ATMOSPHERIC CARBON DIOXIDE AND RADIOCARBON: II 



101 



-1.2 



Q 



< 



D 



< 

 H 

 CO 



> 

 < 



co -2.0 



CO 



-1.6 — 



N mo /N ao = 12 



-2.4 



n 



o 



2 3 4 



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



Fig. 5 Adjustment of the six-reservoir model to predict a given Suess effect 

 relative to standard Su 4g , or a given C0 2 increase in the atmosphere 

 between 1959 and 1969. One curve was obtained by varying the deep-ocean to 

 surface-layer transfer time, r^ m ; the other curve was obtained by varying 

 N mo /N ao , the ratio of preindustrial carbon in the ocean surface layer to that 

 in the atmosphere. If not varied, T^ m was 1500 years and N mo /N ao was 2. 

 The atmosphere— ocean transfer time, r am , was 6 years, and the biota was held 

 to a constant size (/3 = 0). 



conditions), compared with -2.1% (-2.8% in 1954) obtained from recent data. 

 Indeed, to predict the observed Su 48 exactly requires N m0 /N a0 less than 2 or 

 Tj m greater than 1500, in total disregard for the shorter circulation time of the 

 intermediate water relative to deep water. Thus our attempt to reconcile the 

 model predictions with both the observed Suess effect and the recent 

 atmospheric C0 2 increase results in conflicting demands. The former suggests a 

 surface layer that is too small; the latter suggests one that is too large. 



The only means the model affords to reconcile the second discrepancy is to 

 assume an increase in carbon stored in the land biota. We are aware that many 

 biologists believe the land biota to be static or shrinking because of the 

 destruction of forests and humus. The land biota is, nevertheless, a very complex 

 system; a few percent increase could not be directly observed. 



The most important consequences of postulating a positive biota growth 

 factor can be deduced from Fig. 6 and Table 2. The curves, obtained by 



