The effective temperature under its usual assumption of unit emissivity The point is that an atmosphere that cannot absorb or emit radiation cannot interact with space whence the only temperature it is capable of measuring is the surface of the planet which therefore determines the thermal destiny of the atmosphere  Under those conditions the blanketing effect of the atmosphere is purely reactive in EE jargon namely on account of its thermal mass with no resistive component  It will therefore exert a damping effect on the diurnally varying surface temperature analogous to a capacitor but like a capacitor it cannot itself heat up the way a resistor does