The role of rice cultivation in changes in atmospheric methane concentration and the Global Methane Pledge.

Resumption of the increase in atmospheric methane (CH 4 ) concentrations since 2007 is of global concern and may partly have resulted from emissions from rice cultivation. Estimates of CH 4 emissions from rice fields and abatement potential are essential to assess the contribution of improved rice management in achieving the targets of the Global Methane Pledge agreed upon by over 100 countries at COP26. However, the contribution of CH 4 emissions from rice fields to the resumed CH 4 growth and the global abatement potential remains unclear. In this study, we estimated the global CH 4 emissions from rice fields to be 27 ± 6 Tg CH 4 year -1 in the recent decade (2008-2017) based on the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories. The trend of CH 4 emissions from rice cultivation showed an increase followed by no significant change and then, a stabilization over 1990-2020. Consequently, the contribution of CH 4 emissions from rice fields to the renewed increase in atmospheric CH 4 concentrations since 2007 was minor. We summarized the existing low-cost measures and showed that improved water and straw management could reduce one-third of global CH 4 emissions from rice fields. Straw returned as biochar could reduce CH 4 emissions by 12 Tg CH 4 year -1 , equivalent to 10% of the total reduction of all anthropogenic emissions. We conclude that other sectors than rice cultivation must have contributed to the renewed increase in atmospheric CH 4 concentrations, and that optimizing multiple mitigation measures in rice fields could contribute significantly to the abatement goal outlined in the Global Methane Pledge.