Atmospheric carbontetrafluoride (CF4): Sources and trends

Concentrations of carbontetrafluoride (CF 4 ) observed at the south pole suggest that this inert trace gas is accumulating in the earth's atmosphere at about 1.3 (0.8‐2) pptv/yr. This amounts to an average increase of about 1.8 (1‐3) × 10 10 gms/yr and can be explained by the estimated emissions of CF 4 from aluminum manufacturing. Although it is still not possible to determine how much, if any, of the present atmospheric content of CF 4 is from natural sources, it appears that these sources are small (≦10 9 gm/yr) and therefore will be extremely difficult to identify and evaluate.