[dplavery92]

It's worth mentioning that there has been some criticism[0] of the initial science behind the Nuclear Winter proposition. That said, smoke and soot can have a cooling effect on the Earth's temperature and CO2 (and other "greenhouse gasses") a warming effect because they absorb different wavelengths of light.

The sun is a very hot (~5500K) blackbody that emits radiation in a broad spectrum, but that spectrum peaks in the visible. Some of that light is incident on Earth and warms it up. Earth also emits its own blackbody radiation, but it's much cooler (~300K), so it emits much less power over all and its spectrum peaks somewhere in the long infrared. The system is in equilibrium when the sun has heated the Earth enough that the total energy radiated away from Earth is equal to the fraction of the sun's radiation that is absorbed by Earth.

Earth's atmosphere can change this equilibrium temperature by changing the fraction of incident energy that is absorbed by Earth, or changing its emissivity. Moreover, these changes can be wavelength dependent. Greenhouse gasses are gasses that are transparent in the visible spectrum but are reflective in the infrared, which allow in most of the sun's energy, but "trap" infrared energy that is being emitted by earth. Smoke and soot, by contrast, are very reflective in visible light (we can see them!) and so "block" much of the sun's energy from heating the Earth.

[0]https://en.wikipedia.org/wiki/Nuclear_winter#Criticism_and_d...