In this paper we quantify and attribute by inspection the constituent elements of the power intensity radiant flux transmission for the atmosphere of the Earth, as recorded in the following two published sources; Oklahoma Climatological Survey and Kiehl and Trenberth. The purpose of our analysis is to establish the common elements of the approach used in the formulation of these works, and to conduct an assessment of the two approaches by establishing a common format for their comparison. By applying the standard analysis of a geometric infinite series feedback loop to an equipartition (half up and half down) diabatic distribution used for the atmospheric radiant flux to all elements of the climate model; our analysis establishes the relative roles of radiant and mass-motion carried energy fluxes that are implicitly used by the authors in their respective analyses. Having established the key controls on energy flux within each model, we then conduct for the canonical model a series of "what-if" scenarios to establish the limits of temperature rise that can be achieved for specific variations in the controls used to calculate the global average temperature. Our analysis establishes that, for the current insolation and Bond albedo, the maximum temperature that can be achieved for a thermally radiant opaque atmosphere is a rise to 29°C. This global average temperature is achieved by a total blocking of the surface-to-space atmospheric window. In order to raise the global average atmospheric temperature to the expected value of 36°C for a putative Cretaceous hothouse world, it is therefore necessary to reduce the planetary Bond albedo. The lack of continental icecaps, and the presence of flooded continental shelves with epeiric seas in a global eustatic high stand sea level, is invoked as an explanation to support the modelling concept of a reduced global Bond albedo during the Cretaceous period. The geological evidence for this supposition is mentioned with reference to published sources.