A Simple Alternative Model for the Estimation of the Carbon Dioxide Effect on the Earth's Energy Balance

Abstract

A simple model for the evaluation of the CO2 concentration effect on the radiative component of the Earth's energy balance is described. The model calculates a single parameter, an expected increase of the average temperature at the Earth surface caused by doubling the CO2 concentration in the atmosphere. The model is based on the spectrum of Planck radiation leaving the Earth's surface and on IR spectral characteristics of the air column above the surface. The principal distinction of the model with respect to comprehensive global general-circulation models is the representation of the atmosphere as a combination of narrow-range IR filters. Within the approximations used in the model, a doubling the CO2 concentration in the Earth's atmosphere would lead to an increase of the surface temperature by about +0.5 to 0.7 °C, hardly an effect calling for immediate drastic changes in the planet's energy policies. An increase in the absolute air humidity caused by doubling the CO2 concentration and the resulting decrease of the outgoing IR flux would produce a relatively small additional effect due to a strong overlap of IR spectral bands of CO2 and H2O, the two compounds primarily responsible for the greenhouse properties of the atmosphere.