G. C. Simpson, C.B., F.R.S., on Some Studies in Terrestrial Radiation Vol. 2, No. 16. Published March 1928

It is assumed that water vapour is the only constituent of the atmosphere which absorbs and emits long wave radiation. From the results of upper air observations approximate values of the temperature and water content of the atmosphere at all heights and in all latitudes are adopted. Knowing the amount of water vapour and the temperature, it is possible to calculate the outgoing radiation if the absorption coefficient of water vapour is known. From consideration of the temperature of the upper stratosphere it is found that one millimetre of precipitable water in vapour form absorbs 30 per cent of the incident long wave radiation. With this value for the absorption coefficient the total outgoing radiation is calculated for each latitude from the equator to the pole, and it is found that over three-quarters of the earth's surface—from the equator to latitude 50°—the outgoing radiation is uniform and independent of the temperature of the surface. This result is due to the fact that it is only the layers of the atmosphere whose temperature lies between 220d and 286d which contribute to the outgoing radiation. As these layers are well within the troposphere between the equator and latitude 50°, the outgoing radiation is uniform from 50°S to 50°N. At higher latitudes the radiation falls off slightly, and at the pole itself it is 20 per cent below its value-at the equator.As the outgoing radiation is practically independent of the temperature of the surface, the problem arises as to how the temperature of the atmosphere readjusts itself to changes in solar radiation. This problem is considered in detail, but no solution is found.