Wetland emission and atmospheric sink changes explain methane growth in 2020

Article

关键词: MODEL DESCRIPTION;    CLIMATE-CHANGE;    SENSITIVITY;    SATELLITE;    ORCHIDEE;    TRENDS;    CH4;    CO2;   

DOI  :  10.1038/s41586-022-05447-w

来源: SCIE

【 摘 要 】

Atmospheric methane growth reached an exceptionally high rate of 15.1 +/- 0.4 parts per billion per year in 2020 despite a probable decrease in anthropogenic methane emissions during COVID-19 lockdowns(1). Here we quantify changes in methane sources and in its atmospheric sink in 2020 compared with 2019. We find that, globally, total anthropogenic emissions decreased by 1.2 +/- 0.1 teragrams of methane per year (Tg CH(4)yr(-1)), fire emissions decreased by 6.5 +/- 0.1 Tg CH(4)yr(-1) and wetland emissions increased by 6.0 +/- 2.3 Tg CH(4)yr(-1). Tropospheric OH concentration decreased by 1.6 +/- 0.2 per cent relative to 2019, mainly as a result of lower anthropogenic nitrogen oxide (NOx) emissions and associated lower free tropospheric ozone during pandemic lockdowns(2). From atmospheric inversions, we also infer that global net emissions increased by 6.9 +/- 2.1 Tg CH(4)yr(-1) in 2020 relative to 2019, and global methane removal from reaction with OH decreased by 7.5 +/- 0.8 Tg CH(4)yr(-1). Therefore, we attribute the methane growth rate anomaly in 2020 relative to 2019 to lower OH sink (53 +/- 10 per cent) and higher natural emissions (47 +/- 16 per cent), mostly from wetlands. In line with previous findings(3,4), our results imply that wetland methane emissions are sensitive to a warmer and wetter climate and could act as a positive feedback mechanism in the future. Our study also suggests that nitrogen oxide emission trends need to be taken into account when implementing the global anthropogenic methane emissions reduction pledge'.

【 授权许可】

Free