In summary, small quantities of radiation from excited Greenhouse gases, at frequencies corresponding to a transparent window of the atmosphere, provide direct feed back of heat towards the earth, causing some heating, and towards outer space producing cooling. The proportion of this free radiation, relative to the amount of excitation energy trapped in the Greenhouse gas, is a characteristic of the gas and will be independent of both the total heat energy present and the concentration of a given Greenhouse gas.
[The calculations show] that there is little significant difference between the spatial distributions of heat captured by the Greenhouse gases along a vertical column within the troposphere, for a range of concentrations equal to that defined at present, nominally 380 ppm of CO2 and possible future concentrations of 760 ppm and 1140 ppm. While it is not possible to calculate the actual proportion of energy returning to the earth via these very low frequency photons passing through a transparent atmosphere, the proportion relative to that held by excited CO2 molecules will always be exactly the same, irrespective of the total amount or density of carbon dioxide present.
The findings clearly show that any gas with an absorption line or band lying within the spectral range of the radiation field from the warmed earth, will be capable of contributing towards raising the temperature of the earth. However, it is equally clear that after reaching a fixed threshold of so-called Greenhouse gas density, which is much lower than that currently found in the atmosphere, there will be no further increase in temperature from this source, no matter how large the increase in the atmospheric density of such gases.
As also shown by Miskolczi and others using different methods, Dr. Nicol finds that the "greenhouse effect" of CO2 is already saturated at present atmospheric levels and that future emissions will not affect temperature. Dr. Nichol shows that the IPCC concept of greenhouse gas back radiation to warm the earth is fictitious and that the true physical process is retardation of the exit of energy from the surface. He shows that the greenhouse gas absorption bands retard the exit of energy from the earth's surface, but that there is an upper limit beyond which further increases in greenhouse gas concentrations have no further effect. The surface is radiating at a fixed rate governed by the surface temperature and any increase in greenhouse gases with the same absorption bands will "widen the path" for heat to escape to the same degree as heat is retarded from escape, and therefore there is no additional warming. These principles hold for all greenhouse gases and are beyond saturation for the most important greenhouse gases, water vapor and CO2.