PREDICTION OF CO, IN THE ATMOSPHERE 



29 



200 



300 



400 



500 



600 



700 



ATMOSPHERIC C0 2 , ppMv 



Fig. 5 Surface air-temperature change due to increased atmospheric C0 2 with 

 average cloudiness, assuming a convective-radiation equilibrium and a fixed 

 humidity (adapted from Manabe and Wetherald 6 ). 



There are at least two feedback mechanisms that have so far been omitted in 

 quantitative treatments of climatic changes from increased C0 2 . First, the added 

 moisture may increase the cloudiness. Clouds play a dominant role in controlling 

 the earth's albedo or reflecting power to solar radiation. It has been estimated 

 that the net effect of a global increase of only 0.6% in low cloudiness over the 

 globe will cool the lower atmosphere by the same 0.5 C that the 385 ppM is 

 predicted to warm the lower atmosphere. 8 Thus, if the added warmth and 

 moisture by the so-called greenhouse effect also increase low cloudiness, much 

 of the warming can be negated. 



The second is a positive rather than a negative feedback. If the warming of 

 the lower atmosphere should also warm the surface layers of the waters, 

 additional oceanic C0 2 will be released. This, in turn, would intensify the 

 atmospheric warming and so forth. 



