Global climate change: an investigation of atmospheric feedback mechanisms

Abstract

A global energy balance for the earth-atmosphere system requires knowledge of a number of quantities, two of which are tropospheric lapse rate and cloud altitude. Since both of these quantities could be dependent upon surface temperature, they are potential candidates for feedback mechanisms in surface-temperature sensitivity studies. The present investigation illustrates that the global energy balance is quite insensitive to lapse rate, thus eliminating this as a possible feedback mechanism. Cloud altitude, on the other hand, can be quite important. Employing a three-layer cloud model, and comparing calculated and empirical outgoing flux results, it is suggested that cloud temperatures should be held constant when considering variations in surface temperature, as opposed to the conventional assumption of fixed cloud altitudes. This is consistent with earlier single-cloud modeling (Cess, 1974), and based upon this conclusion it is found that the resulting dependence of cloud altitude upon surface temperature produces a strong positive feedback.