New Study Uncovers Slower Methane Emission Reduction In Los Angeles, Challenging Previous Estimates

Washington, DC /PRNewswire/ - A team of scientists recently conducted a comprehensive analysis using atmospheric remote sensing measurements and a data product developed by Dr. Tomohiro Oda of Universities Space Research Association. This study, led by researchers at California Institute of Technology and NASA's Jet Propulsion Laboratory and co-authored by Dr. Oda, has unveiled critical insights into methane (CH₄) emissions. The findings indicate that the previously reported reduction rate of CH₄ in the Los Angeles area was overestimated. The study outlines the urgency for accelerated reduction efforts to meet the pledge goal for 2030. The results were published in Nature Communications.

The research indicated that Methane (CH₄) emissions from the Los Angeles (LA) were decreasing on average during 2011-2020, but not as much as originally thought. Atmospheric methane is potent Earth warming greenhouse gas often emitted from natural gas leaks as well as natural sources. It is a powerful greenhouse gas with about 80 times higher global warming potential than carbon dioxide (CO₂) over a 20-year period. Because of its relatively short lifetime (~12 years), reducing emissions of CH₄ can have an immediate contribution to slowing global warming. With the strong warming potential and the shorter lifetime, CH₄ is a key target for greenhouse gas emission reduction strategies.

"The "bottom-up" inventory approach is an established common way to track emission changes, but the "top-down" atmospheric measurement-based approach can further confirm the emission estimates and also detect biases in them, if they exist, as shown in this study," said Dr. Oda. The bottom-up inventory emission estimates are often based on survey activity data and the conversion factor called "emission factor (EF)." Because of the limited availability of the activity data and EF, estimates could be biased. In contrast, the "top down" approach of measuring methane levels in the atmosphere directly translates the measured atmospheric methane levels and the change into emission estimates. "The two approaches are complementary, and by combining them, we can get more reliable and tailored emission information," said Dr. Oda.

"This is a great demonstration of how Earth Observation can support climate mitigation for subnational climate actions and achieving the climate reduction target," said Dr. Paul Palmer, Professor at the University of Edinburgh, UK, and a co-author of the study. Since 2021, USRA, as an admitted observer NGO, has sent its delegate to the United Nations Framework Convention on Climate Change (UNFCCC) and has facilitated important Earth-observation-based mitigation conversations at the past two COP meetings in Glasgow, UK, in 2021 (COP26) and Sharm El Shaikh, Egypt, in 2022 (COP27). Dr. Oda will lead USRA's COP delegation in 2023 to COP28 to be held in Dubai, UAE, later this year.

About USRA
Founded in 1969, under the auspices of the National Academy of Sciences at the request of the U.S. Government, the Universities Space Research Association (USRA), is a nonprofit corporation chartered to advance space-related science, technology and engineering. USRA operates scientific institutes and facilities, and conducts other major research and educational programs. It engages the university community and employs in-house scientific leadership, innovative research and development, and project management expertise. More information about USRA is available at www.usra.edu.

Additional Resource: https://www.nature.com/articles/s41467-023-40964-w