1.The Ozone ShieldSection 13.2
Objectives:
Explain how the ozone layer shields the Earth from much of the sun’s harmful radiation.
Describe the damaging effects of ultraviolet radiation.
Explain why the threat to the ozone layer is still continuing today.
2.The Ozone Layer:
An area in the stratosphere where ozone is highly concentrated
Absorbs most of the UV light from the sun
Acts like a sunscreen for Earth’s inhabitants
3.Chlorofluorocarbons (CFC’s):
Are nonpoisonous, nonflammable, and non-corrosive
Were used as coolants in refrigerators and air conditioners
Also used as propellants in spray cans
Under ideal conditions, 1 chlorine atom can destroy 100,000 ozone molecules
4.The Ozone Hole:
A thinning of stratospheric ozone that occurs over the poles in the spring
5.Effects of Ozone Thinning
6.Protecting the Ozone Layer
1987 – Montreal Protocol – nations agreed to limit production of CFC’s
1992 – developed countries agreed to eliminate most CFC’s by 1995
Ozone depletion continues because CFC’s remain active in the stratosphere for 60-120 years