ATMOSPHERIC CARBON DIOXIDE AND RADIOCARBON: I 



71 



< 



CO 

 < 

 I 

 Q. 



180 



120 - 



60 



10 



100 1000 



PERIOD, years 



10,000 



100,000 



Fig. 14 Predicted attenuation and phase shift of ' 4 C in the lower atmosphere 

 relative to an oscillating source in the upper atmosphere as a function of 

 oscillation period. Predictions are given for three models: single reservoir 

 model with reff = 100 years (-curve); five-reservoir model (--curve); 

 six -reservoir model (full curve). Also shown (- - - curve) are the salient features 

 of the 11- and 85-year bands in the sunspot spectrum. The five- and 

 six-reservoir calculations are for the standard case given in Table 1. 



model in which the stratosphere and lower atmosphere are not separated 

 (Fig. 14). Except for the phase shift at high frequencies, the five- and 

 six-reservoir cases differ only slightly. Both, however, predict attenuations 

 roughly four times as great as those of Grey and Damon at the frequencies of 

 interest. These higher attenuations, already found for a series of two- and 



three-reservoir models by Houtermans, significantly weaken the correlation 

 between the predicted and observed atmospheric C trend since 1700. The 

 attenuation is sensitive principally to the parameters characterizing the air— sea 

 interface. Even unrealistically large changes in the size of the land biota or the 

 deep-ocean-to-surface-layer transfer time have little effect in the frequency range 

 of interest (see Figs. 15 to 18). In no realistic case does a prediction approach 

 that of the one-reservoir model. Unless the heliomagnetic ' 4 C variation is several 

 times larger than assumed on the basis of Lingenfelter's 1 study of cosmic-ray 

 data, the prediction of Grey and Damon 2 : ' greatly exaggerates the variation in 

 atmospheric 14 C0 2 which can take place in direct correlation with sunspots. 



