There is about six million (6,000,000,000) times more carbon in sedimentary rocks like limestone, shale and sandstone than in the atmosphere. Compared to the lithosphere, atmospheric carbon is a rounding error.
Carbonic acid reduces the Ph of the ocean, so the theory goes. The question naturally arises, “What metal ore (oxide) could economically neutralize the Ph of the sea, creating a carbonate sediment in the process?”One possible effect which could take CO2 to the abyss would seem to be deep sea predators dying after having eaten food nourished by CO2 near the surface. IMHO.