2. The Ozone Shield Atmosphere and Climate Change Chapter Thirteen Section Two

3. The Ozone Shield  Ozone layer – part of stratosphere where ozone is concentrated  Absorbs most of the harmful ultraviolet (UV) rays from the sun  UV rays damage genetic material  Ozone layer being damaged by chlorofluorocarbons or CFCs

4. Chlorofluorocarbons  Nonpoisonous, nonflammable, noncorrosive  Used as coolant in freezers and AC, to make plastic, in spray cans & pesticides  Stable at Earth’s surface  In stratosphere, CFCs broken apart by UV rays  Parts of CFC destroys protective ozone layer

5. The Ozone Hole  Thinning of stratosphere that occurs over the poles in the spring  In 1985, studies showed the ozone layer over the South Pole had thinned by over 50%  Polar stratospheric clouds make air very cold which leads to breakdown of CFC  When sun returns, energy drives destruction of Ozone

6. Effects of Ozone Thinning  On Humans – As ozone decreases, UV rays reaching Earth increases  UV rays damage DNA in humans  On Animals & Plants – high UV rays can kill phytoplankton, harm amphibians, interfere with photosynthesis

7. Protecting the Ozone Layer  1985 Montreal Protocol led to agreement to limit CFCs  In 1995, developed nations pledged to ban CFCs completely  CFC use has dropped dramatically from over 1,000 millions tons per year to less than 200 million tons per year  CFCs stay in stratosphere 60 to 120 years