It's not a difficult problem; There are technologies that extract CO
2 from air and turn it in to carbonates that can then be land-filled (or used as raw material for such things as plasterboard). For example:
https://qz.com/1100221/the-worlds-first-negative-emissions-plant-has-opened-in-iceland-turning-carbon-dioxide-into-stone/
Jan Wurzbacher, Climeworks’s director, says it hopes to bring costs down to about $100 per metric ton of carbon dioxide.
So that's your initial Carbon Tax level - whatever the current cost of doing this actually is. Tax all fossil fuels at that rate; Give rebates to uses such as plastics that don't lead to atmospheric CO
2.
If the technology gets cheaper (as it should when scaled up); Or if other, cheaper CO
2 mineralizing technologies are developed, you can reduce that tax level accordingly.
If it's still cheaper to burn coal, oil or gas after paying that amount of tax, then that's OK - the taxes just get spent on extracting and burying the CO
2. If other technologies (whatever those might turn out to be) are cheaper than fossil fuel plus Carbon Tax, then users of fossil fuels will make the switch.
The only problem is political - governments need to implement this tax worldwide, on all fossil fuel production/extraction; And then ensure that the tax collected is used only for the manufacture and disposal of carbonates from atmospheric CO
2.
Mind you, even if the morons in charge of our major economies were not denying the underlying science, arranging a global tax, and then auditing the expenditure of the revenue to ensure it is all used to extract CO
2 from the atmosphere, would be a massive ask.
It's not a difficult problem to solve. But humans are pretty good at fucking up even simple solutions.