Trends and characteristics of global CH4 emissions: Insights from UNFCCC greenhouse gas inventories

The trends and characteristics of global CH 4 emissions were analyzed using greenhouse gas data reported by both Annex I and non-Annex I countries under the United Nations Framework Convention on Climate Change (UNFCCC) from 1990 to 2021. The results show the following: (1) In 2021, the cumulative CH 4 emissions from the 42 nations listed in Annex I of the UNFCCC amounted to 1 871 521.79 kt CO 2 eq. The top 10 countries account for 82.0% of the total CH 4 emissions. (2) Most Annex I countries showed a gradual decline in CH 4 emissions over the period. In contrast, emissions from non-Annex I countries have increased year by year. Notably, CH 4 emissions in the United States, the European Union, the Russian Federation, and Ukraine decreased by 14.0%, 37.4%, 24.0%, and 60.9%, respectively. (3) In 2020, the CH 4 emissions of the agriculture, energy, waste treatment and LULUCF (land use, land-use change and forestry) sectors in Annex I countries were 72 240.43, 63 863.51, 41 573.08 and 88 9019 million tons of CO 2 eq, accounting for 38.6%, 34.1%, 22.2% and 4.8%, respectively. Among non-Annex I countries, the main CH 4 sources vary by country. In China and Mexico, energy and agriculture were the largest contributors, accounting for 44.8% and 40.2% in China, and 34.4% and 43.3% in Mexico, respectively. In India, Brazil, Nigeria, Argentina, and Vietnam, agriculture dominated, contributing 73.8%, 75.8%, 59.7%, 60.3%, and 58.5% of total emissions, respectively. Indonesia was an exception, with waste treatment being the primary source, accounting for 64.8% of its total CH 4 emissions. 基于《联合国气候变化框架公约》 (UNFCCC) 附件一国家提交的 1990 年至最新清单年份 (2021 年) 温室气体排放数据, 探讨了附件一和非附件一国家排放现状,演变趋势和关键排放源.结果表明:2021年UNFCCC附件一中42个国家CH 4 总排放量为1,871,521.79 kt CO 2 当量.排在前10位的国家占CH 4 总排放量的82.0%.(2)大多数附件一国家的CH 4 排放量呈逐渐下降趋势, 非附件一国家的CH 4 排放量呈逐年增加趋势, 其中最大的排放源的美国,欧盟(公约),俄罗斯联邦和乌克兰排放量分别下降了13.96%,37.44%,24.01%和60.89%.乌克兰,英国,意大利和罗马尼亚与1990年相比, 2021年的排放量减少了60%以上.(3) 2020年, 附件一国家农业,能源,废物处理和LULUCF行业的CH 4 排放量分别为72,240.43,63,863.51,41,573.08和889.19亿吨CO 2 当量, 占比分别为38.60%,34.11%,22.21%和4.75%.在UNFCCC非附件一国家中, 能源和农业部门是中国和墨西哥最主要的CH 4 排放源, 分别占中国总排放量的44.77%和40.23%, 占墨西哥总排放量的34.44%和43.29%.在印度,巴西,尼日利亚,阿根廷和越南, 农业部门是最主要的排放源, 分别占总排放量的73.75%,75.78%,59.66%,60.29%和58.47%.印度尼西亚以废物处理部门为主, 占总排放量的64.79%.