Comment by BurningFrog

Restoring CO₂ levels will use plenty of money and energy, however it's done. It can still be very much worth doing!

I don't believe much in tree planting, since it uses up huge areas of the planet forever.

The best way is to separate out CO2 from the atmosphere and pump it into underground cavities. This is the just reversing natural gas extraction, which means it's well established tech. Aside from the separating CO2 part, but that's being worked on.

In a decade or three I expect solar powered machines like this slowly but surely turning the atmosphere back to normal.