Transcript The Ozone Hole - William Maelia

The Ozone Hole
The Ozone Layer
• Stratospheric ozone
• Block 95% harmful UV radiation
http://svs.gsfc.nasa.gov/goto?824
ODC: Ozone Depleting Chemicals
• CFC’s: Chlorofluorocarbons
– Stable, odorless, nonflammable, nontoxic,
noncorrosive
– Coolants, propellants, cleaners, fumigants, insulation
• Halons (bromine, fluorine)
– Fire extinguishers
– Solvents
– Fumigants
Rowland and Molina:
Groundbreaking Study 1974
• CFC’s remain in troposphere (65 – 385 years)
• CFC’s are heavier than air, but are carried to
the stratosphere by convection and turbulence
• CFC molecules break down with high energy
input from UV radiation
• Chlorine molecules break apart ozone
http://svs.gsfc.nasa.gov/goto?825
The Ozone Hole:
Discovered 1984
• Ozone thinning, NOT ozone “hole”
• Occurs over Antarctica during spring (Aug – Nov)
http://svs.gsfc.nasa.gov/goto?3303
Impacts of Ozone Depletion
• Human Health
– Skin cancer, sunburns, eye cataracts
• Reduced primary productivity in the ocean (kills
plankton, algae)
– Impacts on food web and CO2
• Potential damage to food crops
• Degradation of materials (paints and plastics)
Management:
The Montreal Protocol, 1987
• International agreement
• Eliminate CFC production (goal)
– By 1995 in developed nations
– By 2000 in developing nations
• Assessment of Effectiveness:
– ODC’s will return to pre-1980 levels by 2050
– Ozone “hole” is shrinking!!!