From my limited knowledge of science, which is exponentially greater than that spouted by most climate nutters, you are entirely correct. The reason that they chose co2 to achieve their aims was after much debate, and non of it evidence based, but rather what could plausibly be sold to the gullible public. The aim ? Is to create enough indebtedness that will require transfers of natural resources of nation states to satisfy those debts. The business model will be carbon sinks that will produce never ending revenue via carbon offset credits purchased from those debt holders. Tin hat conspiracy theories, get in the real world, we are already here.