So WI the Tunguska Meteor actually impacted the surface? Would this produce a greater/lesser climate shift than previous volcanic eruptions a la 1816 the year without summer.
That depends. Allow me to explain as best I can. If it had impacted the ground, then there would have been a crater had it impacted on terra firma.
However, since it exploded above the ground, and was an air burst, it might have created a crater in the swamps around Tunguska, there's no evidence of that. That was proven in 1928, twenty years after the explosion. However,
one of the most outlandish theories is that it was a UFO from Mars that exploded above Tunguska.