A recent analysis of satellite data has revealed that the remarkable surge in atmospheric methane emissions observed from 2020 to 2022 was driven primarily by increased inundation and water storage in wetlands, coupled with a slight decrease in atmospheric hydroxide (OH). This surge, compared to the trend seen from 2010 to 2019, has important implications for efforts to reduce atmospheric methane levels and mitigate its impact on climate change. The findings indicate a shift from the regular increases in methane concentrations seen in the previous decade to a significant surge in emissions during the pandemic shutdown period.
Global methane emissions increased from approximately 499 teragrams (Tg) to 550 Tg between 2010 and 2019, followed by a surge to 570 – 590 Tg between 2020 and 2022. While one of the leading theories behind the sudden increase in methane emissions was the decrease in human-made air pollution during the pandemic shutdown, the researchers found that this decrease in OH levels only accounted for 28% of the surge. Instead, the majority of the increase was attributed to inundation events in equatorial Asia and Africa, which accounted for 43% and 30% of the additional atmospheric methane, respectively.
The heavy precipitation in these wetland and rice cultivation regions, likely associated with La Niña conditions from 2020 to early 2023, led to an increase in anaerobic microbial activity in wetlands. The microbes in wetlands produce methane as they metabolize and break down organic matter in the absence of oxygen. Increased water storage in wetlands results in more anaerobic microbial activity and higher methane emissions to the atmosphere. This highlights the importance of understanding and monitoring wetland emissions to develop effective mitigation strategies for methane.
The researchers emphasize the importance of studying wetland emissions and how methane production responds to changes in precipitation patterns in tropical wetland ecosystems. Improved observations of wetland methane emissions are crucial for understanding the role of precipitation patterns in driving methane concentrations in the atmosphere. This research provides valuable insights into the factors contributing to the increased methane concentrations observed since 2010, with wetlands identified as a key driver of methane emissions.
The research, published in the Proceedings of the National Academy of Sciences, was supported in part by the NASA Early Career Investigator Program. Lead author Zhen Qu conducted the research while a postdoctoral researcher at Harvard University, with contributions from researchers at institutions such as the California Institute of Technology’s Jet Propulsion Laboratory and the University of Leicester. The study highlights the complex interactions between wetland emissions, precipitation patterns, and atmospheric chemistry in driving global methane emissions. Understanding these mechanisms is crucial for developing effective strategies to mitigate methane emissions and combat climate change.
