Percentage change in global ozone predictions with and without compliance with the Montreal Protocol, an international agreement which phases out CFC production by 2000. The Montreal Protocol was signed in 1987 and has since been strengthened. Without the Montreal Protocol, we would be looking at a disastrous reduction in ozone levels. Summary Various greenhouse gases are accumulating in the atmosphere due to human activities, these include CFCs, N 2 O, methane and CO 2 . Some of these gases also affect stratospheric ozone concentrations.
Ozone depletions occur when catalytic chemistry accelerates natural loss processes.
An important catalytic loss reaction chain involves chlorine, made available in the stratosphere by the photolysis of CFCs. One such problem involves increases in skin cancer. Links Send feedback to the Global Change Webmaster .