1808/1809 Mystery Eruption

I have encountered some who think climate change is no big deal because, so they say, we can just blow a few nukes and induce a controlled nuclear winter.

Scientific American has had articles on this. For $20 billion we can put enough sulfur in the upper atmosphere to block enough sun rays to stop global warming. But this solution has many, many problems. For instance, the sulfur eventually comes down and adds to the acidification of the oceans, already bad. The strategy is like drinking alcohol to calm down after you’ve done too much cocaine.

Throw one trillion* one-meter styrofoam squares coated top and bottom with aluminum (both sides in case they flip over) into random spots in the ocean. They degrade over the next few years, so they clear themselves out.

* Plus or minus a few orders of magnitude... haven't actually calculated this.

This doesn’t explain the contemporary South American observations, or the dendrological or viticultural data showing global cooling during that period.

Wikipedia cites cores from both Greenland and Antarctica. That would be some earthquake.

No, the eruption happened for sure. We just don't know which volcano it was. In particular the southwest pacific has lots and lots of volcanism from comparatively low peaks in island regions that don't leave a lot of obvious geology around where we can see it.