Carbon dioxide equivalent

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Carbon dioxide equivalent or CO₂e, is an internationally accepted measure that encapsulates all GHGs (greenhouse gases) that contribute to global warming (e.g. methane, perfluorocarbons, nitrous oxide, etc). As the mainstream media grasps "carbon" and "CO₂" jargon, it should be noted that CO₂e is a more correct/broad measure of total GHG contribution.

The CO₂e of an amount used to compare the emissions from various greenhouse gases based upon the amount of carbon dioxide that would have the same global warming potential (GWP), measured over a specified timescale (generally, 100 years) for emissions or current GWP for existing GHG concentrations.

Carbon dioxide equivalents (CDE) are commonly expressed:

• In industry as million metric tonnes of carbon dioxide equivalents (MMTCDE).
• In vehicles as g of carbon dioxide equivalents / km (gCDE/km).

The carbon dioxide equivalent for a gas is derived by multiplying the mass of the gas by the associated GWP.

MMTCDE = (million metric tonnes of a gas) * (GWP of the gas).
gCDE = (grams of gas) * (GWP of the gas).

For example, the GWP for methane is 21 and for nitrous oxide 310. This means that emissions of 1million metric tonnes of methane and nitrous oxide respectively is equivalent to emissions of 21 and 310 million metric tonnes of carbon dioxide.

[edit] See also

• Emission standard.
• Fuel efficiency
• IPCC Third Assessment Report, 2001 .
• Kyoto Protocol.

[edit] References