The Earth's Atmosphere

• The atmosphere is a layer of gas surrounding the Earth.
• The early atmosphere was mostly composed of carbon dioxide.
• Oceans formed when water vapour condensed as the Earth cooled.
• Decrease in carbon dioxide to create today's atmosphere was caused by:

  • Dissolved in oceans
  • Photosynthesis
  • Converted into fossil fuels
  • Precipitated as insoluble metal carbonates
• About 2.7 billion years ago life started to appear and oxygen levels increased as it is a product of photosynthesis.
• The amount of nitrogen in the atmosphere has increased slowly as it is a very stable molecule.
• Scientists cannot be sure about the composition of the early atmosphere of the Earth as it was billions of years ago and evidence is limited.
• Current approximate composition of the atmosphere:

  80% Nitrogen

  20% Oxygen

  Small amounts of carbon dioxide, water vapour and noble gases
• A greenhouse gas is a gas that traps radiation from the sun.
• Greenhouse gases:

  • Carbon dioxide
  • Methane
  • Water vapour
• Greenhouse gases absorb longer wavelength infrared radiation.
• Burning fossil fuels and deforestation have increased atmospheric carbon dioxide.
• Rice farming and cattle farming have increased atmospheric methane.
• Global warming is an increase in the overall global average temperature.
• Global climate change is the change in long-term weather patterns across the planet.
• Some effects of climate change include:

  • Sea levels rising
  • Extreme weather events
  • Changes in the amount and time of rainfall
  • Changes to ecosystems and habitats
  • Polar ice caps melting
• A carbon footprint is the amount of carbon a product, process or person releases into the atmosphere over its lifetime.
• Carbon monoxide is formed by incomplete combustion and it is a colourless and odourless toxic gas.
• Particulates are formed by incomplete combustion that cause global dimming, respiratory problems and have a potential to cause cancer.
• Sulphur dioxide is formed by combustion of fossil fuels with sulphur impurities and it causes acid rain and respiratory problems.
• Nitrogen oxides are formed when atmospheric oxygen and nitrogen react in the heat of a combustion engine and it causes acid rain and respiratory problems.