AbstractIt is shown that the inclusion of a chlorine chemistry mechanism, necessitated by present abundances of methyl chloride and carbon tetrachloride, reduces the modelled natural stratospheric ozone above about 25 km by 20 to 40% compared with part I, resulting in substantial agreement with observations. The effects of simultaneous increases in the atmospheric mixing ratios of carbon dioxide and chlorofluoromethanes (CFMs) are investigated. It is found that there is alleviation of the CFM‐induced ozone reductions attributable to increased CO2, and that the effects of the two perturbations upon ozone column density are not quite linearly additive. The net effect on ozone column density consists of larger percentage decreases in the upper stratosphere almost compensated by smaller percentage increases in the lower stratosphere, where most of the ozone is residen