5 ms·

Could someone ELI5 why a few hundred above ground nuclear explosions today would "wrap the planet in a blanket of soot and block out the suns rays" when post wo

Could someone ELI5 why a few hundred above ground nuclear explosions today would "wrap the planet in a blanket of soot and block out the suns rays" when post world war America detonated hundreds of Nukes outside Vegas and nothing significant can be said about the environment there? Yes, the size of the blasts possibly, but the pacific and the siberia tests by the US and USSR were probably much bigger than anything a ballistic missile could carry today, so . . .what are we missing ?

jgrimm 5y ago
I would assume that detonating a nuclear bomb in a desert would cause fewer debris than detonating one in a built up and dense area
danielsju6 5y ago
Modern cities burning.
JaimeThompson 5y ago
In part because they would be over cities and built up areas resulting in a lot more particles and soot entering the atmosphere. Nearly every nuclear test, if not all of them, took place in areas with very little such material.
- bombcar 5y ago
  Did WWII blacken the planet with soot from firebombing? The bombing of Tokyo alone was 1.6 megatons of bombs, for example. I honestly have no idea, and perhaps our sensors were not accurate enough at the time.
  - regularfry 5y ago
    My guess, based on little other than a gut feel, is that while a lot of explosives were dropped on Tokyo, the energy was not concentrated enough to lift the soot high enough to be a global problem. But also, 1.6Mt just isn't that big a blast if you're talking nukes. Yes, it's bigger than current individual service warheads, but not by all that much. The B83 goes up to 1.2Mt. To put another bound on the question, Krakatoa was estimated at 200Mt in a single blast, and that definitely did affect the global climate. Again gut feel, but my suspicion would be that many distributed explosions around the globe totalling 200Mt would be worse in terms of direct effect just because there would be more physical mass available to be thrown into the air. Plus the soot would be radioactive.
- gshubert17 5y ago
  I live close to the site of the Marshall fire in Colorado which destroyed a thousand homes at the end of 2021. The amount of soot was surprisingly large. After post-fire snowfalls, snow pushed to the edges of parking lots was blacker than usual, probably from soot already on the ground that got scraped up with the snow. The other day I saw a couple of workers shovel soot off the Costco roof into a truck. In addition to more soot than I expected, it was more toxic (according to local reports) from all the plastics and chemicals that were burned.
toyg 5y ago
> the siberia tests by the US and USSR were probably much bigger than anything a ballistic missile could carry today I doubt this very, very much. Also to note: those were single blasts (as opposed to the dozens that would now cover any given region), some were underwater, none of them interacted with amounts of structures and living matter comparable to a populated city.
- Arubis 5y ago
  s/could/would/ My layman’s understanding is that huge warheads are a less efficient usage of nuclear materiel (in terms of sheer destruction) than a larger number of mid-sized warheads.
jcranmer 5y ago
The usual explanation boils down to the fuel load of cities. Another possible explanation is... the potential impact of nuclear weapons are greatly overestimated to make nuclear war too unbearable to countenance. There's a very big unknown here, which is how much soot a nuclear-induced conflagration of a city pumps into the stratosphere. We know that stratospheric soot would induce global cooling, for a time period of at least a few years, based on the observed effects of existing natural stratospheric soot pumps known as volcanoes. And we also know that without stratospheric pumping of soot, climatic effects are at best localized in both space and time (see, e.g., Kuwaiti oil well fires). Personally, I am very unconvinced by the assertion that nuclear weapons causes severe global cooling. The most powerful volcanic eruptions in recorded history are VEI 6 or VEI 7, which means they erupted up to around 100 cubic kilometers of stuff. If you assume a city has an average height of 100 meters (for the sake of round numbers), you'd need a firestorm to completely consume 1000 square kilometers of city to produce the same volume of material. Furthermore, a volcano's eruptive column is a relatively narrow plume of ejection as opposed to a broadly dispersed firestorm base, so it seems that you'd have a far lower conversion rate of material into stratospheric soot--and correspondingly you'd need to burn even more area to achieve the same effect. And at the end of the day, even the most severe volcanic winter in recorded history (1815) happening today would be roughly equivalent to rolling back global warming to 1850. For less than a decade.
awb 5y ago
I think the timeframe is a factor too. If you explode 10k nukes within 10min, that’s a lot more dust all at once than 100 nukes over a period of multiple years. I’d imagine it’s like filling a sink with water (and the drain slightly open) and use dye to simulate nuke debris. Try one or two drops every minute for ten minutes, vs. an entire cup of dye all at once. Obviously the actual climate models are far more complex but for ELI5, I think this is the general idea.
b_t_s 5y ago
Many reasons, the first few I can think of are: 1) It's not a _few_ hundred, it happens to be exactly 100 in Nevada. 2) That was spread over many years vs a couple days of a war. 3) They were in a barren desert, the "safest" place we could find. 4) They were all early bombs, nothing compared to the modern stuff. H-bombs literally use nukes as detonators, so it's like comparing blasting caps to C4. We quickly realized this was a terrible idea(some tests in NV had intense fallout in NY) and stopped doing atmospheric tests by 1963.
riskneutral 5y ago
I don't think nuclear winter is the biggest risk from a "small nuclear war." I'm not an expert at all, but my understanding is that the nuclear winter narrative was outdated and overhyped (especially when thinking about a detonation of two or three warheads, rather than hundreds or thousands).
LargoLasskhyfv 5y ago
They didn't do that in a single day, instead spread over a decade, or even more. Up until some test ban.

jgrimm 5y ago

I would assume that detonating a nuclear bomb in a desert would cause fewer debris than detonating one in a built up and dense area

danielsju6 5y ago

Modern cities burning.

JaimeThompson 5y ago

In part because they would be over cities and built up areas resulting in a lot more particles and soot entering the atmosphere. Nearly every nuclear test, if not all of them, took place in areas with very little such material.

bombcar 5y ago
Did WWII blacken the planet with soot from firebombing? The bombing of Tokyo alone was 1.6 megatons of bombs, for example. I honestly have no idea, and perhaps our sensors were not accurate enough at the time.
- regularfry 5y ago
  My guess, based on little other than a gut feel, is that while a lot of explosives were dropped on Tokyo, the energy was not concentrated enough to lift the soot high enough to be a global problem. But also, 1.6Mt just isn't that big a blast if you're talking nukes. Yes, it's bigger than current individual service warheads, but not by all that much. The B83 goes up to 1.2Mt. To put another bound on the question, Krakatoa was estimated at 200Mt in a single blast, and that definitely did affect the global climate. Again gut feel, but my suspicion would be that many distributed explosions around the globe totalling 200Mt would be worse in terms of direct effect just because there would be more physical mass available to be thrown into the air. Plus the soot would be radioactive.
gshubert17 5y ago
I live close to the site of the Marshall fire in Colorado which destroyed a thousand homes at the end of 2021. The amount of soot was surprisingly large. After post-fire snowfalls, snow pushed to the edges of parking lots was blacker than usual, probably from soot already on the ground that got scraped up with the snow. The other day I saw a couple of workers shovel soot off the Costco roof into a truck. In addition to more soot than I expected, it was more toxic (according to local reports) from all the plastics and chemicals that were burned.

toyg 5y ago

> the siberia tests by the US and USSR were probably much bigger than anything a ballistic missile could carry today I doubt this very, very much. Also to note: those were single blasts (as opposed to the dozens that would now cover any given region), some were underwater, none of them interacted with amounts of structures and living matter comparable to a populated city.

Arubis 5y ago
s/could/would/ My layman’s understanding is that huge warheads are a less efficient usage of nuclear materiel (in terms of sheer destruction) than a larger number of mid-sized warheads.

jcranmer 5y ago

The usual explanation boils down to the fuel load of cities. Another possible explanation is... the potential impact of nuclear weapons are greatly overestimated to make nuclear war too unbearable to countenance. There's a very big unknown here, which is how much soot a nuclear-induced conflagration of a city pumps into the stratosphere. We know that stratospheric soot would induce global cooling, for a time period of at least a few years, based on the observed effects of existing natural stratospheric soot pumps known as volcanoes. And we also know that without stratospheric pumping of soot, climatic effects are at best localized in both space and time (see, e.g., Kuwaiti oil well fires). Personally, I am very unconvinced by the assertion that nuclear weapons causes severe global cooling. The most powerful volcanic eruptions in recorded history are VEI 6 or VEI 7, which means they erupted up to around 100 cubic kilometers of stuff. If you assume a city has an average height of 100 meters (for the sake of round numbers), you'd need a firestorm to completely consume 1000 square kilometers of city to produce the same volume of material. Furthermore, a volcano's eruptive column is a relatively narrow plume of ejection as opposed to a broadly dispersed firestorm base, so it seems that you'd have a far lower conversion rate of material into stratospheric soot--and correspondingly you'd need to burn even more area to achieve the same effect. And at the end of the day, even the most severe volcanic winter in recorded history (1815) happening today would be roughly equivalent to rolling back global warming to 1850. For less than a decade.

awb 5y ago

I think the timeframe is a factor too. If you explode 10k nukes within 10min, that’s a lot more dust all at once than 100 nukes over a period of multiple years. I’d imagine it’s like filling a sink with water (and the drain slightly open) and use dye to simulate nuke debris. Try one or two drops every minute for ten minutes, vs. an entire cup of dye all at once. Obviously the actual climate models are far more complex but for ELI5, I think this is the general idea.

b_t_s 5y ago

Many reasons, the first few I can think of are: 1) It's not a _few_ hundred, it happens to be exactly 100 in Nevada. 2) That was spread over many years vs a couple days of a war. 3) They were in a barren desert, the "safest" place we could find. 4) They were all early bombs, nothing compared to the modern stuff. H-bombs literally use nukes as detonators, so it's like comparing blasting caps to C4. We quickly realized this was a terrible idea(some tests in NV had intense fallout in NY) and stopped doing atmospheric tests by 1963.

riskneutral 5y ago

I don't think nuclear winter is the biggest risk from a "small nuclear war." I'm not an expert at all, but my understanding is that the nuclear winter narrative was outdated and overhyped (especially when thinking about a detonation of two or three warheads, rather than hundreds or thousands).

LargoLasskhyfv 5y ago

They didn't do that in a single day, instead spread over a decade, or even more. Up until some test ban.