Ozone is discussed on two different levels - stratospheric ozone and ground level ozone .
Stratospheric ozone makes up a layer in the sky above the earth that absorbs most of the ultraviolet radiation from the sun. This ozone layer is sometimes called the ozonosphere. Destruction of this shield by certain human-made chemicals allows more ultraviolet radiation to reach the earth's surface. The sun's rays convert these emissions into ground level ozone. Cars and gasoline-burning engines are large sources of emissions.