This is based on the well known experimental result that a radio frequency arc deposits soot and "freshens" the air.
A number of large units would increase the oxygen supply of the global atmosphere and cut the excessive carbon dioxide level. The total power to carry this out is around 6000 Giga Watt for 5 years to restore the global atmosphere to the healthy level 1000 years ago over a longer period it will bring the oxygen level up to the level before the asteroid hit us 265 million years ago.
The power to do this can come from the fusion reactor described in another of my suggestions.
Smaller domestic units may also be made.
The device splits the carbon dioxide molecule to carbon and oxygen.
An array of copper rods excited by high voltage radio frequency current, this is placed at the bottom of a tower vented at the bottom with an extractor fan pulling the air though the array of rods.
The radio frequency excitation forms a radio frequency arc between the rods where the reaction takes place.
The exact values of the high voltage and frequency must be found by experiment but my guess is a potential of 100,000 volt, 50 megahertz.
The power can come from a proton fusion (Stellerator) running at the same frequency.