Representative data on the variations of carbon dioxide in the atmosphere are presented. The data reveal a presumably natural source in the tropical oceanic areas and the industrial source of midlatitudes. Using a simple model of large-scale exchange, the meridional eddy exchange coefficient is computed to be about 3×1010 cm2 sec−1, and the meridional transport from tropical to north polar areas is computed to be about 2×1010 metric tons of carbon dioxide per year. An analysis of the seasonal variation shows that land vegetation north of 45°N is responsible for a net consumption of carbon dioxide of about 1.5×1010 tons during the vegetation period in summer. It is concluded that carbon dioxide is an excellent tracer for the study of atmospheric mixing processes. More data are needed, however, to make full use of it.