In a comment to a recent question, it was pointed out that Biosphere II failed in part because too much CO2 was absorbed by the concrete, leaving insufficient oxygen in available CO2 to be released by plants in photosynthesis.
We know that one of the ways scientists and engineers are hypothesizing to reduce CO2 levels, in order to reduce the effects of global warming, is to investigate carbon capture systems, wherein CO2 is captured in, say, calcium carbonate and then buried.
This evoked in me an interesting story line and plot device.
It's about the Law of Unintended Consequences.
Is it feasible to capture so much CO2 on earth and make it permanently unavailable to photosynthesis, that the levels of oxygen in our atmosphere fall to levels that can no longer sustain life on earth?
This is NOT about HOW this capture is done, or even if it is doable. It's about, theoretically, given the current amount of CO2 that needs to be captured to reduce global warming, and the future ongoing rate of production and release of CO2 through the burning of fossil fuels, respiration, farting, and so on, if humans captured enough CO2 (and unintentionally made it unavailable to photosynthesis) to reverse global warming, would so much oxygen be captured that there is not enough left to sustain life?
In other words, is it feasible that we could unintentionally substitute one extinction event while trying to prevent another?
Some useful data that I have researched is:
Oxygen levels today 20.9%
Minimum oxygen levels for proper human functioning without adverse effects 19.5%
Oxygen levels have been dropping as CO2 levels are increasing, hypothesized to be in part from oxygen used in combustion
Any oxygen removed by 'sinking' CO2 is no longer available to replenish this depleted oxygen through photosynthesis - a double whammy - oxygen used up in combustion and not replaced by photosynthesis.
Closest figure I have for projected oxygen depletion WITHOUT CO2 sinking is a drop to 20.8 by the end of the century.
I have not found any research that gives a figure that says how LOW CO2 levels have to fall to REVERSE global warming (i.e., is it below the C3 plant compensation point?).
But I have not found any research that ties it all together in a future projection. The closest is this