The cause of ozone depletion is the presence of chlorofluorocarbon compounds which break down due to UV light, producing chlorine radicals which in turn break down the ozone catalytically. Such ozone destruction can take place in the gas phase, but occurs particularly rapidly on the surface of polar stratospheric clouds (PSCs), which form over the poles (particularly the south pole) during winter. Chemical reactions on polar staratospheric clouds (PSCs) in the cold Antarctic stratosphere causes faster depletion .The PSCs only form in extreme cold
Also, the Arctic ozone reduction has been significantly weaker than that of the Antarctic. This may be due to the fact that mean winter temperatures in the Arctic are higher than in the Antarctic, the abundance of polar stratospheric clouds is lower, and the vortex is more variable and breaks down earlier in the winter than in the Southern Hemisphere.