You write: "To reduce temperatures by 0.1C, about 222 billion tonnes of CO₂ would need to be removed from the atmosphere, costing trillions of dollars in even the most optimistic cost scenario."

I find this both overly optimistic and overly pessimistic. First, it is by no means clear that merely reducing CO2 concentration by as little as 222 Mt would have a temperature cooling effect on a human timescale, although we do have historic examples from the Columbian Encounter and the Mongol Invasion of Europe that suggest it might over a few centuries. We know much more about rapid warming than we do about rapid cooling.

Second, removing 222 Mt can be accomplished at negative cost with already commercial systems on decadal time scales (biochar and bio-oil asphalt and concrete substitutions, for instance). There is no basis for saying that trillions of dollars in cost is the most optimistic scenario. These carbon cascading industries are profitable already.

For any number of more optimistic scenarios I would urge you to read Kathleen Draper and my book, BURN: Igniting a New Carbon Drawdown Economy to Reverse Climate Change (2018).