Atmosphere

• What are all of the layers of the atmosphere in order?

  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Exosphere
• What is the importance of ozone


  Prevents most high-energy UV from reaching Earth's surface, especially UVC and UVB. These can cause skin damage, cancer, DNA damage.
• Chlorofluorocarbons (CFC's)

  developed in 20s for conditioning, refrigeration and solvent cleaners.

  Rowland-Molina hypothesis: CFCs lead to O3 depletion because:

  • are chemically stable-- stay in atmosphere for long time to be carried to stratosphere.
  • react with O, preventing O3 formation.
• Evidence for ozone depletion


  Stratospheric air samples: by helium balloons & high-flying aircraft confirmed presence of ODSs.

  Ground based data: detection of higher UV levels in Antarctica.

  Measure O3 using Dobson Units to predict thickness of layer: 300 DU = normal. 220DU = "O3 hole"
• Ozone depletion over antarctica

  Stratospheric temperatures lower: allows clouds and ice crystals, surfaces where Chlorine molecules can be produced. "polar vortex" created by unique wind rotation maintains low temp, producing more Chlorine When spring arrives after completely dark winter, radicals cause O3 depletion.
• Restoration of the ozone layer

  The Montreal Protocol:

  Funds available for countries to follow.

  • Manufacture and use of CFC's phased out and banned
  • HCFC's phased out by 2030

  Use of alternative materials:

  • HCFC's to replace CFC's for refrigeration(less stable so don't reach stratosphere)
  • Hydrocarbons replaced CFC's as aerosol propellants (flammable -> fire risk)

  Safe disposal:

  CFC's from old fridges are drained and incinerated, broken down into CO2 and acidic gases which are neutralised with crushed lime
• Evaluation of effectiveness of control & ozone restoration

  It will be many years until total restoration, but severity of depletion is reducing.

  Causes of success of Montreal Protocol:

  • international recognition of consequences of O3 depletion.
  • agreements between nearly all countries.
  • development of alternatives, so most ODS use was unnecessary.
• Ecological consequences of climate change

  • changes to temperature and water availability affect species
  • distribution of species change, may colonise new areas. Human land use may block movement.
  • precipitation changes - wetland habitats expand/shrink
• Climatic consequences of climate change

  more heat retention changes atmospheric pressure and evaporation of water, producing new weather
• Wind pattern consequences of climate change


  Jet streams in Northern hemisphere are moving nearer to the pole, more slowly, creating waves that carry colder air southwards and warmer northwards. Slower movement causes longer, more intense weather.
• Rising sea levels consequences of climate change 


  occur for 2 reasons:

  • seawater expands under higher temperatures. However takes long time as there is much water in oceans and it has a high specific heat capacity.
  • melting land ice adds water to oceans, increasing sea level