Ozone Layer Facts...Ozone Layer Depletion •Lower stratosphere (above troposphere) •Allows life to exist on Earth •Serves as UV ﬁlter: 95% of harmful rays •Without it: increased risk of cataracts, sunburn, skin cancer
A Closer Look at the causes of depletionDepletion Caused By: • CFC’s, Halons, Bromine • CFC’s: Tom Midgely, GM chemist • Uses: refrigerants, propellants, cleaners, fumigants, blowing agents for Styrofoam • Inactive, easy to make, $28 billion industry: duPont lead producer at the time
How was the damage discovered?•Sherwood Rowland and Mario Molina in the 1970’s•Investigated years of atmospheric data rejected by computers•Shocked scientiﬁc community & the public•Powerful lobby against them
Some AtmosphericFormation of Ozone Chemistry...O2 + UV light ‐> 2 OO + O2 + M ‐> O3 + M (where M indicates conservation of energy and momentum)Anthropogenic Destruction of Ozone by CFC’sCl + O3 ‐> ClO + O2ClO + O ‐> Cl + O2
Polar Vortex and The Cause of Antarctic Hole • 1984 Satellite data: 40-50% of Antarctic ozone lost during spring and summer. • Polar vortex. Dark, frigid winter months: strong winds create swirling masses of air in stratosphere. • Winds create suspended microscopic ice crystals that serve as templates for CFC’s to catalyze breakdown of ozone.Polar Vortex • Similar, but less dramatic in Arctic.
Montreal Protocol of 1987• Identiﬁed CFC’s for elimination ﬁrst• Less harmful HCFC’s and HFC’s later• Bromine, Halons, Fumigants• Multinational Fund• Signiﬁcant repair of ozone layer: 2050
The Larger Questions...• Why was the Montreal Protocol so successful?• Why has the Kyoto Protocol been less successful?• Where is the line dividing economic prosperity and the environment?