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Regional trends and drivers of the global methane budget

Authors: 
Stavert AR et al.
Year: 
2021
Journal: 
Global Change Biology
Journal Volume/Pages: 
in press

The ongoing development of the Global Carbon Project (GCP) global methane (CH4) budget shows a continuation of increasing CH4 emissions and CH4 accumulation in the atmosphere over 2000-2017. Here we decompose the global budget into 19 regions (18 land and one oceanic) and five key source sectors to spatially attribute the observed global trends. A comparison of top-down (atmospheric and transport model-based) and bottom-up (inventory- and process model-based) CH4 emissions estimates demonstrates robust temporal trends with CH4 emissions increasing in 16 of the 19 regions. Five regions - China, Southeast Asia, USA, South Asia, and Brazil - account for > 40% of the global total emissions (their anthropogenic and natural sources together totalling > 270 Tg CH4 yr-1 in 2008-2017). Two of these regions, China and South Asia, emit predominantly anthropogenic emissions (> 75%) and together emit more than 25% of global anthropogenic emissions. China and the Middle East show the largest increases in total emission rates over the 2000 to 2017 period with regional emissions increasing by > 20%. In contrast, Europe and Korea & Japan, show a steady decline in CH4 emission rates, with total emissions decreasing by ~10% between 2000 and 2017. Coal mining, waste (predominantly solid waste disposal) and livestock (especially enteric fermentation) are dominant drivers of observed emissions increases while declines appear driven by a combination of waste and fossil emission reductions. As such, together these sectors present the greatest risks of further increasing the atmospheric CH4 burden and the greatest opportunities for greenhouse gas abatement.

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