There would be little or no energy cycling between the mass bulk of the atmosphere and the surface so the surface need only be warm enough to provide the necessary radiation out at the top of the atmosphere. (newclimatemodel.com)
Blasting off from an airfield near the city of Nizhniy Novgorod (formerly Gorki) and flown by one of the manufacturer's test pilots, the MiG - 31 is capable of streaking through the sky at more than twice the speed of sound and reaching an altitude of 13 miles — putting you above the bulk of the atmosphere, high enough to see the curvature of Earth below. (discovermagazine.com)
The need for these fudge terms is probably nothing to do with feedbacks as usually defined, but with the need to correct for such simplifications as the one that supposes the greenhouse gases to cause the bulk of the atmosphere to be «black» (authors usage) or grey at all infra - red wavelengths. (realclimate.org)