Carbon dioxide and methane as greenhouse gases

• Greenhouse gases

  • Maintain temperatures on earth high enough to support life
  • Include: water vapour, carbon dioxide and methane
  • The greenhouse gas effect:
  • Electromagnetic radiation at most wavelengths from the sun passes through the Earth's atmosphere
  • The Earth absorbs some radiation and thus warms up. But some heat is radiated from the Earth as infrared radiation
  • Some of this IR radiation is absorbed by greenhouse gases in the atmosphere
  • Atmosphere warms up leading the the greenhouse effect and global warming
• Human activities which contribute to an increase in greenhouse gases in the atmosphere

  • Activities increase levels of carbon dioxide and methane
  • Examples of activities include : Driving, consuming electricity, raising livestock. decay of organic waste in landfill
  • Based on peer - reviewed evidence, many scientists believe that human activities will cause the temperature of the Earth's atmosphere to increase at the surface and that this will result in global climate change
• Human activities which contribute to an increase in greenhouse gases in the atmosphere


  • But, it is difficult to model such complex systems as global climate change.
  • This leads to simplified models, speculation and opinions presented in the media that may be based on only parts of the evidence and which may be biased.
• Global climate change

  • An increase in average global temperature is a major cause of climate change
  • There are several potential effects of global climate change, including:
  • Extinction of species
  • Raising sea levels due to the melting of polar ice caps
  • Migration- people will move from areas suffering drought/flooding
  • Decrease in crop yield for all major world crops
• Carbon footprint and its reduction

  ● Carbon footprint: the total amount of CO2 and other greenhouse gases emitted over the full life cycle of a product, service or event.

  ● It can be reduced by reducing emissions of carbon dioxide and methane e.g. by using less electricity (so using less fossil fuels or using an alternative source of electricity), by reducing the amount of travel or transportation (of either goods or people) and by planting more trees.
• Carbon footprint and its reduction 2

  ● However, action may be limited because it’s more difficult, can be more expensive and planting trees takes away land that could be used to grow crops.
• Atmospheric pollutants from fuels

  • Combustion of fuels is a major source of atmospheric pollutants
  • Most fuels ( including coal) contain carbon and/or hydrogen and may also contain some sulfur.
  • The gases released into the atmosphere when a fuel burns may include carbon dioxide, water (vapour), carbon monoxide, and oxides of nitrogen (which are formed at high temperatures). Solid particles and unburned hydrocarbons may also be released, forming particulates in the atmosphere
• Atomospheric pollutants from fuels 2

  • If there’s not enough oxygen, some of the fuel doesn’t burn – this is partial/incomplete combustion. Here, solid particles of soot (carbon), carbon monoxide and unburnt fuel are released.
  • The combustion of hydrocarbons releases energy. During combustion, the carbon and hydrogen in the fuels are oxidised to form carbon dioxide and water
• Properties and effects of atmospheric pollutants

  • Carbon monoxide: toxic gas which is colourless and odourless so not easy to detect
  • Sulfur dioxide and oxides of nitrogen: cause acid rain and respiratory problems in humans.
  • Particulates: cause global dimming and human health problems