CO₂ EQUIVALENT

The term "CO₂ equivalent" (or "CO₂e") is used to express the combined effect of all greenhouse gas (GHG) emissions in a single unit in order to be able to evaluate and compare the climate impact of different emissions.

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Besides carbon dioxide there are various types of gas which contribute to the greenhouse effect and have different effects on global warming depending on their heat absorbing capacity. These include:
 

• Methane gas (CH4) has a global warming potential about 25 times greater than carbon dioxide over a 100-year period;
   

• Nitrous oxide (N2O) has a global warming potential about 300 times that of carbon dioxide over a 100-year period.

 

Global Warming Potential (GWP) is used to measure (in CO₂e) the climate impact of each greenhouse gas, expressing how long it is capable of trapping heat in the atmosphere compared with carbon dioxide over a specific period of time (radiative forcing).

 

Let’s take for example methane (CH4) which has a GWP of about 25 over 100 years. This means that during this period, methane gas has a global warming potential 25 times that of CO₂ per unit of mass emitted. Thus, if we want to assess the overall climate impact of an activity that emits both methane and CO₂, we can convert the methane emissions into "CO₂ equivalent" by multiplying the amount of the methane emissions by its GWP.

 

The GWP of greenhouse gases are periodically published and updated by the IPCC.