T H E Q U E S T I O N OF I N C R E A S E O F A T M O S P H E R I C CO, 25 Fig. 2. Expected secular increase in the CO, concentration of air (7) according to Eq. (7), for average lifetimes of COI in the atmosphere t(atm) = 10years and 3 0 years, with and without correction for the increase in the partial C O , pressure with total C O , concentration of sea water (curves for y = 10 and y = I respectively), for a constant rate of addition of industrial COP of i = 2.5 * 10-*x Ao. for r and s small compared to A, and So respectively. As a reasonable ap roximation we may write instead of Eq. (3f: of CO, production from fossil fuels. However, over a sufficiently long period of time the alkalinity of the ocean must be expected to rise more rapidly as a consequence of the higher total CO, concentration in the atmos here and ocean which will tend to increase e rate of rock weathering and to decrease the rate of de osition of CaCO,. The secular increase in I s o d d therefore be less than that calculated from Eq. (7) with ~ = I O and somewhere between the curves shown in figure 2 for y=Ioandy=I. It seems therefore quite improbable that an increase in the atmospheric CO, concentration of as much as 10 % could have been caused by industrial fuel combustion during the past century, as Calleridar’s statistical analyses indicate. It is possible, however, that such an increase could have taken place as the result of a combination with various other causes. The most obvious ones are the following: I) Increase of the average ocean temperature of I’ C increases Pco, by about 7 %. However, such increase would also raise the sea level by about 60 cm, due to thermal expansion of the ocean water. Actually, according to MUNKand REVELLE (1952),although the sea level has risen about 10 cm during the last century, this rise can be accounted for almost quantitatively by addition of melt water from retreating glaciers and ice caps. The increase in the average ocean temperature is probably not more than 0.05’ C, which corresponds to an increase in PCo, of 0.35 %. In the case of slow oceanic mixin , the increase could be somewhat larger, if oI fy tR or 1 Figure 2 shows r as a function of time calculated from Eq. (7) for two values of k, corresponding to an exchange time of 10 and 3 0 years respectively, assuming constant addition of industrial CO, equal to 0.25 % of the CO, in the atmosphere per year. At present the integrated amount of industrial CO, corresponds to about 40 to 50 years of addition at this constant rate. The increase in CO, in the atmosphere plus biosphere and soil due to industrial fuel combustion should therefore at present amount to 3 to 6 %, depending on the assumptions made with respect to the size of the “effective” atmos heric carbon reservoir that exchanges with t e ocean. Eq. (7) and figure 2 show that addition of industria CO, at a constant rate should eventually lead to a situation in which the secular increase in CO, in the atmosphere plus . . !i biosphere and soil equals __iyk2‘k1 I vk,Ik. - -C ’ ’-z,.-L , per year. With So/Ao=kl/kz = 60 and i=o.zs ,an increase of 3.6 % er century is obtained. We have neglected t e present rate of increase in alkalinity, which is small,compared to the rate K Tellus IX (1957). 1