CO2e is the shorthand for carbon dioxide equivalents. It is the standard unit in carbon accounting to quantify greenhouse gas emissions, emissions reductions and carbon credits

It is expressed in tonnes and written as tCO2e, although properly the ‘2’ should be a subscript. Sometimes a hyphen is included, tCO2-e

One tonne of carbon dioxide has become the standard unit for greenhouse gases and emissions of gases other than carbon dioxide are converted according to their global warming potential.

Greenhouse gases that have the greatest influence on atmospheric warming include

  • Carbon dioxide
  • Methane
  • Nitrous oxide
  • Water vapour
  • Tropospheric ozone
  • Chlorofluorocarbons (CFCs)
  • Hydrochlorofluorocarbons (HCFCs)
  • Perfluorocarbons
  • Sulphur hexafluoride

Each has a different contribution to the greenhouse effect with some have a greater global warming potential than others.

  • 1x Carbon dioxide
  • 12x Methane
  • 114x Nitrous oxide
  • 270x Hydrochlorofluorocarbons (HCFCs)
  • 3200x Sulphur hexafluoride

To keep accounting equivalent each tonne of greenhouse gas is divided by its global warming potential and expressed in tCO2e

CO2e was an important breakthrough in finding climate change policy andsolutions for global warming because it provides a standard unit that can be measured and is agreed to by all stakeholders.

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