[palmer]

Good luck growing enough food with plant-starving levels of CO2.

There's close to zero chance of that. Covering the planet in artificial photosynthesis (e.g. solar production of methane) would result in methane that would have to be stored or burned. Voila, CO2 back in the atmosphere. Same with algae producing fuels. Artificial photosynthesis producing solid carbon would only be as efficient as trees, maybe a bit more. Carbon capture of concentrated CO2 (e.g. from power plants) is just neutral, does not reduce ambient CO2.

The only way I can think of to get back to CO2 starvation is to develop an unlimited energy source like fusion and use it to capture ambient CO2. We have neither of those things right now.

[TigersEye]

That is quite a literal response to a facetious statement.

[ROCKLOBSTER]

The only way I can think of to get back to CO2 starvation is to develop an unlimited energy source like fusion and use it to capture ambient CO2. We have neither of those things right now.

Well, one thing we do have, is "CO2 starvation"....as there is practically 0% of CO2 in the atmosphere.