Figure 16 – Atmospheric compositional variations throughout the last 200 years as deduced from analyses of trapped gases in Antarctic ice. The records show the rapid accumulation of three trace gas species in the atmosphere, largely the result of increased emissions of these gases, which relate to increased world population (McEvedy and Jones, 1978). Also included are records of direct measurements, which started in 1957 (Keeling et al., 1976). Data taken from Etheridge et al. (1992, 1996) for CO2 and CH4, and Machida et al. (1995) for N2O.