C13-Earth's atmosphere

• Composition of the atmosphere

  • 78% nitrogen
  • 21% oxygen
  • Small proportions of other gases including carbon dioxide, water vapour and noble gases
• Greenhouse layer


  Layer of gases including carbon dioxide, methane and water vapour that maintain the temperature on Earth high enough to support life
• Greenhouse layer


  Allows short wave infrared radiation from the Sun to pass through but absorbs the long wave infrared radiation emitted by the Earth, insulating the Earth
• Human activities that increase greenhouse gases

  • Combustion of fossil fuels
  • Deforestation
  • Methane release from farming
  • More animal farming (digestion, waste decomposition)
• Early atmosphere


  Mainly carbon dioxide, water vapour and small amounts of methane, ammonia and nitrogen, released by volcanoes. Little or no oxygen.
• Evolution of the atmosphere

  1. Water vapour condensed and formed oceans

  2. Carbon dioxide dissolved in oceans and formed carbonates

  3. Plants and algae evolved, decreasing carbon dioxide and increasing oxygen

  4. Sea animals used carbon dioxide to form shells and bones, which became limestone
• Combustion of fossil fuels has increased carbon dioxide and other harmful gases in the atmosphere
• Sulphur in fuels has increased sulphur dioxide, causing acid rain
• Carbon particles and carbon monoxide can be released from incomplete combustion
• Enhanced greenhouse effect


  Humans have added to the greenhouse layer through combustion of fossil fuels, increased farming and deforestation, leading to a rise in global temperature
• Potential effects of global climate change

  • Sea level rise, causing flooding and coastal erosion
  • More frequent and severe storms
  • Changes in amount, timing and distribution of rainfall
  • Water shortages for humans and wildlife
  • Changes in food producing capacity of some regions
  • Changes to distribution of wildlife species
• Water from houses and farming needs to be treated before release into rivers and lakes
• Water treatment process


  1. Filtering to remove large particles

  2. Sedimentation to remove sludge

  3. Anaerobic digestion of sludge to make methane gas

  4. Aerobic respiration to break down remaining effluent
• Carbon footprint


  Total amount of carbon dioxide and other greenhouse gases released over the life of a product
• Carbon neutral


  No net increase in carbon dioxide in the atmosphere
• Ways to reduce carbon footprint

  • Increased use of alternative energy supplies
  • Energy conservation
  • Carbon capture and storage
  • Carbon taxes and licences
  • Planting trees to offset carbon
• Potable water


  Water safe to drink, with low levels of dissolved salts and microbes
• Producing potable water in the UK

  1. Passing water through filter beds to remove solids

  2. Sterilising to kill microbes, using chlorine or UV light
• Desalination


  Process of removing salt from water, done by distillation or reverse osmosis, requires a large amount of energy