# Methane Emission Estimates by the Global High-Resolution Inverse Model Using National Inventories
## 3 Results and Discussion
### Estimation of Global Methane Emissions  
The analysis in this study was based on bi-weekly emissions estimated for the years 2010-2012 using the inverse modeling system with variational optimization to two categories of fluxes: anthropogenic and natural (wetlands). Monthly emissions were calculated and analyzed for two sets of simulations: S0 simulation with EDGAR v4.3.2 and S1 simulation with EDGAR scaled to UNFCCC reports.  
The global total anthropogenic emissions estimated by EDGAR were 347 Tg CH\({}_{4}\) yr\({}^{-1}\) (average 2010-2012) while EDGAR adjusted to UNFCCC reports gave 338 Tg CH\({}_{4}\) yr\({}^{-1}\) (98% of EDGAR). The global total natural emissions from wetlands and biomass burning were 204 Tg CH\({}_{4}\) yr\({}^{-1}\). The global total prior methane emissions were 557 Tg CH\({}_{4}\) yr\({}^{-1}\) for S0 and 548 Tg CH\({}_{4}\) yr\({}^{-1}\) for S1. The optimized global anthropogenic emissions were 350 Tg CH\({}_{4}\) yr\({}^{-1}\) and 344 Tg CH\({}_{4}\) yr\({}^{-1}\) for S0 and S1, respectively. The optimized global total methane emissions were 572 Tg CH\({}_{4}\) yr\({}^{-1}\) and 566 Tg CH\({}_{4}\) yr\({}^{-1}\) for S0 and S1, respectively. The differences between the total methane emissions reduced from the prior  
Figure 1: Comparison of anthropogenic methane emissions (units: Tg CH\({}_{4}\) yr\({}^{-1}\)) between national reports to the UNFCCC and EDGAR v4.3.2 (G1: group 1, G2: group 2, and G3: group 3). The top emitting countries (based on the amount of emissions in the year 2012) are presented.  
values after inversion. Those results are slightly higher than the previous estimation of \(548^{+21}_{-22}\) Tg CH\({}_{4}\) yr\({}^{-1}\) reported by [PERSON] et al. (2014) and the Intergovernmental Panel on Climate Change (IPCC) ([PERSON] et al., 2016).  
Figure 2 shows the average monthly global total and anthropogenic prior and estimated emissions. The inverse model produced lower emissions in winter compared with prior emissions and enhanced emissions in summer. Case S0 showed a more pronounced summer peak compared to case S1. The summer maximum appeared in July-August with its larger share of emissions from natural sources (e.g., wetlands, biomass burning, and lakes) and the agriculture sector ([PERSON] et al., 2016) when minimum CH\({}_{4}\) concentrations were recorded in most places of the northern hemisphere due to the larger CH\({}_{4}\) sink as a result of the strong chemical reaction with OH in the warm season ([PERSON] et al., 2016). Significant differences were found between the prior and posterior fluxes in winter and summer. Since seasonal cycle separation depends on latitude and the average time period, Figure 2a shows the average for three entire years and the whole region for both prior and posterior fluxes. Figure 2b shows the monthly variation of wetland emissions and anthropogenic emissions in selected regions including boreal America, the contiguous USA, Europe, Russia, and China in the northern hemisphere, where the wetland emissions were low in winter and the difference between prior and posterior anthropogenic emissions was more independent from wetland emission uncertainties.