The depletion of the ozone layer is caused mainly by the increase in emissions of chlorine- and bromine-containing compounds like CFCs, halons, carbon tetrachloride, methyl chloroform and methyl bromide. Emissions of greenhouse gases can affect the depletion of the ozone layer through atmospheric interaction.
We studied the interactions in the atmosphere between the greenhouse effect and stratospheric ozone depletion from the point of view of past and future emissions of the anthropogenic compounds: CFCs, halons, CH4, N2O, NOx, CO and CO2. In our investigation the increase in emissions of chlorine- and bromine-containing compounds, largely responsible for the depletion of stratospheric ozone at mid-latitudes, was found to be -5.8% per decade from 1980 to 1990.
The increase in CH4 emissions in the same period changes this ozone depletion by +1.4% per decade to -4.4% per decade, which is close to TOMS and Dobson measurements. The increase in N2O emissions hardly affects this depletion. The decrease in stratospheric temperatures due to increased CO2 emissions also diminishes the ozone depletion ; the same may also happen when NOx emissions are increased. The effect of these interactions in coming decades is to accelerate the recovery of the ozone layer.
The trend in CH4 emissions described in the business-as-usual scenario IS92a may yield 1980 ozone column levels in 2060 compared with 2080 with CH4 emissions fixed at 1990 levels. The temperature decrease in the stratosphere may initially also accelerate the recovery of the ozone layer by several years, ignoring a possible large extra ozone depletion by the extra formation of polar stratospheric clouds over large areas of the world.