Figure 4.6. Index of global emissions of sulphur dioxide, nitrogen oxide, and carbon dioxide.

Alcamo and Kreileman (1996); Gschwandtner et al. (1985); Hameed and Dignon (1988); Keeling (1973, 1994); Klein Goldewijk and Battjes (1995); Marland and Rotty (1984); Marland et al. (1994); Mylona (1993); Overrein et al. (1981); Placet and Streets (1987); WRI/UNEP/UNDP (1994).
Data for carbon dioxide emissions before 1990 are derived from Keeling (1994); data after 1990 are assumed and are from Posch et al. (1996). No reliable historical data are available for nitrogen oxide emissions.