Figure 4.

Time series of simulated annual mean total stratospheric chlorine from VSLS (sum of source and product gas contributions, filled circles, left axis). A linear trend line is applied to EXP2 which considered CH₂Cl₂, CHCl₃, and C₂Cl₄, and the 2005–2013 mean growth rate (ppt Cl⁻¹) is annotated. EXP3 (blue) also considered C₂HCl₃ and CH₂ClCH₂Cl. Also overlaid are annual mean CH₂Cl₂ mixing ratios (ppt) in the Northern Hemisphere calculated from NOAA surface observations (red crosses, right axis).