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!!!