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. 2022 Jan;28(1):182-200.
doi: 10.1111/gcb.15901. Epub 2021 Oct 27.

Regional trends and drivers of the global methane budget

Ann R Stavert  1   2 , Marielle Saunois  3 , Josep G Canadell  1   2 , Benjamin Poulter  4 , Robert B Jackson  5 , Pierre Regnier  6 , Ronny Lauerwald  3   6   7 , Peter A Raymond  8 , George H Allen  9 , Prabir K Patra  10   11 , Peter Bergamaschi  12 , Phillipe Bousquet  3 , Naveen Chandra  13 , Philippe Ciais  3 , Adrian Gustafson  14   15 , Misa Ishizawa  13 , Akihiko Ito  13 , Thomas Kleinen  16 , Shamil Maksyutov  13 , Joe McNorton  17 , Joe R Melton  18 , Jurek Müller  19 , Yosuke Niwa  13 , Shushi Peng  3 , William J Riley  20 , Arjo Segers  21 , Hanqin Tian  22 , Aki Tsuruta  23 , Yi Yin  24 , Zhen Zhang  25 , Bo Zheng  3 , Qianlai Zhuang  26
Affiliations

Regional trends and drivers of the global methane budget

Ann R Stavert et al. Glob Chang Biol. 2022 Jan.

Abstract

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 during 2000-2017. Here, we decompose the global budget into 19 regions (18 land and 1 oceanic) and five key source sectors to spatially attribute the observed global trends. A comparison of top-down (TD) (atmospheric and transport model-based) and bottom-up (BU) (inventory- and process model-based) CH4 emission 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 totaling >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 and 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.

Keywords: anthropogenic emissions; bottom-up; methane emissions; natural emissions; regional; source sectors; top-down.

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Conflict of interest statement

The authors declare that there are no competing financial interests.

Figures

FIGURE 1
FIGURE 1
The locations of the surface (triangle) and ground‐based profile (circle) observation sites and GOSAT XCH4 data density and extent (number of data points per grid cell per month for NIES full physics retrievals) for 2014. Grid cells are 2.5 × 2.5°. Note that many of the in situ sites are not operational or are not reporting data to the Global Atmospheric Watch repository. Also note that many of the GOSAT grids do not have uniform data coverage in all months as the instrument cannot see through the cloud covered areas and during polar nights
FIGURE 2
FIGURE 2
Boxplots of the total source estimates for the most recent decade (2008–2017) for each region for the bottom‐up (BU—red boxes) and top‐down surface sites only (TD SURF—blue boxes). The priors used in the TD SURF estimate are also shown (empty boxes). The box represents the 25th to 75th percentile range, “x” represents the outliers and the whiskers show the minimum and maximum values (outliers excluded)
FIGURE 3
FIGURE 3
(a) Natural (green) emissions by region, (b) mean anthropogenic (brown), and (c) mean anthropogenic proportion as a percentage of total regional emissions (brown) in Tg CH4 yr−−1 for 2008–2017. Bottom‐up (BU) estimates are shown as filled boxes and top‐down surface sites only (TD SURF) as open boxes. The box represents the 25th to 75th percentile range, “x” represents the outliers and the whiskers show the minimum and maximum values (outliers excluded)
FIGURE 4
FIGURE 4
The sectorial budget breakdown for each region in Tg CH4 yr−1 for the most recent decade (2008–2017) and a map of the 18 land regions used in this study. Each panel shows methane emissions for the five key sectors, from left to right: Wetlands, Biomass burning and biofuels, Fossil fuels, Agriculture & waste, and Other natural (including inland waters). Top‐down estimates are shown on the left as light‐colored boxes and bottom‐up estimates on the right as dark‐colored boxes. Sectoral emission estimates based on less than 5 data points are shown as open boxes and those with 5 or greater data points are shown as filled boxes. The box represents the 25th to 75th percentile range, “x” represents the outliers, and the whiskers show the minimum and maximum values (outliers excluded)
FIGURE 5
FIGURE 5
Annual estimates of total CH4 emissions in Tg CH4 yr−1 for each of the 18 land regions, the ocean region and the global total over 2000–2017. Bottom‐up (blue) and top‐down (red—surface sites only, magenta—surface sites and satellite data). Thick lines indicate the mean estimate, whereas thin lines represent individual estimates
FIGURE 6
FIGURE 6
Yearly mean regional and global agriculture and waste (orange), biomass burning and biofuel (red), fossil fuels (black), other natural (blue) and wetland (green) fluxes in Tg CH4 yr−1 over 2000 to 2017. The mean of the bottom‐up estimates are shown as a solid line, the mean of the top‐down (surface sites only) as a dashed line and the mean of the top‐down estimates including GOSAT data as a dotted line
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