Robert Speirs:
Volcanic activity is hard to predict, but my point was that some of the effects of “normal” volcanic activity do fit into a general pattern, with cooler summers and wetter winters.
The significant factor is the quantity and quality of ash, and where it ends up, and we might be able to model that data in a useful way. An event like Yellowstone or Cumbre Veja would be “normal” only in terms of geological history. In human terms it would be catastrophic, killing millions of us, radically altering the course of human historty, and remaking the world climatically and geographically.