104 



BACASTOW AND KEELING 



2 3 4 



C0 2 INCREASE (1959 TO 1969), % preindustrial atmosphere 



Fig. 7 Model-acjjustment curves derived as in Fig. 6, except that R m /R # is 

 fixed at 0.978. 



considerations of the intermediate water circulation, 32 the effective value of 

 N m0 /N a0 probably does not exceed 6. With a lower limit on N m0 /N a0 of 2, as 

 discussed earlier, the true value of Su 48 according to Fig. 6 lies between —1.7 

 and -2.0%. 



This prediction, however, takes no account of uncertainties in other model 

 parameters. The curves in Fig. 6 refer to models consistent with a relative C/C 

 ratio in the surface layer, R m /R # , of 0.999 in 1954. If instead we adopt the 

 lower limit of 0.978, we obtain the results shown in Fig. 7. For the same range 

 of N m0 /N a0 , the Suess effect is more negative by about 0.2%. On the other 

 hand, for a given value of N m0 /N a0 , the range in growth factor remains 



