This of course depends on the time frame one wants to achieve, but assuming we want to remove carbon dioxide as quickly as we added it, that means we would need

This of course depends on the time frame one wants to achieve, but assuming we want to remove carbon dioxide as quickly as we added it, that means we would need some operation comparable in size to the global coal, oil and gas industry extracting carbon dioxide from the atmosphere around the clock. And while I agree with you, exponential growth is in some sense hard to predict, I don't really see us starting such a gigantic endeavor unless we are absolutely forced to by the consequences of climate change.