Sure you can question it. You can question gravity as well.
The behavior of CO2 in the atmosphere is key to the issue of GW and if you don't understand the foundation of it, it is a very good part of the issue to ask questions of.
Einstein made a pretty good reputation for himself by questioning gravity.
The GW zealots (of which I assume you are a member) focus on small changes in CO2 causing the climate shift and that the "magic number" where we "didn't really see anything" and it's "gone beyond our ability to stop" is just a few 0.001%s away. Absorbtion of heat, wavelength, etc. is all part of the attempt to make it sound scientific. No credit is given for factors that might reflect heat or the increase in sun spot activity that just generates more heat to get absorbed.
BTW - CO2 "caused" the global cooling in the late 60s and early 70s.