IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group I: The Physical Science Basis

Figure 2.7. Annual rates of change in the global atmospheric masses of each of the major LLGHGs expressed in common units of GtC yr–1. These rates are computed from their actual annual mass changes in Gt yr–1 (as derived from their observed global and annual average mole fractions presented in Figures 2.3 to 2.6 and discussed in Sections 2.3.1 to 2.3.4) by multiplying them by their GWPs for 100-year time horizons and then dividing by the ratio of the CO2 to carbon (C) masses (44/12). These rates are positive or negative whenever the mole fractions are increasing or decreasing, respectively. Use of these common units provides an approximate way to intercompare the fluxes of LLGHGs, using the same approach employed to intercompare the values of LLGHG emissions under the Kyoto Protocol (see, e.g., Prinn, 2004). Note that the negative indirect RF of CFCs and HCFCs due to stratospheric ozone depletion is not included. The oscillations in the CF4 curve may result partly from truncation in reported mole fractions.