1. The Ozone Shield
Unit 2: The Atmosphere

2. What is it?
Ozone layer – area in the atmosphere where ozone is highly concentrated
Absorbs most of the UV light from the sun
UV radiation damages genetic material in living cells (acts like a sunscreen)
Made up of three Oxygen atoms
When is radiation good?

3. Chlorofluorocarbons (CFCs)
Miracle chemicals
Nonpoisonous, non flammable, do not corrode metals
Used as coolants in refrigerators and air conditioners
Also as a “fizz” for making plastics foams and a propellant in aerosol cans
Stable at Earth’s surface, but are not so in the atmosphere and breakdown Ozone (1970s – shocking)
Single chlorine atom can destroy as many as 100,000 ozone molecules! (more on this later)

4. The Ozone Hole
In 1985, an article in Nature reported the ozone layer had thinned by 50-98%!
During the winter (very cold temperatures), chlorine is separated from CFCs on the surface of a special type of high-altitude clouds
When the temperature warms in the spring UV radiation splits chlorine which begins to destroy ozone
Satellites had observed this as early as 1978

5. Why does it look like it’s not getting any bigger?

6. Effects on/of Living Things
So if ozone is an air pollutant, why can’t we just produce more?
Less ozone means more UV radiation – lather on the sunscreen!
Can kill phytoplankton on the surface of the ocean
Disrupts the food chain – why?
Increased carbon dioxide
Amphibians that lay eggs in shallow
water also especially susceptible
(and “good” indicators)

7. Protecting the Ozone Layer
Montreal protocol – countries around the world agreed to limit their production of CFCs
U.S. pledged to ban all substances by 2000
International success story – kind of
CFCs last a very long time ( years)
Developing countries are actually increasing their production of them