Ozone Depletion in the Stratosphere

Overview of Ozone Depletion

2000 – hole reached 11.3 million square miles Stratospheric ozone thinning first observed –1985 - scientistis working in Antarctica - Article in Nature reported the results – Ozone levels over Antactic had thinned by 50 – 98%! 2000 – hole reached 11.3 million square miles

Stratospheric ozone thinning over the Arctic

1995 – First Nobel Prize in Env. Sci 1995 – First Nobel Prize in Env. Sci. awarded for connecting the ozone hole to CFC. 1996 – CFCs were phased out in the U.S. October 2007 

Causes of Ozone Depletion Chlorine or Bromine Compounds Chlorofluorocarbons (CFC) - nonpoisonous, nonflammable, & non-corrosive. - Propellants for aerosol cans - Coolants in A.C. & refigerators (Ex: Freon) - Foam-blowers (EX: styrofoam) - Industrial solvents - Fire retardants

Return of sunlight to polar region Circumpolar vortex Thinning is worst between September & November (spring in S. Hemisphere) for 2 reasons… Return of sunlight to polar region Circumpolar vortex

Effects of Ozone Depletion High UV Exposure leads to Eye cataracts Skin cancer Weakened Immunity Disruption of Ecosystems Antarctic food web DNA mutations in fish Damage to crops & forest Decline in amphibian populations

Facilitating the Recovery of the Ozone Layer Montreal Protocol – international agreement to reduce CFCs by 50% (1998) - modified to have stricter regulations CFC substitutes - Hydrofluorocarbons (HFCs)  does not thin ozone, but is a greenhouse gas - Hydrochlorofluorocarbons (HCFCs) CFC leaking out of old refrigerators & A.C. CFC smuggling – black market