Something that would shade to the right, controlled degree, the upper atmosphere
without provoking such as a 'nuclear winter'. Finding a way to control volcanic activity, for example.
And some way, also controllable, to adjust chemical balances in the ocean.
This would come, presumably, after having tackled the main problem and having achieved a radical socio-political and economic-financial transformation of all 'globalised' cultures, for as the article says, in the words of McPherson:
... “There’s not much money in the end of civilization, and even less to be made in human extinction.” The destruction of the planet, on the other hand, is a good bet, ... “because there is money in this, and as long as that’s the case, it is going to continue.”...