Ozone: The “HOLE” Story

Stratospheric Ozone “Good” Ozone (O3) Blocks 95% of ultraviolet (UV) radiation from reaching Earth’s surface Considerable seasonal thinning over Antarctica and Arctic

Satellite Image

What is the cause? Chloroflourocarbons, aka CFC’s or freons Unreactive, odorless, nonflammable, nontoxic, noncorrosive, inexpensive = DREAM CHEMICALS Used as coolants in air conditioners, refrigerants, aerosol spray cans, styrofoam, etc. Too good to be true?

YES!! 1974 – Rowland & Molina – CFC’s (along with other ODC’S) destroy ozone! Called for an immediate ban Major conclusions: 1. Persistent 2. Take 11-20 years to reach stratosphere 3. Break down under high-energy UV radiation releasing Cl which “attacks” ozone

HOW?

What time of year? Typically, the “hole” appears in Antarctica during Spring (Sep, Oct. & Nov) Why? During long, cold, dark winter – strong winds create ice crystals at high altitudes Ozone & chlorine containing molecules build up on ice Sun reappears after a long winter and “liberates” the Cl – begins “attack”

So, what happens then? Human Health: Food & forests: Wildlife: Worse sunburns More eye cataracts Increased skin cancer Immune system suppression Food & forests: Reduced crop yields Decreased forest productivity Wildlife: Decreased pops. of sensitive species Reduced phytoplankton (affect food webs)

We can reverse this! Stop using ODC’s (still lag time) MONTREAL PROTOCOL (1987) Cut emissions of CFC’s by 35% b/t 1989-2000 If nations follow, could return to pre-1980 levels by 2068 O3 can naturally replenish itself