If only we could use massive floating solar arrays anchored over the Mariana Trench, and use that power to create carbon fibre from atmospheric CO2. Some could be used in industry, but let’s scale that up until we are creating solid spheres of carbon 1-2m in diameter and dropping those into that subduction trench. It will take some time, but most ought to be pulled down into the crust via subduction, and return carbon to the mantle where it ought to be locked away for several hundred million years.
Keep doing that until we have gotten things back down to under 200ppm.