Stratospheric Ozone
Ozone Layer Not really a layer: region of higher-than- normal ozone concentrations ~17 km-30 km altitude Absorbs ultraviolet (UV) radiation from sun, protecting organisms on surface from radiation damage
How Have We Depleted Ozone in the Stratosphere & What Can We Do? Noticed in 1980s Widespread use of certain chemicals has: Reduced ozone levels in the stratosphere Allowed more harmful ultraviolet radiation to reach the earth’s surface To reverse ozone depletion: Stop producing ozone-depleting chemicals Adhere to the international treaties that ban such chemicals
Information about Ozone Depletion Characterized as a rapid depletion of ozone over Antarctica during spring. Ozone hole season, Spring (August – October) Ozone hole located over mainly over Antarctica. Ozone hole recovers by late December Ozone hole not present in early 1970’s
Our Use of Certain Chemicals Threatens the Ozone Layer Ozone is thinning over Antarctica and the Arctic Chlorofluorocarbons (CFCs) Persistent chemicals that attack ozone in the stratosphere Mass-produced by industry, in refrigerants & consumer products like aerosol sprays Other chemicals: Hydrobromoflurocarbons (HBFCs), Methyl bromide, Hydrogen chloride, Carbon tetrachloride, methyl chloroform, n-propyl bromide, hexachlorobutadiene
Ozone equations Formation of ozone: O + O2 O3 Ozone depletion: CFCs split oxygen atoms to form (O2)
How do CFCs Break Down Ozone? CFCs and others released into troposphere CFCs move/drift upward into stratosphere UV radiation breaks apart CFCs releasing chlorine (bromine/fluorine) Sunlight causes chemical reaction allowing Cl to attack O3, creating O2
Montreal Protocol-An Environmental Success Story 1987, 36 initial nations Over 180 nations signed Montreal Protocol (including US) (during the Copenhagen Protocol: Amendment) Restricted CFC production globally Today: ozone holes are starting to recover Reasons for success: Government and industry cooperated on finding solutions Implemented with adaptive management: ability to fine-tune actions
Why Should We Worry About Ozone Depletion? Ozone protects the earth’s surface from damaging UV radiation Human health concerns UV radiation affects plankton (impairs/destroys) Disrupts food chains Damages fish/amphibians/mammals Widespread effects on major food crops Decrease plant productivity We can reverse it by: stop producing ozone-depleting chemicals immediately Agreements with a prevention approach: Montreal Protocol Cut emissions of CFCs Copenhagen Amendment Accelerated phase- out
The Chemicals Don’t Just Disappear… Worst ozone depletion: projected between 2010 and 2019.