Greenhouse gases vary in their capacity to induce global warming.
Thus, the GWP for CH 4 is 21, which means that one tonne of CH 4 has the same warming effect as 21 tonnes of CO 2 . Using GWP to account for the contribution from all greenhouse gases, overall emissions can be reported as CO 2 equivalent emissions, i.e. total emissions of all gases expressed as an equivalent amount of CO 2 . Most of the activities included in the inventory produce greenhouse gases. However, some processes and activities, such as growth in vegetation, can result in the uptake of carbon from the biosphere, thereby acting as carbon sinks. To take this into account, both CO 2 emissions and CO 2 removals are included in the inventory so that net emissions can be calculated.