery systems, both short and long range. While we have tested much larger yielding devices (15MT, 25MT, 50MT), smaller is more practical. Also, as a device's yield grows, its destructive ability only matches that growth to a point. The reason is the earth's atmosphere.

It is the pressure of the atmosphere that spreads out a blast. As you go higher, the pressure of the atmosphere is less. This affects the nuclear blast in that it, like any wave force, will follow the path of least resistance. So, as the power of the blast increases, the area of planet's surface affect will not increase in proportion because the lower density of the upper atmosphere, having less resistance than atmosphere near the ground, directs the blast upward more than outward.

Indeed, the difference between 50 and 100 megatonnes at ground level would be very small because, even with twice the power, the 100 megaton blast would lose most of its power from the escape of energy to space as it would blast all the way out of our atmosphere. At least that's the theory based on the biggest test ever.

Assuming 1 megaton each, that means a total force for all 2,000 would be 2,000 megatonnes (2 BILLION tonnes of TNT). That's enough force to throw millions of tonnes of debris high into the atmosphere. Add to that all the ash and smoke from the fires caused by weapon detonations, easily adding millions more tonnes of radioactive material in the air. These particulates blocking sunlight, and the fact that they are a radioactive, is what gives us the term "nuclear winter". That debris would remain in the atmosphere until it settled back to the ground. Rain would be the biggest player in that process. Wind and rain would carry this radioactive fallout across much of the planet's surface.

No one knows, for sure, how long it would take that much matter to rain back to earth, but a few years is easily possible. During that time, sunlight reaching the surface would be reduced. This would affect the earth's ecosystems, as plants die or are reduced in number, the higher organisms would suffer as well. On top of that, it would be colder with less sunlight.

Of course the air clearing is both curse and blessing. While clearing air means more sunlight and heat it also means that some areas get hit by the radioactive rain. Such places will be contaminated by fallout for many years, anyone in these areas will most likely die, some faster than others.

I've read things would be better off in the Southern hemisphere, but how would they be, and how many people would survive?

This is due to the fact that most targets for nuclear attacks are in the northern hemisphere, hence, that's where the firestorms and ash clouds will originate. Weather patterns between the north and south are such that most of the airborne ash will remain north of the equator. That's, in part, due to the sun's effect on air near the equator, it's hotter there so more air is pulled in from the colder areas near the ground and, likewise, expelled toward the colder areas at higher elevations. While this air current wouldn't stop ash traveling to the southern hemisphere, it would reduce it.

That translates into less radiation delivered via fallout and more sunlight reaching plants in the southern hemisphere. Both of these factors will mean the survival rate in the southern hemisphere will be greater than that of the northern hemisphere. In all likelihood, the much greater.

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    $\begingroup$ Don't forget that we have historical observations of large volcanoes that did put millions of tonnes of debris and sulphate aerosols into the upper atmosphere. We survived. But there were global climate repercussions, so these observations certainly do not rule out a nuclear winter. $\endgroup$ – nigel222 Dec 16 '16 at 11:50
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    $\begingroup$ Also there was the Toba supervolcano eruption about 78,000 years ago. At about the same time the human race went through a genetic bottleneck: the total number of living human beings dropped to a few thousand. Cause and effect? Not certain, but likely. A supervolcano puts gigatonnes of debris into the upper atmosphere. Life survives these, but a species may not. $\endgroup$ – nigel222 Dec 16 '16 at 11:56
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    $\begingroup$ Surviving the immediate effects and long term survival are two very different things. A fallout shelter plus being away from the bombs is enough to give you survival in the short term. Long term is quite another matter--you emerge into a wasteland where nothing grows until the soot finally comes down out of the sky. $\endgroup$ – Loren Pechtel Dec 18 '16 at 1:01
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Yes the southern hemisphere will fair much better than the northern, there are no nuclear states in the southern hemisphere so there are fewer targets. the continents are widely spaced reducing secondary fallout. Fallout and ash will only slowly cross the equator due to the air flow patterns, and will not make it to antarctica at all for the same reasons.

Generally rural areas with low populations far from cities will fare the best. isolated water systems (like the salt lake system) will help reduce contamination, the smaller the better.

Aside from the political and economic effects, (which admittedly would be huge) the southern hemisphere is not going to be hit as hard.

here are two detailed projections of the effects.

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    $\begingroup$ On my evil overlord checklist, I have included "remember to also target the Southern Hemisphere." You're all doomed! $\endgroup$ – SRM Dec 16 '16 at 3:27
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    $\begingroup$ bah if that's your goal target some of the super volcanoes like yellowstone and taupo. they are in both hemispheres and will do the bulk of the work for you. $\endgroup$ – John Dec 16 '16 at 13:35
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The general consensus by most governments is 3 weeks for fallout to clear. it doesn't matter how many or how big the bombs are, the decay rate is still the same. HOW MUCH that is released is determined by size of warhead and how far off the ground it was detonated. However, that being said, in a full scale nuclear war, how much of the planet would be covered in clouds is up for debate. However DoD has estimated that at least 106 million would die from the blasts and radiation (for those that aren't in a shelter or don't have one) so that is nearly 50% of the US. There would be food and water shortages so there will be starvation of course. Then there are those who would be killed in looting in areas that weren't hit and by marauders (yes, those would really become a thing). Then there would also be disease. I estimate that the nuclear blasts and rads alone would kill at least 48% of the world population and the mayhem after that to be to probably kill another 10-20%. This would include starving people and those got by the wolves while they're still undecided and not fully realizing the situation. So, approx 32% of the world population would still be alive by the time some sort of order is restored, but that is my guesstimation, and not based on anything official, so take it how you will.

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