GHG INVENTORY The emission quantities of the six recognized GHGs were then converted to metric tons of CO 2 equivalent (CO 2 e) using global warming potential (GWP) to normalize the GHGs.2 GWP is the ratio of radiative forcing to the degree of atmospheric warming that would result from the emission of one mass-based unit of a given GHG compared to one equivalent unit of CO 2 over a period of time.