Carbon dioxide equivalent (CO2e) is a measure of the total greenhouse effect of greenhouse gas emissions, expressed in terms of the greenhouse effect of carbon dioxide. Because each type of greenhouse gas (i.e., carbon dioxide, methane, nitrous_oxide and fluorinated gases) has a different greenhouse effect, converting their emissions into standard units makes it easier to compare the effects of emissions from different sources and to create optimal strategies for reducing them.
For example, methane is about 80 times more potent at causing global warming over a 20 year period than carbon dioxide, so each ton of methane emitted would be weighted the same as 80 tons of carbon dioxide, or 80 tons of carbon dioxide equivalent. Likewise for sulphur hexafluoride, the most destructive greenhouse gas, for which one ton equals about 23,000 tons of carbon dioxide or 23,000 carbon dioxide equivalent.