The atmosphere approximately represents about 1.54x10^22 litres of air (not including changes due to density and temperature, on a purely volumetric assessment...)
so we have to process 92.8 ppm of the atmosphere per year in order to remove 1GT of CO2....
1.6 trillion cubic feet per second.....
It seems we need to bolster our conservation efforts if we are to save the oceans from a pH death in 40-50 years, when the available calcium carbonate to neutralize carbonic acid in the ocean, runs out....