The Ozone Hole. The Ozone Layer Stratospheric ozone Block 95% harmful UV radiation .
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Transcript of The Ozone Hole. The Ozone Layer Stratospheric ozone Block 95% harmful UV radiation .
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The Ozone Hole
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The Ozone Layer
• Stratospheric ozone• Block 95% harmful UV radiation
http://svs.gsfc.nasa.gov/goto?824
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ODC: Ozone Depleting Chemicals• CFC’s: Chlorofluorocarbons
– Stable, odorless, nonflammable, nontoxic, noncorrosive
– Coolants, propellants, cleaners, fumigants, insulation
• Halons (bromine, fluorine)– Fire extinguishers– Solvents– Fumigants
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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
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The Ozone Hole: Discovered 1984
• Ozone thinning, NOT ozone “hole”• Occurs over Antarctica during spring (Aug –
Nov)
http://svs.gsfc.nasa.gov/goto?3303
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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)
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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!!!