I think if we could muster a couple hundred dollar per ton carbon tax and use the revenue for removal, that would do it. Means putting about 4% of global GDP towards it, forever, but it could certainly be done. Back of the envelope call it removing 20 billion tons of carbon per year. 4 trillion dollars a year.

That's leaving aside the fact that we won't, of course, but it's not physically or economically impossible.