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Global warming potential
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<p>Global warming potential (GWP) is a measure of how much heat a <a href="/facts/Greenhouse_gas/HXaHqrT8">greenhouse gas</a> traps in the atmosphere over a specific time period, relative to <a href="/facts/Carbon_dioxide/xGzpppEp">carbon dioxide</a> (CO2).: 2232 It is expressed as a multiple of warming caused by the same <a href="/facts/Mass/HHdc8XmF">mass</a> of <a href="/facts/Carbon_dioxide/xGzpppEp">carbon dioxide</a> (CO2). Therefore, by definition CO2 has a GWP of 1. For other <a href="/facts/Gas/hVVAoodV">gases</a> it depends on how strongly the gas absorbs thermal radiation, how quickly the gas leaves the atmosphere, and the time frame considered. </p><p>For example, <a href="/facts/Methane_emissions/IrclnYfB">methane</a> has a GWP over 20 years (GWP-20) of 81.2 meaning that, a <a href="/facts/Fugitive_gas_emissions/cFjpMyk5">leak</a> of a tonne of methane is equivalent to emitting 81.2 tonnes of carbon dioxide measured over 20 years. As methane has a much shorter atmospheric lifetime than carbon dioxide, its GWP is much less over longer time periods, with a GWP-100 of 27.9 and a GWP-500 of 7.95.: 7SM-24 </p><p>The carbon dioxide equivalent (CO2e or CO2eq or CO2-e or CO2-eq) can be calculated from the GWP. For any gas, it is the mass of CO2 that would warm the earth as much as the mass of that gas. Thus it provides a common scale for measuring the <a href="/facts/Effects_of_climate_change/M5EvHf14">climate effects</a> of different gases. It is calculated as GWP times mass of the other gas. </p>