Global estimations of the inventory and mitigation potential of methane emissions from rice cultivation conducted using the 2006 Intergovernmental Panel on Climate Change Guidelines

TLDR

Global methane emissions from rice paddies are a key component of IPCC greenhouse‑gas inventories, yet previous estimates have not employed the 2006 IPCC guidelines. The study aimed to estimate global methane emissions from rice fields using the Tier 1 method of the 2006 IPCC guidelines. The authors applied the Tier 1 method with country‑specific rice harvest area statistics and expert estimates of agricultural activities. The 2000 estimate was 25.6 Tg yr⁻¹ (95 % CI 14.8–41.7 Tg yr⁻¹), and the analysis showed that draining continuously flooded fields or applying off‑season rice straw could each cut emissions by 4.1 Tg yr⁻¹, with both measures together reducing emissions by 7.6 Tg yr⁻¹, while any accompanying nitrous‑oxide rise would have a negligible global‑warming‑potential impact.

Abstract

The Intergovernmental Panel on Climate Change (IPCC) regularly publishes guidelines for national greenhouse gas inventories and methane emission (CH 4 ) from rice paddies has been an important component of these guidelines. While there have been many estimates of global CH 4 emissions from rice fields, none of them have been obtained using the IPCC guidelines. Therefore, we used the Tier 1 method described in the 2006 IPCC guidelines to estimate the global CH 4 emissions from rice fields. To accomplish this, we used country‐specific statistical data regarding rice harvest areas and expert estimates of relevant agricultural activities. The estimated global emission for 2000 was 25.6 Tg a −1 , which is at the lower end of earlier estimates and close to the total emission summarized by individual national communications. Monte Carlo simulation revealed a 95% uncertainty range of 14.8–41.7 Tg a −1 ; however, the estimation uncertainty was found to depend on the reliability of the information available regarding the amount of organic amendments and the area of rice fields that were under continuous flooding. We estimated that if all of the continuously flooded rice fields were drained at least once during the growing season, the CH 4 emissions would be reduced by 4.1 Tg a −1 . Furthermore, we estimated that applying rice straw off season wherever and whenever possible would result in a further reduction in emissions of 4.1 Tg a −1 globally. Finally, if both of these mitigation options were adopted, the global CH 4 emission from rice paddies could be reduced by 7.6 Tg a −1 . Although draining continuously flooded rice fields may lead to an increase in nitrous oxide (N 2 O) emission, the global warming potential resulting from this increase is negligible when compared to the reduction in global warming potential that would result from the CH 4 reduction associated with draining the fields.