My big problem with gloom and doom prophecies concerning nuclear winter with 50 nukes is that in 1958 there were over 100 nuclear tests, most of which were above ground and we didn't get nuclear winter. Now its true that testing environments are very, very different from actual combat use and specifically designed with safety in mind, but we're talking about 100 above ground nuclear detonations so the effects are not negligible.
Most of nuclear test were in desert or on tiny tropical island or in Ocean or underground.
not over populate city full of plastic, Wood, paper, petrol or surrounded by Forrest.
i have read the papers by Michael Mills and Brian Toon. There is a realistic chance for nuclear winter, if 50 city are nuclear hit.
it would like a vulcans heavily erupt and fill the sky with ash. only in bigger scale