They've found evidence of periods of apparent high atmospheric SO2 in some ice cores. There are multiple reasons, outside of volcanoes, this could have occurred.
The fact that vulcanologists have no evidence of this eruption doesn't seem to trouble anyone on the "climate science" side. So much so, they _insist_ the volcanologists are just "missing" it. They also need it to exist, because it is their only explanation for widespread temperature anomalies around this time period. Whenever the model fails to predict something, they go searching for a volcano, seemingly. It helps because it has high levels of atmospheric distribution, other sources of SO2, obviously, do not.
And, on the back of this wholly incomplete work, they would like to purposefully put high levels of man made SO2 in the atmosphere to try to interfere with the climate. We should do our best to positively impact the climate. I have strong doubts about all of these radical SO2 ideas.
Ah, yes global cooling. The thing that has been predicted for at least thirty years by now. The most common argument is that solar activity is declining. Tough luck. CO2 is rising faster than the sun can become colder. We are in a solar minimum and yet we somehow break temperature records?
> CO2 is rising faster than the sun can become colder.
You are, at this point, just shadowboxing.
> We are in a solar minimum and yet we somehow break temperature records?
We broke records everywhere on earth simultaneously? We did nothing to change our measurement strategy or equipment in the past 150 years? What annoys me is everyone finds their favorite justification for austerity and then just runs with it. It's not serious and it's not particularly good science.
https://en.wikipedia.org/wiki/1808_mystery_eruption