Sensitivity studies using a climate thermodynamic model, With particular reference to the effect of changing the solar constant

Abstract

The author's thermodynamic model is applied to study the effect of changes in the solar constant on the climate of the Earth. Time steps of one month are used which take into account seasonal variations of the insolation. The horizontal extent of snow-ice and cloud covers are included as variables. After 4 o r 5 years of integration the solution reaches a steady state, which is the one used to evaluate the effect of the changes in the solar constant.
According to the computations, a decrease of 2 percent in the present solar constant produces negative anomalies in the surface temperature , which are stronger in July than in January . The effect of the distribution of continents and oceans appears in the solution, especially in July. The largest anomalies are obtained in July over the continents reaching values of -5.1 degrees Celsius at latitude 30° over America and -6.0 degrees at latitude 20° over Asia. The zonally averaged values of the decrease of surface temperature due to a decrease of 2 percent in the solar constant, in July varying from 2.3° C in lower latitudes to 1.0° C in higher latitudes, and in January varying from 1.7° in lower latitudes to 0.5° C in higher latitudes. Furthermore, it is shown that a decrease of 2 or 4 percent in the solar constant does not produce a substantial increase in the position of the snow and ice boundary. The anomalies in the cloud cover, that appear due to the decrease in the solar constant, have a strong influence in the surface temperatura decrease especially in lower latitudes. The solutions show that it is essential in any climate model to include cloudiness as a variable.
The computed annual average value of the change in the surface temperature due to a decrease of one percent is equal to 0.7° C. A comparison with the results obtained by other authors and models is carried out.