Hardly seems necessary to "prove" something on Venus when ya have ta be oblivious to the obvious by lookin at obvious things like what makes up the vast majority of green house gases right here on this God created planet extrodinaire!!! I'm just sayin...
I agree that it shouldn't be necessary to use Venus as proof, but we can, so we should. This method is air-frickin'-tight. They can't argue it without sounding stupid. 1+1=2, and that's that. Well, unless you are doing Common Core math, then 1+1=whatever you feel it should equal.