The Diurnal Smoothing Effect

Dai Davies, 190108

A fact that has often not been recognised by it's critics is that if the GHE is not significant there has to be an alternative. The Earth's surface is certainly warmer than it would be without an atmosphere.

Figure 1:

An alternative can be found in the Diurnal Smoothing Effect (DSE). The atmosphere cooling the surface during the day and warming it at night, results an an overall warming of the surface. This may seem counter-intuitive, but at its core the DSE is a simple physical process as illustrated in Figure 7 where the effect is calculated for a 1 ˚K (or ˚C) smoothing of the surface temperature between day and night.

The differential rate of surface radiation comes from the nonlinear relationship between energy radiated from the surface and its temperature, given by the Stefan-Boltzmann law as E = σT

The Open Climate Modeller repeats this calculation over a daily cycle to obtain mean daily values (for a typical temperate latitude not global means). It can be used to explore the DSE in depth.

Figure 8: A comparison of Earth atmospheres and the moon

Open Climate Modeller claculating DSE over a daily cycle

The condensing atmosphere approximately represents our atmosphere. As can be seen in Figure 4, surface level radiative transfer dominates surface-air thermal coupling and increases diurnal smoothing, and hence the DSE. At surface level, water vapour usually dominates radiative transfer, and carbon dioxide plays no significant role.

The radiative atmosphere has a mean 69˚K above the non-radiative, rather than the 33˚K assumed by IPCC science. These are intended to represent typical rather than full global calculations. The mean for the condensing atmosphere, at 287˚K, is just 1˚K lower than the commonly accepted global mean of 288˚K.

Figure 9: Measured lunar temperature cycle compared with a hypothetical insulating surface (* values) and emitted radiation

We can go beyond theory. The moon provides a clear and simple empirical example. NASA's 2009 DIVINER lunar temperature data (5) has shown that heat storage in surface rock raises the mean temperature to 217˚K above the 162˚K mean calculated for a thermally insulating surface, giving a DSE of 55˚K. Without this heat storage the night temperature would drop to near the temperature of space, said to be 3˚K. It clearly doesn't. The mismatch between measurements and the OCM model are discussed in note (C).