Greenhouse Gases


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•  Carbon dioxide and water vapour are the most significant greenhouse gases

•  Other gases including methane and nitrogen oxides have less impact

Greenhouse gases absorb and emit long-wave (infrared) radiation, thereby trapping and holding heat within the atmosphere

  • Greenhouse gases collectively make up less than 1% of the Earth’s atmosphere

The greenhouse gases which have the largest warming effect within the atmosphere are water vapour (clouds) and carbon dioxide

  • Water vapour is created via evaporation of water bodies (e.g. oceans) and transpiration – it is removed via precipitation (rain)
  • Carbon dioxide is made by cell respiration and burning fossil fuels – it is removed via photosynthesis and absorption by oceans

Other greenhouse gases include methane and nitrogen oxides – these have less impact on the overall warming effect

  • Methane is emitted from waterlogged habitats (like marshes) and landfills – it is also a gaseous waste produced by ruminants
  • Nitrogen oxides are released naturally by certain bacteria and also is emitted in the exhaust by certain vehicles

Water vapour is the most abundant greenhouse gas in the atmosphere, but is not produced as a product of human activity

Proportion of Greenhouse Gases (Natural vs Anthropomorphic)

greenhouse gas chart

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•  The impact of a gas depends on its ability to absorb long-wave radiation as well as its concentration within

    the atmosphere

There are two factors which determine how much of an the impact a greenhouse gas will have in warming the atmosphere:

1.  Ability to absorb long-wave radiation

  • Gases that have a greater capacity to absorb long-wave radiation will have a greater warming impact (per molecule)

2.  Concentration within the atmosphere

  • The greater the concentration of a gas, the greater its warming impact will be within the atmosphere
  • The concentration of a gas will be determined by both its rate of release and persistence within the atmosphere

The overall impact of a greenhouse gas will be determined by the combination of both these factors

  • Methane has a larger capacity to absorb long-wave radiation than carbon dioxide, but is significantly less abundant
  • Water vapour enters the atmosphere rapidly but only remains for short periods, while carbon dioxide persists for years
  • Human activity is increasing the amount of greenhouse gases (except water vapour) and hence increasing their impact

Summary of Greenhouse Gas Impacts

greenhouse gases