What is impossible about direct temperature manipulation schemes? I'm referring to proposals like building reflectors to directly lower the earth's temperature. There's nothing in principle preventing this from directly cooling the planet.
Also, what do you know about the physics of CO2 absorption/re-emission? CO2 absorbs what exactly? To start it's the 15 micron band. It is infrared radiation on the longer, weaker side of IR. How much heat does 15 microns contribute to, and what types of molecules [eg ice or water, or only atmosphere?] can actually interact with 15 microns vs. being transparent to it? Since water vapor already absorbs at 15 microns, how does that modulate the effect of CO2? Does CO2 even re-emit 15 microns back to earth, or does it just cause co2 to wiggle a little bit (it definitely causes it to wiggle, but what frequency does it re-emit, if any?) Quantifying heat caused by 15 microns is not something you will find information on, even though the entire carbon based global warming arguments depend entirely on it. But there is another relevant point to be made:
15 micron is in the terahertz spectrum specifically. This spectrum is notoriously difficult, if not impossible, to build any sort of transmitter or receiver for, mainly because the air/water vapor simply absorb it in a short distance. To this effect I've heard one college physics professor who publishes his lectures on youtube argue that 15 microns is 99.9% already absorbed in the atmosphere by such effects [1] [eg adding more CO2 will make effectively no difference at all; it's all absorbed already]. We do know the main atmospheric window where energy can reflect back into space does not include the 15 microns band [e.g. CO2's absorption profile doesn't fall in the main atmospheric window]. My question for you is how much time have you spent thinking about absorption/EM spectrum based arguments that get at the actual mechanism of how carbon based global warming is supposed to work? Most people have not. I don't have all the answers, but the physics actually seems to imply it's possible if not likely we could be completely wrong in our assumptions about CO2 and global warming. I would challenge you to come up with a rebuttal to that, in the same way folks have not come up with a rebuttal to the argument you posted. So yes, we're having the wrong conversations.
As an alternate potential explanation consistent with the physics, CFCs do absorb in the atmospheric window, and even though they were banned decades ago it turns out they are on the rise again [2]