1. Stratospheric Ozone

2. Ozone Layer
Not really a layer: region of higher-than- normal ozone concentrations
~17 km-30 km altitude
Absorbs ultraviolet (UV) radiation from sun, protecting organisms on surface from radiation damage

3. How Have We Depleted Ozone in the Stratosphere & What Can We Do?
Noticed in 1980s
Widespread use of certain chemicals has:
Reduced ozone levels in the stratosphere
Allowed more harmful ultraviolet radiation to reach the earth’s surface
To reverse ozone depletion:
Stop producing ozone-depleting chemicals
Adhere to the international treaties that ban such chemicals

4. Information about Ozone Depletion
Characterized as a rapid depletion of ozone over Antarctica during spring.
Ozone hole season, Spring (August – October)
Ozone hole located over mainly over Antarctica.
Ozone hole recovers by late December
Ozone hole not present in early 1970’s

5. Our Use of Certain Chemicals Threatens the Ozone Layer
Ozone is thinning over Antarctica and the Arctic
Chlorofluorocarbons (CFCs)
Persistent chemicals that attack ozone in the stratosphere
Mass-produced by industry, in refrigerants & consumer products like aerosol sprays
Other chemicals: Hydrobromoflurocarbons (HBFCs), Methyl bromide, Hydrogen chloride, Carbon tetrachloride, methyl chloroform, n-propyl bromide, hexachlorobutadiene

6. Ozone equations Formation of ozone:
O + O2 O3
Ozone depletion: CFCs split oxygen atoms to form (O2)

7. How do CFCs Break Down Ozone?
CFCs and others released into troposphere
CFCs move/drift upward into stratosphere
UV radiation breaks apart CFCs releasing chlorine (bromine/fluorine)
Sunlight causes chemical reaction allowing Cl to attack O3, creating O2

8. Montreal Protocol-An Environmental Success Story
1987, 36 initial nations
Over 180 nations signed Montreal Protocol (including US) (during the Copenhagen Protocol: Amendment)
Restricted CFC production globally
Today: ozone holes are starting to recover
Reasons for success:
Government and industry cooperated on finding solutions
Implemented with adaptive management: ability to fine-tune actions

9. Why Should We Worry About Ozone Depletion?
Ozone protects the earth’s surface from damaging UV radiation
Human health concerns
UV radiation affects plankton (impairs/destroys)
Disrupts food chains
Damages fish/amphibians/mammals
Widespread effects on major food crops
Decrease plant productivity
We can reverse it by: stop producing ozone-depleting chemicals immediately
Agreements with a prevention approach:
Montreal Protocol
Cut emissions of CFCs
Copenhagen Amendment
Accelerated phase- out

10. The Chemicals Don’t Just Disappear…
Worst ozone depletion: projected between and 2019.