Reckoning something doesn’t really cut it for a question like this. Modelling is required, and the article Exano Mapcase linked to explains why there is a lot of uncertainty. A firestorm in a city is not necessarily comparable to a forest fire. The more intense the fire, the greater it’s ability to introduce smoke particles into the stratosphere.
Let’s see. Here’s a shot from space of the 2007 “Wicked Fire” forest firein Gallatin National Forest. That was a 26,500 acre fire, which as forest fires go, isn’t that big.
The buildable area of New York City (minus streets and water) is 154,000 acres, or about six times the size of the Wicked Fire.
For point of reference, smoke from the firebombing of Dresden was detected at 15,000 feet, while the Mount St. Helens eruption threw a column up to 80,000 feet, so we can probably use those as our minimum and maximum.
Also compare the Southeast Asian Hazein 1997 which covered three million square kilometers, somewhat smaller than the size of India.
Leaving aside the issue of how smoky a flaming Big Apple would be compared to a typical forest (you can try to extrapolate from Sailboat’s photo if you want) it’s pretty clear that WarmNPrickly’s 'hundred burning cities" – or let’s say 20 burning cities – is going to generate a metric buttload of smoke.
That’s pretty much the explanation given in the Wikipedia article on nuclear winter:
Obviously, they are assuming that the entire city would be more or less burning at once, plus the smoke is probably sootier and darker than from forest fires (some of which can be intense enough for stratospheric injection; not so much related to the total size but the area and material currently burning, and pyrocumulonimbus clouds).
Indeed they have had. But let’s not lose sight of the fact that the major volcanic eruptions through history have released enormously more energy than would be released by the detonation of all our nuclear devices, and have also released many megatons of both gas and particles clear into the stratosphere.
Also, as I look into this, I find the concept remains more active than I had thought it was. This wikipedia article considers the current state of the idea and the research on it.
The major information that I was aware of that criticizes the concept is discussed in the “Criticisms” section, particularly in the “Firestorm formation” section.
Most notably, some of the assumptions of the nuclear winter scenarios do not appear supportable based on history. Specifically, we have had firestorms in cities - including firestorms due to the detonation of nuclear weapons - but none of those firestorms managed to inject soot into the stratosphere, which would be required if the nuclear winter scenario was to come about. Further, all the soot from these firestorms quickly rained out of the lower atmosphere.
Still further, Carl Sagan was predicting a nuclear winter type event when the retreating Iraqis lit off all the Kuwaiti oil wells as they retreated in Gulf War I - I remember watching him on TV talking about it. Nothing happened.
And finally, we have had any number of large nuclear explosions near forests and jungles, which failed to ignite firestorms in the forests and jungles, and while we have had enormous forest fires in the United States and around the world, none have injected significant quantities of soot into the stratosphere.
This is not to say that a major nuclear war wouldn’t be a cataclysm - it certainly would be, particularly since the destruction would specifically target Man and Man’s works. But nuclear winter seems to rest on a lot of assumptions that are not well supported.
I had not realized the idea was still receiving any serious consideration, but the Wikipedia article suggests it is.
Iran has stated publicly that it would use them to destroy Israel. I think that, given their behavior, it is quite appropriate for us to consider the possibility that they mean it.
This is not to say that I’m somehow claiming that Pakistan isn’t a threat - it certainly is and its stability (and rationality) is very questionable. And, I do agree that India-Pakistan seems like the most likely flashpoint - for now anyway.
Lower atmosphere. Will rain out.
A minor “burp” as far as volcanoes go. Think Krakatoa, since that is the last one that eliminated a complete summer around the world and led to beautiful sunsets for years afterward.
To get a comparison of scale, recognize that he blast from Krakatoa was heard more than 2,000 miles away, and the shock waves were recorded 7 times as they circled the earth.
Mount Pinatubo’s eruption might be a better high end marker, given its much larger size than St. Helens’s cloud and our much better ability to quantify its atmospheric contamination than in 1883. The article attributes much of the global climate change from Pinatubo to the very large amount of sulfur dioxide released. I don’t know if a nuclear firestorm would release those amounts of SO2.
OTOH, a very large airbursted thermonuclear weapon (not that very many of those exist anymore) is capable of releasing a tremendous amount of heat over a very wide area. Your garden variety one MT weapon (and most extant devices are smaller), airbursted at optimum altitude (ballpark 7km height, if I’m doing the calculations detailed in the nuclear weapon archive correctly), will emit radiation of at least 8 calories/cm^2 out to at least just over 9 km away. That radiation intensity will cause 3rd degree burns to exposed skin, and ignite paper, IIRC, over a >260 square kilometer area. For one bomb.
(I find the calculations detailed in the archive to be a little ambiguous: the scaling equations they mention don’t detail whether they are slant ranges or ranges from ground zero, assuming optimum burst height. In any event, I used the lower bound, the higher one is 11.5 km away.)
As a pretty data point of who-knows-how-reliability, here’s a wiki chart purporting to show the relationship between device yield and height of mushroom cloud. I imagine it changes greatly depending on what the device ignited beneath it.
Only if there was a source for it.
The nuclear burst itself would have a negligible impact on these nuclear winter scenarios. Such a scenario depends critically on the burning of all burnable objects, and the injection of the resulting soot and ash into the stratosphere so that it will remain there long enough to substantially upset the energy balance of the earth due to a lack of insolation.
The problem here is that burning cities and forests don’t have enough energy density to elevate particulates high enough into the atmosphere to get them above storms. Hence the material rains out quickly. Indeed, the presence of the material works in many circumstances to actually precipitate storm formation.
Essentially, the air columns above these fires rise and cool and spread. The fire is not and can’t be hot enough to begin with to retain the amount of heat necessary in the column so that the column can rise clear to the stratosphere. It cools off first.
The blast itself DOES have sufficient energy density, but the blast is over pretty much instantly and the amount of material lofted that high is very small.
Volcanic eruptions, if large enough, might have the energy density (I’m not sure of that…) but will have sufficient force to loft large quantities of material high enough just by kinetic effects, as if the material was shot out of a cannon. The smaller components of this lofting will remain airborne for possibly years.
This is pure nitpicking, but isn’t a great deal of the energy in a volcano seismic energy – shaking, the physical motion of vast masses of rock, lava, and ash, and so on – whereas the energy in a nuclear explosion is much more directly destructive – flash, heat, and shock-wave? The bomb’s energy is more focused on very short-term harm.
Sure.
But what we’re considering here is whether these devices have the capacity to harm the ecosphere to a level that is greater than we’ve seen in recorded history from the largest volcanic blasts of which we have knowledge. This would seem to require comparisons of energy releases, to some extent anyway.
The source I mentioned says that it is due to black soot, which is apparently pretty effective at blocking sunlight and fine enough to stay in the air for a while. More importantly, it also absorbs sunlight (SO2 is mostly reflective), heating the atmosphere and causing air to rise further.
You mean that they transport their nukes in a way similar to how the US does it?
Nothing particulate will stay in the air if it rains. To get something like that to remain airborne for more than a short time, you have to get it above the weather. That’s the point here.
It obvious that we need to do some field testing. Let’s call MythBusters.
Hmmm, these scientists seem to disagree with your assertion, Bemused, that the smoke won’t get into the stratosphere: “The smoke-laden air rises to the upper stratosphere, where removal mechanisms are slow, so that much of the stratosphere is ultimately heated by the localized smoke injections. Higher stratospheric temperatures accelerate catalytic reaction cycles, particularly those of odd-nitrogen, which destroy ozone.”