90 



BACASTOW AND KEELllMU 



3600 



2800 — 



CD 

 > 



CM 



*o 

 Z 2000 



o 

 en 



rr 

 < 



£ 1200 



Z) 

 Q 



400 



1 1 1 1 ' 1 r ' ' VT~*~ 



I • 

 / • 



/ • 

 / • 



/ • 



/ • 



i • 



i • 



* • 



I m 



I • 



/ • 



/ • 

 / • 



/ • 



/^ • 



y m 



S m 



/ •••• 



/ • • • 



/ • • * 



. — ..••••• 



1860 



1880 



1900 



1920 

 YEAR 



1940 



1960 



Fig. 2 Industrial carbon dioxide production since 1860. The solid curve is an 

 exponential function with a growth of about 3% per year used by Bolin and 

 Eriksson 3 in their model. 



backward from 1860 to 1700. For projections beyond 1970, a 4% growth rate in 

 yearly industrial COt was assumed. The recalculated annual values of Keeling for 

 CO2 production are about 13% lower than those of Revelle 1 and of the Study 

 of Critical Environmental Problems 5 because delayed or incomplete 

 combustion is taken into account and because the carbon content of lignite was 

 overestimated in the earlier studies. Keeling 13 estimates that systematic errors 

 contribute about ±15% uncertainty to the recalculated production data. 



ATMOSPHERIC CARBON DIOXIDE 



Accurate direct observations of atmospheric CO2 are available for approxi- 

 mately the past 15 years. The longest and most continuous records, 7 obtained at 

 Hawaii and the South Pole, indicate for 1959 to 1969 an atmospheric C0 2 

 increase of 2.34% ± 0.20 relative to preindustrial times, and an airborne fraction 

 of industrial C0 2 of 49% ±12. Over half the uncertainty in the airborne fraction 

 is related to the estimation of industrial C0 2 production. 



