The Erythemal Index is a measure of ultraviolet radiation (UV) at ground level on the Earth. UV exists to the left of the visible spectrum and is divided into three components (UV-A, UV-B and UV-C). UV-B (290-320 wavelengths) is the most dangerous form of UV radiation that can reach ground level. Atmospheric ozone shields life at the surface from most of the harmful components of solar radiation. Chemical processes in the atmosphere can effect the level of protection provided by the ozone in the upper atmosphere. This thinning of the atmospheric ozone in the stratosphere leads to elevated levels of UV-B at ground level and increases the risks of DNA damage in living organisms.
This erythemal index for Europe and Africa shows the range of ground levels of UV radiation from the highest (in red) to the lowest (in purple). This animation shows the fluctuation with the red areas moving from the equatorial region, Southward, then back to the middle as time passes from August, 2000 to July, 2001.