Comment by pfdietz

Getting CO2 back to preindustrial levels by natural processes may take 100,000 years, IIRC. There will be some drawdown, but the ocean surface waters will become more saturated with carbon and that will stall. Over a longer time scale, CO2 will be pumped down into the deeper ocean. The true drawdown will require mineralization and precipitation as calcium carbonate, a slow process. The fossil fuel CO2 emitted each year corresponds to the calcium added to the ocean by erosion over about 100 years.