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2010-2015 North American methane emissions, sectoral contributions, and trends: A high-resolution inversion of GOSAT observations of atmospheric methane

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journal contribution
posted on 04.05.2021, 09:12 by JD Maasakkers, DJ Jacob, MP Sulprizio, TR Scarpelli, H Nesser, J Sheng, Y Zhang, X Lu, A Anthony Bloom, KW Bowman, JR Worden, R J. Parker
We use 2010 2015 Greenhouse Gases Observing Satellite (GOSAT) observations of atmospheric methane columns over North America in a high-resolution inversion of methane emissions, including contributions from different sectors and their trends over the period. The inversion involves an analytical solution to the Bayesian optimization problem for a Gaussian mixture model (GMM) of the emission field with up to 0:5-0:625 resolution in concentrated source regions. The analytical solution provides a closedform characterization of the information content from the inversion and facilitates the construction of a large ensemble of solutions exploring the effect of different uncertainties and assumptions in the inverse analysis. Prior estimates for the inversion include a gridded version of the Environmental Protection Agency (EPA) Inventory of US Greenhouse Gas Emissions and Sinks (GHGI) and the WetCHARTs model ensemble for wetlands. Our best estimate for mean 2010 2015 US anthropogenic emissions is 30.6 (range: 29.4 31.3) Tg a-1, slightly higher than the gridded EPA inventory (28.7 (26.4 36.2) Tg a-1). The main discrepancy is for the oil and gas production sectors, where we find higher emissions than the GHGI by 35% and 22 %, respectively. The most recent version of the EPA GHGI revises downward its estimate of emissions from oil production, and we find that these are lower than our estimate by a factor of 2. Our best estimate of US wetland emissions is 10.2 (5.6 11.1) Tg a-1, on the low end of the prior WetCHARTs inventory uncertainty range (14.2 (3.3 32.4) Tg a-1), which calls for better understanding of these emissions. We find an increasing trend in US anthropogenic emissions over 2010 2015 of 0.4%a-1, lower than previous GOSAT-based estimates but opposite to the decrease reported by the EPA GHGI. Most of this increase appears driven by unconventional oil and gas production in the eastern US. We also find that oil and gas production emissions in Mexico are higher than in the nationally reported inventory, though there is evidence for a 2010 2015 decrease in emissions from offshore oil production.

Funding

This research was funded by the NASA Car-bon Monitoring System (CMS) program. Robert J. Parker is funded via the UK National Centre for Earth Observation (NCEO) (grantnos. nceo020005 and NE/N018079/1).

History

Citation

Atmos. Chem. Phys., 21, 4339–4356, https://doi.org/10.5194/acp-21-4339-2021, 2021.

Author affiliation

School of Physics and Astronomy

Version

VoR (Version of Record)

Published in

Atmospheric Chemistry and Physics

Volume

21

Issue

6

Pagination

4339 - 4356

Publisher

Copernicus Publications

issn

1680-7316

eissn

1680-7324

Acceptance date

07/01/2021

Copyright date

2021

Available date

04/05/2021

Language

English

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