A comparative study of anthropogenic CH<sub>4</sub> emissions over China based on the ensembles of bottom-up inventories

Abstract

Abstract. Atmospheric methane (CH4) is a potent greenhouse gas that is strongly influenced by several human activities. China, as one of the major agricultural and energy production countries, contributes considerably to the global anthropogenic CH4 emissions by rice cultivation, ruminant feeding, and coal production. Understanding the characteristics of China's CH4 emissions is necessary for interpreting source contributions and for further climate change mitigation. However, the scarcity of data from some sources or years and spatially explicit information pose great challenges to completing an analysis of CH4 emissions. This study provides a comprehensive comparison of China's anthropogenic CH4 emissions by synthesizing the most current and publicly available datasets (13 inventories). The results show that anthropogenic CH4 emissions differ widely among inventories, with values ranging from 44.4–57.5 Tg CH4 yr−1 in 2010. The discrepancy primarily resulted from the energy sector (27.3 %–60.0 % of total emissions), followed by the agricultural (26.9 %–50.8 %) and waste treatment (8.1 %–21.2 %) sectors. Temporally, emissions among inventories stabilized in the 1990s but increased significantly thereafter, with annual average growth rates (AAGRs) of 2.6 %–4.0 % during 2000–2010 but slower AAGRs of 0.5 %–2.2 % during 2011–2015, and the emissions became relatively stable, with AAGRs of 0.3 %–0.8 %, during 2015–2019 because of the stable emissions from the energy sector (mainly coal production). Spatially, there are large differences in emissions hotspot identification among inventories, and incomplete information on emission patterns may mislead or bias mitigation efforts for CH4 emission reductions. The availability of detailed activity data for sectors or subsectors and the use of region-specific emission factors play important roles in understanding source contributions and reducing the uncertainty in bottom-up inventories. Data used in this article are available at https://doi.org/10.6084/m9.figshare.12720989 (Lin et al., 2021).

Methane emissions from China: a high-resolution inversion of TROPOMI satellite observations

“…7). This is because our inversion corrects livestock emissions upward in northwestern and northeastern China, where existing bottom-up inventories show weak emissions (Lin et al, 2021). Previous GOSAT inversions had poor observational coverage over these regions (Fig.…”

“…There are large uncertainties in these bottom-up estimates (Saunois et al, 2020;Gao et al, 2021). Different bottom-up national inventories for China as reported by Lin et al (2021) ranged from 44.4 to 57.5 Tg a −1 in 2010, with larger relative differences for individual sectors. These uncertainties make it difficult to set targets for reducing methane emissions.…”

“…It is crucial to quantify China's oil/gas and coal methane emissions in order to assess the climate benefits of switching from coal to gas (Alvarez et al, 2012(Alvarez et al, , 2018. Chinese oil/gas emissions in the most recent version of the widely used bottom-up EDGAR v6 inventory for 2018 (3.4 Tg a −1 ; Crippa et al, 2021) are much higher than in the government report to the UNFCCC (1.1 Tg a −1 ), while coal emissions in EDGAR v6 (20.4 Tg a −1 ) are consistent with the government report (19.5 Tg a −1 ). Previous versions of EDGAR overestimated coal emissions from China (Bergamaschi et al, 2013;.…”

An Integrated View of Homologous Emissions of Greenhouse Gases and Air Pollutants in China

“…Mt CH 4 yr-1 , respectively. This result probably occurs because of the higher estimates in EDGAR obtained based on higher emission factors for rice cultivation and coal mining[65,66]. N 2 O emissions continued to steadily increase, with an AAGR of 2.8% (before 2000) and the rate declined thereafter, with AAGRs of 2.3% and 1.9% in the 2000s and 2010-2015, respectively.…”

“…1.0%, respectively, and these rates increased notably during 2000-2009 (AAGRs: 9.4% and 3.1%, respectively) but thereafter gradually increased during 2010-2015 (AAGRs: 2.6% and 2.1%, respectively). Fossil fuel combustion, coal mining, and livestock are major drivers of the trends of CO 2 and CH 4 emissions in China[65][66][67]. Recent trends of emissions have stabilized or decreased mostly due to industrial structure updating, combustion e ciency improvement, and emissions control[67,68].…”