APPENDIX 371 



Measurements are available from five sources: Swedish flights, Mauna Loa, the 

 Antarctic, 8 Point Barrow, Alaska, 9 and Upton, N. Y. 1 Of these sources, only 

 Mauna Loa is continuous from 1958 to the present, and it is by far our finest 

 record of CO2 change on annual and a longer term basis. These data indicate 

 that atmospheric CO2 has been increasing by 0.2%/year, or 0.7 ppM/year, but 

 that the rate of increase is now about 1.5 ppM/year. 



Measurements of the quality of those on Mauna Loa by the Scripps 

 Institution of Oceanography should be expanded on a latitudinal basis. For 

 short-term monitoring, work group 3 of the SCEP Report (Ref. 1, page 195) 

 recommended four stations including Alaska, Hawaii, a South Indian Ocean 

 island, and Antarctica. For effective research purposes, however, they (and the 

 Brookhaven group) recommend 12 such stations, 9 stretched latitudinally across 

 the Pacific, and 3 extended longitudinally, to examine continental effects vs. 

 marine effects on exchange. Such stations would not only monitor increases in 

 atmospheric C0 2 , but would provide global estimates of net carbon exchanges 

 by the biota with the seasons. The data would aid in appraising the response of 

 the biota to elevated CO2 levels. 



Further details of this proposal can be found in the SCEP Report (Ref. 1, 

 pages 192 to 198) and in the SMIC Report (Ref. 11, page 244). 



The Suess Effect 



Prior to the industrial revolution, normally produced 14 C was incorporated 

 in living systems at fixed concentrations. With an increase of C-poor CO2 in 

 the atmosphere derived from fossil-fuel combustion, the C content decreased 

 proportionately. This dilution of 14 C by fossil-fuel injection is termed the 

 "Suess effect" and is a natural means of extending direct measurements of 

 atmospheric C0 2 increase for periods preceding nuclear testing. With testing, 

 14 C production increased above the natural rate and ! C content of plants 

 increased proportionally. 



The Brookhaven group strongly urged that tree rings of carefully selected 

 trees from around the world be analyzed for the Suess effect by a single 

 laboratory with a single method and standard. A coordinated effort over several 

 laboratories is needed to resolve questions on the period 1850 to 1950 (compare 

 Bacastow and Keeling, this volume). With these data, we will have a firmer grasp 

 on pre-1950 changes in the atmosphere. 



Trace Gases 



There are a number of atmospheric trace gases, such as H 2 , CH4, CO, and 

 N 2 0, whose production is partly or predominantly biotic (Refs. 12 and 13). 

 Their concentrations are normally low, between 0.1 and 1.5 ppM, so that they 

 have little influence on the tropospheric energy budget. However, their 

 atmospheric lifetimes are long enough that they are mixed in considerable 

 amounts into the stratosphere. There they may be of importance because they 



