# Methane Emission Estimates by the Global High-Resolution Inverse Model Using National Inventories
## 4 Conclusions  
In this paper, we have presented a comparison of the methane bottom-up emission inventories with inversion estimates using the global 0.1\({}^{\circ}\)\(\times\) 0.1\({}^{\circ}\) high-resolution model NIES-TM-FLEXPART-VAR. The use of high-resolution transport helps to reduce biases in transport and inversion caused by the broadening of the anthropogenic emission plumes due to crude model resolution and numerical diffusion. EDGAR v4.3.2 provided methane emission values until 2012, and some differences in country totals can be found compared to the national reports to the UNFCCC, e.g., an underestimation of emissions by EDGAR in Russia by 50% and an overestimation by 20-40% for China and India. High resolution global inversion was employed to evaluate the effect of improved prior information using national reports with more detailed statistical data and country-specific emission factors. The original EDGAR v4.3.2 and the UNFCCC-adjusted emissions were used as two sets of anthropogenic prior emissions (for cases S0 and S1 respectively) together with biomass burning (GFASv1.2), wetlands (VISIT), and other natural sources. With the prior anthropogenic emissions adjusted from EDGAR to the UNFCCC, the total methane emissions optimized by inversion increased from 36.2 to 46 Tg CH\({}_{4}\) yr\({}^{-1}\) (27%) for Russia and 12.8 to 14.3 Tg CH\({}_{4}\) yr\({}^{-1}\) (12%) for temperate South America, and they decreased from 44.8 to 32.5 Tg CH\({}_{4}\) yr\({}^{-1}\) (28%) for India and 54 to 51.3 Tg CH\({}_{4}\) yr\({}^{-1}\) (5%) for China. The inverse corrections of total methane emissions also varied by region--upward by \(\sim\)18% (of the total) for tropical South America for both S0 and S1 cases, and downward by 22% and 15% for boreal North America, and 22% and 14% for China for both S0 and S1 cases, respectively. The most insignificant corrections occurred in central Eurasia and Japan (<2% for both cases). The ratios between the average flux (2010-2012) and the multi-annual average EDGAR and VISIT fluxes were also analyzed. Case S0 showed an apparent increase in anthropogenic emissions in central Europe, Russia,  
Figure 7: Observations, prior (forward), and posterior (optimized) modeled concentrations at selected sites in 2010. Mean bias and root-mean-square error (RMSE) values for each site are shown. (JF): 7.99E, 46.55N; MLO: 155.58W, 19.54N; PAL: 24.07E, 67.58N; and RYO: 144.32E, 39.03N). and contiguous USA, and a larger area of decrease in east China compared with case S1. The natural emissions shown for case S1 showed a greater increase in the Amazon area and decreases in Siberia and boreal North America compared to those shown for case S0. The inversions were also evaluated by the comparison between modeled concentrations and observations. The advantage of using the national reports to scale EDGAR emissions was supported by achieving a better fit for both the forward and optimized model simulations to the observations with our model setup. The country scale top-down emissions should be further evaluated and advanced to provide support for the improvement of the national reports to UNFCCC. Conceptualization, F.W. and S.M. ; methodology, S.M., F.W., A.T., and R.J.; software, S.M. ; formal analysis, F.W. ; investigation, F.W. and S.M. ; resources, T.M. ([PERSON]); data curation, A.T., A.I., M.S., T.M. ([PERSON]), E.J.D., I.M. ([PERSON]), Y.Y., J.W.K., I.M. ([PERSON]), J.V.L. and G.J.-M.; writing--original draft preparation, F.W. ; writing--review and editing, S.M., R.J., J.W.K., G.J.-M., and I.M. ([PERSON]); visualization, F.W. ; supervision, S.M. ; funding acquisition, T.M. ([PERSON]). This research was supported by GOSAT project (12288) at the National Institute for Environmental Studies, Japan. We thank the Ministry of the Environment, Japan for the financial support for the GOSAT project. The simulations were carried out using the Supercomputer System of the National Institute for Environmental Studies (NIES).