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					Bay Area Earth Science Institute (BAESI)



      Ozone depletion:
       Misconceptions

          San Jose State University,
                January 24, 2004
        http://www.met.sjsu.edu/baesi/




                Weather and Climate        1
How is ozone produced?

 Ozone is produced and destroyed naturally
 Production:
  – It is formed when oxygen absorbs solar radiation
           O2 +UV radiation  O+O
                     O+ O2  O3
 Ozone reacts with various other chemicals, and thus
  is highly reactive (i.e.)  O + Cl ClO + O
                                      3               2
                                   ClO + O Cl + O2
 Net : O3 +O 2O2
 One Cl atom can destroy ~100,000 ozone molecules
                    Weather and Climate                   2
                 Ozone, the good and the bad
Ozone is often
confused:
                                                  Stratosphere
Good ozone:
 Stratospheric ozone
                   Altitude (km)
 The ozone layer

Bad ozone:
 Tropospheric ozone
 Smog                                              Troposphere




                                   ozone amount
UV radiation

What affects the amount of UV radiation hitting the Earth?

    Location (latitude)
 _______________________
    Time of year
 _______________________
    Time of day
 _______________________
      Cloud
   _______________________
      amount
      Ozone
   _______________________
      amount


                        Weather and Climate                  7
Concept Map




              Weather and Climate   10
                 Concept Map Terms


 Ozone
 UV radiation
                                           Dobson Unit
 Sun
                                           Total Ozone
 Gas
                                           Tropospheric ozone
 Skin Cancer
                                           Good ozone
 Summer
                                           Stratospheric ozone
 Winter
                                           Bad ozone
 Spring
                                      
 Atmosphere
 CFC’s
 South Pole
 Trends
 Ozone hole
 Chlorine

                      Weather and Climate                         11
History of Ozone Depletion
 Chlorofluorocarbons (CFCs) developed in 1940’s
  and 50’s as:
   – Refrigerants, propellants, fire retardants
 1970’s CFCs detected in upper atmosphere.
   – Many of these have long atmospheric lifetimes:
      –(10’s to 100’s of years)
  – 1974 Rowland and Molina propose that CFC’s
    can destroy ozone in the stratosphere.
  – CFC contain chlorine (Cl)
  – Chlorine can destroy ozone rapidly
                    Weather and Climate               12
 What causes the ozone hole?
 Ozone Hole Recipe (make your own!)
        Abundant chlorine
  – 1. _____________________
  – 2. _____________________
        Cold temperatures
      Formation of Polar Stratospheric Clouds (PSC’s)
  – 3. ______________________
        Sunlight to activate chemistry


 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.
                       Weather and Climate                15
Is the ozone hole getting much
            bigger?

                                  No, not over
                                  the last few
                                  years




            Weather and Climate                  17
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.

                     Weather and Climate               18
Is the Montreal Protocol working?

Seems to be…

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




                     Weather and Climate        19
Weather and Climate   20
What is the connection between ozone
depletion and global warming?

 No direct connection between these environmental
  issues.
 However: Global warming may enhance
ozone depletion
 Global warming produces:

  – Tropospheric warming & stratospheric cooling
  – Therefore, if the stratosphere cools, then ozone
    destroying chemistry (e.g. ozone hole), will
    increase.
                    Weather and Climate                21
 What are predictions for the future?

 Model simulations suggest:
  – atmospheric chlorine will return to pre-80’s level
     In next 50 years or so
    __________________ .
A slow ozone recovery should follow
decreasing chlorine concentrations!!!
  – Uncertainties still remain:
      ____________________
        Phase out of CFC’s
      ____________________
         Influence of global warming


                     Weather and Climate                 22
                 Concept Map Terms


 Ozone
 UV radiation
 Sun                                  Dobson Unit
 Gas                                  Total Ozone
 Skin Cancer                          Tropospheric ozone
 Summer                               Good ozone
 Winter                               Stratospheric ozone
 Spring                               Bad ozone
 Atmosphere                           Recovery
 CFC’s
 South Pole                           TOMS
 Trends                               Gas
 Ozone hole                           2050
 Chlorine                             Cold temperatures
                                       Northern Hemisphere


                      Weather and Climate                     23
   Spring
                                                                              Sun
                                                                                                                Skin
                                                                                                               Cancer

                                                                                     produces
                           Atmosphere
 present in                                     is a                                                       causes
                                                                 Gas
                                                                                                UV
         Ozone                                                                              Radiation
         Hole
                                                                                                              Automobiles
                                    is present in the
                                                              is a
              is depletion of                                             protects the
                                                                          earth from                     produce
cause
                            Good                          Ozone                             Bad
                            Ozone                                                          Ozone
 CFC’s                                                                                                  may cause

                                                                                                                     Global
                                         has                                                    has                 Warming
                      destroy
   contain
                                               Stratosphere
                                                                                                Troposphere
               Chlorine
                                                                     is the column


                                Dobson
                                 Unit                                       Total
                                               is measurement of            Ozone
Misconceptions

 Ozone depletion and global warming often
  confused
   – Ozone depletion – CFC’s (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
  –…
                    Weather and Climate                 25

				
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