Ozone depletion:

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Meteorology 10De Anza College

• Ozone depletion
• Misconceptions

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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 O3 O? 2O2 One Cl atom
can destroy 100,000 ozone molecules
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Ozone, the good and the bad
Ozone is often confused Good ozone Bad
ozone
Stratosphere
Altitude (km)
Troposphere
ozone amount
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UV radiation

• What affects the amount of UV radiation hitting
  the Earth?
• _______________________
• _______________________
• _______________________
• _______________________
• _______________________

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

• Ozone Hole Recipe (make your own!)
• _____________________
• _____________________
• Formation of Polar Stratospheric Clouds (PSCs)
• 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.

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Is the ozone hole getting much bigger?
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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
HCFCs (more ozone friendly!) Developing
countries have until 2004 to phase out CFCs.
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Is the Montreal Protocol working?

• Seems to be
• Recent observations indicate that chlorine is
  beginning to decline in the atmosphere.

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What is the connection between ozone depletion
and global warming?

• No direct connection between these environmental
  issues.
• Global warming produces
• Tropospheric warming stratospheric cooling
• Therefore, if the stratosphere cools, then ozone
  destroying chemistry (e.g. ozone hole), will
  increase.

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What are predictions for the future?

• Model simulations suggest
• atmospheric chlorine will return to pre-80s
  level
• __________________ .
• Uncertainties still remain
• ____________________
• ____________________

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Misconceptions

• Ozone depletion and global warming often confused
• Ozone depletion CFCs (aerosols, refrigerants)
• Global Warming burning of fossil fuels
• Some student ideas
• Hole in ozone hole allows more heat into
  atmosphere
• Automobile exhaust responsible for ozone
  depletion