Satellite quantification of methane emissions from South American countries: A high-resolution inversion of TROPOMI and GOSAT observations

Abstract

Abstract. We use 2021 TROPOMI and GOSAT satellite observations of atmospheric methane in an analytical inversion to quantify national methane emissions from South America at up to 25 km × 25 km resolution. From the inversion, we derive optimal posterior estimates of methane emissions correcting the national anthropogenic emission inventories reported by individual countries to the United Nations Framework Convention on Climate Change (UNFCCC) and taken here as prior estimates. We also evaluate two alternative wetland emission inventories (WetCHARTs and LPJ-wsl) as prior estimates. Our best posterior estimates for wetland emissions are consistent with previous inventories for the Amazon but lower for the Pantanal and higher for the Parana. Our best posterior estimate of South American anthropogenic emissions is 48 (41–56) Tg a^-1, where numbers in parentheses are the range from our inversion ensemble. This is 55 % higher than UNFCCC reports and is dominated by livestock (65 % of anthropogenic total). We find that TROPOMI and GOSAT observations can effectively optimize and separate national emissions by sector for 10 of the 13 countries and territories in the region, 7 of which account for 93 % of continental anthropogenic emissions: Brazil (19 (16–23) Tg a⁻¹), Argentina (9.2 (7.9–11) Tg a⁻¹ ), Venezuela (7.0 (5.5-9.9) Tg a⁻¹), Colombia (5.0 (4.4–6.7) Tg a⁻¹), Peru (2.4 (1.6–3.9) Tg a⁻¹), Bolivia (0.96 (0.66–1.2) Tg a⁻¹), and Paraguay (0.93 (0.88 – 1.0) Tg a⁻¹). Our estimates align with UNFCCC reports for Brazil, Bolivia, and Paraguay, but are significantly higher for other countries. Emissions in all countries are dominated by livestock (mainly enteric fermentation) except for oil/gas in Venezuela and landfills in Peru. Methane intensities from the oil/gas industry are high in Venezuela (33 %), Colombia (6.5 %) and Argentina (5.9 %). Country-average emission factors for enteric fermentation from cattle in UNFCCC reports are in the range 46–60 kg head^-1 a^-1, close to the IPCC Tier 1 estimate which is mostly based on data from Brazil. Our inversion yields cattle enteric fermentation emission factors consistent with the UNFCCC reports for Brazil and Bolivia but a factor of two higher for other countries. The discrepancy for Argentina can be corrected by using IPCC Tier 2 emission estimates accounting for high milk production.