Two recent studies indicate that the Montreal Protocol, a 1987 treaty designed to protect the eroded stratospheric ozone layer, is finally beginning to work. Because it takes time for harmful chemicals to migrate up through the atmosphere to sensitive ozone layers, scientists are only now able to measure the effects of reductions begun in 1987. " Increases in the concentration of chlorine, the ozone destroyer in CFCs, have begun to slow in the upper stratosphere. Newchurch attributes this improvement to the global ban on CFCs, compounds once widely used in aerosols and refrigerants.
Source: Chafe, Zoe, "Ozone layer making tentative improvements," World Watch, Vol. 16, No. 6, November/December 2003, 8.