Carbon Dioxide Exchange Between Atmosphere and Ocean and the Question of an Increase of Atmospheric CO, during the Past Decades By ROGER REVELLE and HANS E. SUESS, Scripps Institution of Oceanography, University of California, La Jolla, California (Manuscript received September 4, 1956) Abstract From a comparison of C14/C1sand Cla/C1*ratios in wood and in marine material and from a slight decrease of the C14 concentration in terrestrial plants over the past 50 years it can be concluded that the average lifetime of a CO, molecule in the atmosphere before it is dissolved into the sea is of the order of 10 years. This means that most of the CO, released by artificial fuel combustion since the beginning of the industrial revolution must have been absorbed by the oceans. The increase of atmospheric CO, from this cause is at present small but may become significant during future decades if industrial fuel combustion continues to rise exponentially. Present data on the total amount of C 0 2 in the atmosphere, on the rates and mechanisms of exchange, and on possible fluctuations in terrestrial and marine organic carbon, are inadequate for accurate measurement of future changes in atmospheric COP An opportunity exists during the International Geophysical Year to obtain much of the necessary information. Introduction In the middle of the 19th century appreciable amounts of carbon dioxide began to be added to the atmosphere through the combustion of fossil fuels. The rate of combustion has continually increased so that at the present time the annual increment from this source is nearly 0.4 % of the total atmospheric carbon dioxide. By 1960 the amount added during the past century w ill be more than IS %. CALENDAR (1938, 1940, 1949) believed that nearly all the carbon dioxide produced by fossil fuel combustion has remained in the atmosContribution from the Scripps Institution of Oceanography, New Series, No. goo. This paper represents in part results of research carried out by the University of California under contract with the Ofice of Naval Research. phere, and he suggested that the increase in atmospheric carbon dioxide may account for the observed slight rise of average temperature in northern latitudes during recent decades. He thus revived the hypothesis of T. C . CHAMBERLIN (1899)and S. ARRHENIUS (1903) that climatic changes may be related to fluctuations in the oarbon dioxide content of the air. These authors supposed that an increase of carbon dioxide in the up er atmosphere would lower the mean level o back radiation in the infrared and thereby increase the average temperature near the earth's surface. Subsequently, other authors have questioned Callendar's conclusions on two grounds. First, comparison of measurements made in the 19th century and in recent years do not demonstrate that there has been a significant increase in P Tellur IX (1957). 1