I guess if you're looking for a reason to ignore the best available data, you'll be able to find it. That particular volcano is located in the middle of an ocean, where the winds freely bring fresh air from around the world.

Note that you cannot identify periods of local volcanic activity from periods of volcanic quiescence in the data at all, even though the data clearly shows a seasonal fluctuation caused by northern hemisphere vegetation that is thousands of miles away. Clearly the volcano itself has zero effect on the readings. Local effects are not present in the data, but global effects are.

You say it is difficult to find "numbers" in this argument, yet you scoff at the best data available for reasons that are clearly incorrect, based on the data itself. Perhaps you should take a closer look at whether you are really interested in what the data says. One of the hardest things to avoid in science is the tendency to look to the data for confrimation rather than enlightenment. Elements on both sides of this argument are guilty of that.

Take care.