Some of the sun's UV rays can be absorbed by the Earth's surface or bound back off. Although this would be a "good" thing, it is not. These very rays cause the ozone layer to deplete over long periods of time from the rays "breaking it.
Decline in Antarctic Ozone Depletion and Lower Stratospheric Chlorine Determined From Aura Microwave Limb Sounder Observations
New Study Showing Ozone Recovery Hailed as Model for Tackling Climate Crisis: "We see very clearly that chlorine from CFCs is going down in the ozone hole and that less ozone depletion is occurring because of it."
Image above: View of the South Pole from NASA's TOMS (Total Ozone Mapping Spectrometer) satellite. Blue and green indicate relatively large amounts of ozone. Red and yellow mark the "ozone hole," an area of decreased ozone.