Give it up man.. Those statements are only about the INCREASED efficiency of infra red on DIRECT radiation to objects OTHER then air.. Never blatantly says the "air can NOT be warned" by IR.. Only that the heat capacity of the AIR is much less than the heat capacity of a steakburger or a human body..
The air can be heated by energy...just not in the form of infrared....as if it really mattered since radiation is barely a bit player in the movement of energy through the troposphere. Conduction is the primary mode of energy movement through the troposphere...climate models, war mists, and luke warmers assume wrongly that radiation is the primary means of energy transport through the troposphere which is why the climate models fail so miserably.
If you have some experimental evidence that establishes a coherent link between the absorption of IR by a trace gas and warming in the atmosphere, I would like to see it. My bet, however, is that no such evidence will be forthcoming.