What makes a nuclear winter so extreme and destructive?

Question

This may be a sort of, pertinent to the times, and disturbing question, inspired by the difficulties surrounding North Korea and the situation with it and nuclear weapons.

I've heard of this idea of "nuclear winter" that can result from a nuclear exchange, and more interestingly, very surprisingly, and disturbingly, that a major winter could be caused by even a "small" nuclear exchange, like on this paper:

http://climate.envsci.rutgers.edu/pdf/WiresClimateChangeNW.pdf

suggests that only "150 teragrams" of "smoke" released from a Nuclear exchange, would be able to produce a HUGE temperature drop of 7 degrees C for a couple of years or so, with attendant devastating effects on agriculture - indeed there's another version of this I saw with a map showing far greater temperature drops, like 20 degrees C or more, in places like Europe and North America (the USA) over land, right where the breadbaskets would be. Considering that it's not just crops but other plants as well that would be affected, its would seem to be a geologically significant event for a fair number of life forms, not just humans.

But the thing I'm having trouble with is just how is this possible, in particular, this magnitude, because it seems to be comparable to, if not greater than, natural events that would seemingly be of far greater magnitude. The 150 teragrams of carbon soot is only like a cube 400 meters on a side when solid, which is then vaporized and spread throughout the atmosphere, but that seems utterly tiny compared to the release of thousands of cubic kilometers of ash and other materials from volcanic and super-volcanic eruptions(*), much more asteroid strikes like Chicxulub releasing doubtless millions of cubic kilometers of material of all sorts. Is the soot really tens or hundreds of thousands of times more powerful per unit mass at cooling than anything released from any of these events would be? Or what? Further, especially considering that an event like Chicxulub would no doubt have ignited at least continent-scale areas of of forests in the area around it if nowhere else from the ejecta storm, which doubtless would have produced far more black carbon soot than burning down all the cities in a nuclear war, no? Yet this suggests effects that, while not equal, seem almost comparable - and this is considered for a much diminished set of arsenals, compared to what they were at their peak, suggesting the peak could perhaps even eclipse the Chicxulub at a tiny fraction of the total energy release from the latter. What would have happened to the Earth in an imaginary scenario where the 100 million megatons (400 zettajoules) of Chicxulub asteroid energy were replaced with 100 million megatons of hydrogen bomb mushroom clouds exploding over a comparable area of forests (alien attack? :) ) to those that the asteroid would have burned, 65-66 million years ago?

(*) See, e.g.

https://en.wikipedia.org/wiki/Toba_catastrophe_theory

https://en.wikipedia.org/wiki/Toba_catastrophe_theory#Volcanic_winter_and_cooling

where it is mentioned how that the Toba super volcanic eruption was first thought to have produced a big cooling, but more recent evidence suggests it may not have. Yet the nuclear war seems able to almost match it, with only 150 teragrams of carbon vs. 6 000 teragrams of SO2. Now of course maybe the former is better absorber (gas vs. fine dark solid), but literally so much better that the latter could barely move the meter (according to observational evidence, not the simulation mentioned), while the former would drop it 7 degrees C, 20+ in some areas? And that's just the SO2 component, what about all the other material released by the eruption to no doubt similar very great heights? And furthermore, how does this all fit in with Chicxulub? Is there any data on the "anti greenhouse" power of C soot versus SO2 and other materials released by volcanoes and asteroid strikes?

In short, what makes nuclear weapons so damn good at being destructive, compared to everything that nature seems to have in its arsenal short of the death of the Sun itself, despite seemingly the much greater raw power in terms of energy of the latter?

Answer 1

"In short, what makes nuclear weapons so damn good at being destructive, compared to everything that nature seems to have in its arsenal short of the death of the Sun itself, despite seemingly the much greater raw power in terms of energy of the latter?

1. It was answered in the source itself:

"The climatic effects of the use of nuclear weapons depend on the amount of smoke they would generate, and this depends on the targets. Nuclear targeting plans call for not only cities to be targeted, but also industrial facilities such as oil refineries and wells.

2. Turning to what nature has in its arsenal, there have been several mass extinctions on the Earth caused not by nuclear weapons but volcanism in its extreme form. Here's an article that identifies far more deadly factors coming along with volcanic phenomena bigger than supervolcanos called Large Igneous Province; not only energy alone matters in determining what is deadlier.

So what makes nuclear winter so extreme and destructive? Targeting nuclear weapons at mega-cities and industrial facilities where lots of toxic material are piled up.