We should now be studying 1816, “the year without a summer” very closely.
Tambora, the cause of “the year without a summer” left a caldera 5 miles in diameter. The Campi Flegrei caldera is 7.5 miles in diameter. Try cubing those diameters to determine how much more “nuclear winter” CF could have caused. I would do it myself, but never was a math wizz.
Sunken Civ: I looked at some of the articles on CF that you provided the link for. On one of them I found the link below which is an interesting one on the language possibilities of Neanderthals.
http://www.abc.net.au/science/news/stories/s1323798.htm