Geoengineering proposals are often unserious because the point is to give the appearance of doing something while the root cause goes unaddressed. "No need to reconsider those fossil fuel subsidies because [fanciful geoengineering proposal] will save the day!"
That has not at all been my experience of listening to such people.
And, what subsidies? The fossil fuel companies are just trying not to get legislated out of business, last I checked. In my book the disruptive subsidies are for corn (encouraging irresponsible land use; solar panels in those fields would be far more energy efficient).
I’m as uninterested in debating someone who denies the existence of fossil fuel subsidies as I am in debating climate denialists. I recommend that interested parties perform a trivial web search.