Atmosphere

Atmosphere

1. Composition

   • Changes with time - photosynthesis, respiration rates, geoglogial/human activities, water vapour conc.
   • Changes with altitude - ozone in stratosphere, temp declines with increasing altitude in troposphere (IR heatingfrom ground), increases with altitude in stratosphere (UV heating), atmospheric pressure decreases with increasing altitude.
   • Solar radiation - nuclear fusion releasing electromagnetic radiation, UV absorbed by ozone, water vapour/carbon dioxide absorb visible and IR, some reflected by clouds/particulate matter.

2. Human impacts and consequences

   • Global climate change - greenhouse effect/enhanced.
   • Consequences - sea level rise (thermal expansion, melting land ice), wind and precipitation patterns, ocean current (El Nino, La Nina), North Atlantic conveyor, ecological changes.
   • Predictions - small changes over long periods, different locations, limited/unreliable historical data, partly natural, not fully understood.

3. Feedback mechanisms

   • Positive - environmental change, causes other change, increase original.
     • Warming increase decomposition, more carbon dioxide, more warming. Warming reduces ice, reduces albedo, less reflection, heating increased.
   • Negative - environmental change, causes other change, decrease original.
     • Higher temps, increased photosynthesis, more carbon in biomass, carbon dioxide decreased, lower temps. Warming increases evaporation, low-level cloud, increased albedo, reduced heating.

4. Coping with climate change

   • Kyoto protocol - MEDC's reduce emissions by 5.2% below their 1990 levels. Failure leads to permitted emissions reduced by 30%. Country developed own method. LEDC's not legally bound, hinder development.
   • Agriculture - cultivate warmer climate/drought-resistant crops, abandon areas with unsustainable irrigation, water storage in surplus.
   • Carbon dioxide - energy conservation, renewable, carbon sequestation (afforestation), kyoto protocol.
   • Methane - reduced dumping waste in landfill, reduced livestock production, gas collection.
   • Oxides of N/tropospheric ozone - reduced internal combustion, catalytic converters (car exhausts), addition of urea to power station effluents/diesel engine exhausts.
   • CFC's - alternative materials (HFCs, butane/propane aerosols, alcohol solvents, trigger/pump spray cleaners, stick deodorants.)
   • Building design - better ventilation/cooling systems/paler colours reducing need for air con, stronger buildings (storm damage.)
   • Flooding - riverbank defences/barrages, less flood plain building, reduced runoff rates (reduced tarmac), river regulation dams.
   • Coastal erosion - improved coastal defences, managed retreat (abandon lower value areas difficult to defend.)

5. Ozone depletion

   • Concern - UVB not absorbed, reach surface, absorbed by living cells, damaging them.
   • UVA not absorbed by ozone, UVB almost fully absorbed by ozone, UVC completely absorbed by ozone.
   • Caused by chlorine, single Cl atom (chlorine radical, single electron) is very reactive, reacts with ozone molecule, breaking it down, leaves oxygen molecule and chlorine monoxide. Cl monoxide reacts with monatomic oxygen, makes chlorine dioxide, breaks down releasing Cl again repeating reactions.
   • CFCs - refridgerants, aerosol propellants, solvents, expanded gases for plastics. Chemically stable, low solubility, stay in atmosphere. Broken down by UV in stratosphere, produce Cl which causes depletion.
   • Montreal Protocol - phased out manufacture/use of CFC's and ozone-depleting substances, replaced by HCFCs (for refrigerators, contain Cl but less chemically stable) and alcohols, trigger pack sprays,
   • Polar regions - greater depletion, reactions occur easily at low temps due to ice crystals acting as catalytic surfaces.
   • Other gases - oxides of nitrogen are possible causes, released in troposphere not reaching stratosphere as they dissolve in rain or react. Released by high flying aircraft.

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