The document discusses ozone layer depletion caused by CFCs and other chemicals. It provides background on the ozone layer's importance for life on Earth and describes how scientists in the 1970s discovered that CFCs were depleting the ozone layer. The Montreal Protocol of 1987 was successful in phasing out CFCs and other ozone-depleting substances to repair the ozone layer by 2050.
2. Ozone Layer Facts...
Ozone Layer Depletion
•
Lower stratosphere (above troposphere)
•
Allows life to exist on Earth
•
Serves as UV filter: 95% of harmful rays
•
Without it: increased risk of cataracts,
sunburn, skin cancer
3. A Closer Look at the causes of
depletion
Depletion Caused By:
•
CFC’s, Halons, Bromine
•
CFC’s: Tom Midgely, GM chemist
•
Uses: refrigerants, propellants,
cleaners, fumigants, blowing agents
for Styrofoam
•
Inactive, easy to make, $28 billion
industry: duPont lead producer at the
time
4. How was the damage
discovered?
•
Sherwood Rowland and Mario
Molina in the 1970’s
•
Investigated years of atmospheric
data rejected by computers
•
Shocked scientific community & the
public
•
Powerful lobby against them
5. Some Atmospheric
Formation of Ozone Chemistry...
O2 + UV light ‐> 2 O
O + O2 + M ‐> O3 + M (where M
indicates conservation of energy
and momentum)
Anthropogenic Destruction of
Ozone by CFC’s
Cl + O3 ‐> ClO + O2
ClO + O ‐> Cl + O2
6. Polar Vortex and The
Cause of Antarctic
Hole
•
1984 Satellite data: 40-50% of Antarctic ozone lost
during spring and summer.
•
Polar vortex. Dark, frigid winter months: strong winds
create swirling masses of air in stratosphere.
•
Winds create suspended microscopic ice crystals that
serve as templates for CFC’s to catalyze breakdown of
ozone.
Polar Vortex
•
Similar, but less dramatic in Arctic.
7. Montreal Protocol of 1987
• Identified CFC’s for elimination first
• Less harmful HCFC’s and HFC’s later
• Bromine, Halons, Fumigants
• Multinational Fund
• Significant repair of ozone layer: 2050
8. The Larger Questions...
• Why was the Montreal Protocol so
successful?
• Why has the Kyoto Protocol been less
successful?
• Where is the line dividing economic
prosperity and the environment?
