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What are Greenhouse Gas Emissions?

earth question markGreenhouse gases (GHGs) trap the heat that is reflected from the earth’s surface, resulting in a rise in air and surface temperatures. This is similar to the way in which sunlight shines in through a greenhouse's glass windows, is converted to heat, and is then trapped inside creating a warm growing environment for plants (hence the expression "Greenhouse Gas Effect").

This is fine for a small plant greenhouse, but for our planet as a whole, it can be catastrophic if overall temperature is allowed to rise too much. The IPCC estimates that we can only allow our planet to warm a total of 2°C from pre-industrial days before we experience detrimental effects – we have already allowed it to rise 1ºC and is still climbing.

Major contributors of GHGs in our atmosphere are oil-based forms of transportation (cars, trucks, trains, buses, planes, boats, ships, heavy machinery), electrical power plants burning coal or natural gas, other industry burning coal, livestock production, natural releases of gases from the earth (thawing permafrost, oceans, volcanoes, decomposing vegetation, fires).

There are various greenhouse gases – some more potent than others.

The GHG data reported by IPCC contain estimates for direct greenhouse gases, such as:

  • CO2 - carbon dioxide
  • CH4 - methane
  • N2O - nitrous oxide
  • PFCs - perfluorocarbons
  • HFCs - hydrofluorocarbons
  • SF6 - sulphur hexafluoride well as for the indirect greenhouse gases such as SO2, NOx, CO and NMVOC.

CO2 equivalents

The term equivalent CO2 is used for simplicity. Each greenhouse gas has a different global warming potential (GWP) and persists for a different length of time in the atmosphere.

The three main greenhouse gases (along with water vapour) and their 100-year global warming potential compared to carbon dioxide are: (1)

  • Carbon dioxide (CO2):  1 x
  • Methane (CH4):  25 x more powerful
  • Nitrous oxide (N2O):  298 x more powerful

Water vapour is not considered to be a cause of man-made global warming because it does not persist in the atmosphere for more than a few days.

There are other greenhouse gases which have far greater global warming potential (GWP) but are much less prevalent. These are sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs).

There are a wide variety of uses for SF6, HFCs, and PFCs but they have been most commonly used as refrigerants and for fire suppression. Many of these compounds also have a depleting effect on ozone in the upper atmosphere.


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