Atmospheric CO₂: Global Change and Regulation Mechanisms

Abstract

Abstract For the estimate of the distribution in the carbon system of the CO 2 emitted into the atmosphere due to human activities, the exchange of carbon between atmosphere and ocean, and between atmosphere and biosphere needs to be considered. Information on this spreading of excess CO 2 can be obtained from measurements of a.o. CO 2 , 13 C/ 12 C, 14 C/C in the atmosphere, of natural and nuclear weapon produced 14 C in the ocean and in the biota and of other natural or anthropogenic tracers. — Based essentially on such information, models for the CO 2 uptake by the carbon system have been developed which are capable of reproducing the result of the drop in the rate of increase of CO 2 emissions from 4.5% to 2% per year following the oil‐embargo in 1973. — Of special interest regarding the understanding of the carbon cycle and its role in controlling the climate of the Earth are the observations in polar ice cores covering the past 160.000 years, corresponding to one and a half glaciation cycles. They show variations of atmospheric CO 2 , CH 4 and N 2 O parallel to the climatic variations. Measurements of 13 C/ 12 C in shells of foraminiferas support the hypothesis that these CO 2 changes are caused by changes in the ocean's biological pump, i.e. the flux of detrital organic carbon from the surface to the deep ocean, which affects the total inorganic carbon in the surface ocean and the partial pressure of CO 2 .