I don't now who the BS in econ student you're referring to is, as it's not the context of the article. We have had massive SO2 emissions from past stratovolcano eruptions.

Sure - there is definitely some gap between these natural processes and the artificial processes being proposed, but it is a narrow enough gap that it does preclude a fair number of second-order effects, compared to almost all geoengineering ideas that do not have such natural experiment equivalents.