PREDICTION OF C0 2 IN THE ATMOSPHERE 



LESTER MACHTA 



Air Resources Laboratories, National Oceanic and Atmospheric Administration, 

 Silver Spring, Maryland 



ABSTRACT 



Predictions of future and past carbon dioxide concentrations have been derived from a 

 simple multireservoir exchange model: stratosphere, troposphere; mixed layer of the ocean, 

 deep ocean; short-term land biosphere, long-term land biosphere, and marine biosphere. All 

 exchanges are prescribed from literature or personal estimates except the troposphere- 

 mixed ocean layer that is obtained from a trial-and-error procedure using bomb ] 4 C0 2 as a 

 tracer. On the basis of reasonable estimates of growth in the use of fossil fuel, the 

 atmospheric C0 2 content predicted for the year 2000 is about 385 ppM, compared to about 

 320 ppM observed at present. The uncertainties in the model are probably less significant 

 using the above-mentioned procedure than the assumption that the oceans and biosphere 

 will continue to behave in the future as in the 1960s. The so-called greenhouse effect, using 

 a simplified one-dimensional (vertical) model of the atmosphere, calls for about a 0.5°C 

 warming from the increase of C0 2 to 385 ppM. But this estimate of 0.5°C is on even shakier 

 grounds than the forecast of future C0 2 concentrations. 



This paper is offered from the viewpoint of a meteorologist concerned with 

 predicting the possible future climatic change due to the increase of carbon 

 dioxide in the atmosphere. There are two aspects of this climatic prediction. 

 First, the fate of the added C0 2 in future years and second, the possible climatic 

 change from atmospheric increases. We shall primarily discuss the first of these 

 topics and touch only lightly on the second. Future C0 2 in the air depends on 

 two factors: first, the added fossil-fuel carbon dioxide injected into the air and, 

 second, the apportioning of this carbon dioxide between the atmosphere and the 

 reservoirs with which it can exchange. 



Dr. Ekdahl, in his paper, discusses in much greater detail the observed data 

 for the growth of carbon dioxide in the atmosphere at Mauna Loa and the South 

 Pole. Other data, such as those collected by Bischof 1 in Sweden and by the 

 National Oceanic and Atmospheric Administration aboard Ocean Weather Ship 



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