CARE-C collaborative research published on understanding methane emissions from fossil fuels

A recent study by CARE-C researchers of the Cyprus Institute, affiliate scientists from Laboratoire des Sciences du Climat et de l’Environnement (LSCE) and others, focusing on analysing methane emissions from oil, gas and coal sectors across inventories and atmospheric inversions, in the Eastern Mediterranean and Middle East region, was published in Nature’s Communications Earth Environment Journal.

Methane, a potent greenhouse gas, is more than 25 times as effective as CO2 in trapping heat. Fossil fuel production is a significant source of methane emissions, with reported values varying widely (80 to 146 Tg/yr). This uncertainty hampers the assessment of global efforts, such as the Global Methane Pledge, to control methane emissions. A recent study by researchers involved in the EMME-CARE and Global Carbon projects focused on major fossil-fuel producers in the Eastern Mediterranean and Middle East, aiming to identify and address discrepancies in methane emission estimates. The study supports the EMME-CARE project’s overall goal of advancing climate and atmosphere research in the region.

The emission estimates analysed in this research include 8 bottom-up and 12 top-down inventories. Bottom-up estimates combine fossil-fuel production data and emission factors, while top-down estimates use methane concentration observations to simulate releases through complex Earth atmosphere models. This iterative process adjusts the initial “prior inventory” from a bottom-up source until observed and simulated concentrations align. In this study, a subset of inversion-based emissions relies on CH4 concentrations from the GOSAT satellite, part of the European Space Agency’s Third-Party Missions Programme.

Analysis of these inventories reveals large disagreements, primarily from the oil and gas sector, in both the value of annual emissions averaged over the last decade (2011-2020) and the rate of change in annual emissions from 2000 to 2020. Notable variations are observed for Russia, Kazakhstan, Iran, and Arabian Peninsula countries. The study emphasizes the need for a nuanced approach, as using a single inventory may misrepresent future emissions reductions.  Furthermore, differences in bottom-up inventories arise from variations in inputs, particularly from the use of different data sources for emission factors. The results also highlighted the interdependency among the inventories in regard to data sources.

The study specifically compares estimates from national bottom-up inventories submitted to the United Nations Framework Convention on Climate Change (UNFCCC) with other bottom-up and top-down inventories. Overall, countries with a significant share of oil and gas activity reported much lower values in their UNFCCC reports. Annex I countries (as defined by UNFCCC), reporting annual emission time-series, often undergo frequent revisions due to methodological updates, superseding previous estimates. Additionally, major oil and gas producing non-Annex I countries such as Iran, Turkmenistan, Venezuela, and countries in the Arabian Peninsula either lack or have very outdated reported values.

Lastly, the study explores how prior inventory affects emissions values in top-down inventories, which conduct inversion calculations for broad sectors. To allocate emissions within sub-categories, top-down inventories depend on sub-sectoral contributions from the prior inventory. The study reveals that the choice of prior inventory significantly impacts emission values at the sub-sectoral level, particularly for countries with limited observations. This underscores the necessity for more robust methods in calculating sub-sectoral emissions using top-down approaches.

 Overall, the research consolidates methane emissions from fossil fuel production, providing a critical assessment of global inventories. It emphasizes the need for improved accuracy, particularly in the oil and gas sector, to facilitate effective monitoring and reduction of anthropogenic methane emissions. The study calls for regular updates from countries lacking official estimates to UNFCCC and highlights the influence of prior inventory on top-down estimates, emphasizing the importance of refining sub-sectoral emissions evaluation.

Original Publication: Tibrewal, K., Ciais, P., Saunois, M. et al. Assessment of methane emissions from oil, gas and coal sectors across inventories and atmospheric inversions. Commun Earth Environ 5, 26 (2024).

EMMECARE has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 856612 and the Cyprus Government.