They want to set a price on carbon. Not because they want to reduce carbon in the atmosphere, but because their future is built with carbon (graphene, carbon fibre, nanotubes, super conductors, etc etc)
They created a world that produces an abundance of carbon, and figured out a scheme to tax the hell out of it, and now conversely, the want to collect it so that they can sell it, to again tax it.
I assure you, if allowed to, they would come up with a scheme to charge us to simply breathe (which is a form of carbon production and capture) and then tax that too; make breathing expensive, and put people into breath debt or some shit.