1 Ozone depletion: Misconceptions Misconceptions Meteorology 10 De Anza College

2 How is ozone produced? Ozone is produced and destroyed naturally Production: It is formed when oxygen absorbs solar radiation Ozone reacts with various other chemicals, and thus is highly reactive (i.e.) Net : O 3 +O  2O 2 One Cl atom can destroy ~100,000 ozone molecules

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4 Ozone, the good and the bad ozone amount Altitude (km) Ozone is often confused: Good ozone: Bad ozone: Stratosphere Troposphere

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6 UV radiation What affects the amount of UV radiation hitting the Earth?   _______________________

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9 History of Ozone Depletion Chlorofluorocarbons (CFCs) developed in 1940’s and 50’s as: 1970’s CFCs detected in upper atmosphere. Many of these have long atmospheric lifetimes: 1974 Rowland and Molina propose that CFC’s can destroy ozone in the stratosphere. CFC contain chlorine (Cl)

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11 What causes the ozone hole? Ozone Hole Recipe (make your own!) 1._____________________ 2._____________________ Formation of Polar Stratospheric Clouds (PSC’s) Formation of Polar Stratospheric Clouds (PSC’s) 3. ______________________ Winter Polar Vortex is region of strong winds forming an isolated ‘container’ from the middle latitudes. This produces cold temperatures. Allows chemistry to develop undisturbed.

12 Is the ozone hole getting much bigger?

13 What is being done about ozone depletion? Montreal Protocol ~ (1988) international agreement to phase out ozone depleting chemicals Further amendments accelerated the phase out. Developed countries have switched to HCFC’s (more ozone friendly!) Developing countries have until 2004 to phase out CFC’s.

14 Is the Montreal Protocol working? Seems to be… Recent observations indicate that chlorine is beginning to decline in the atmosphere.

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16 What is the connection between ozone depletion and global warming? No direct connection between these environmental issues. No direct connection between these environmental issues. Global warming produces: Global warming produces: Tropospheric warming & stratospheric cooling Tropospheric warming & stratospheric cooling Therefore, if the stratosphere cools, then ozone destroying chemistry (e.g. ozone hole), will increase. Therefore, if the stratosphere cools, then ozone destroying chemistry (e.g. ozone hole), will increase.

17 Model simulations suggest: Model simulations suggest: atmospheric chlorine will return to pre-80’s level atmospheric chlorine will return to pre-80’s level __________________. __________________. Uncertainties still remain: Uncertainties still remain: ____________________ ____________________ What are predictions for the future?

18 Misconceptions Ozone depletion and global warming often confused Ozone depletion and global warming often confused Ozone depletion – CFC’s (aerosols, refrigerants) Ozone depletion – CFC’s (aerosols, refrigerants) Global Warming – burning of fossil fuels Global Warming – burning of fossil fuels Some student ideas Some student ideas Hole in ozone hole allows more heat into atmosphere Hole in ozone hole allows more heat into atmosphere Automobile exhaust responsible for ozone depletion Automobile exhaust responsible for ozone depletion …