Abstract
Abstract. We use a global inverse model, satellite data and flask measurements to estimate methane (CH4) emissions from South America, Brazil and the basin of the Amazon River for the period 2010–2018. We find that emissions from Brazil have risen during this period, most quickly in the eastern Amazon basin, and that this is concurrent with increasing surface temperatures in this region. Brazilian CH4 emissions rose from 49.8 ± 5.4 Tg yr−1 in 2010–2013 to 55.6 ± 5.2 Tg yr−1 in 2014–2017, with the wet season of December–March having the largest positive trend in emissions. Amazon basin emissions grew from 41.7 ± 5.3 to 49.3 ± 5.1 Tg yr−1 during the same period. We derive no significant trend in regional emissions from fossil fuels during this period. We find that our posterior distribution of emissions within South America is significantly and consistently changed from our prior estimates, with the strongest emission sources being in the far north of the continent and to the south and south-east of the Amazon basin, at the mouth of the Amazon River and nearby marsh, swamp and mangrove regions. We derive particularly large emissions during the wet season of 2013/14, when flooding was prevalent over larger regions than normal within the Amazon basin. We compare our posterior CH4 mole fractions, derived from posterior fluxes, to independent observations of CH4 mole fraction taken at five lower- to mid-tropospheric vertical profiling sites over the Amazon and find that our posterior fluxes outperform prior fluxes at all locations. In particular the large emissions from the eastern Amazon basin are shown to be in good agreement with independent observations made at Santarém, a location which has long displayed higher mole fractions of atmospheric CH4 in contrast with other basin locations. We show that a bottom-up wetland flux model can match neither the variation in annual fluxes nor the positive trend in emissions produced by the inversion. Our results show that the Amazon alone was responsible for 24 ± 18 % of the total global increase in CH4 flux during the study period, and it may contribute further in future due to its sensitivity to temperature changes.
Highlights
Methane (CH4), a strong greenhouse gas emitted from a variety of anthropogenic and natural sources, is second only to carbon dioxide (CO2) in its importance regarding the anthropogenic radiative forcing contributing to Earth’s climate change (Myhre et al, 2013)
Average Gases Observing Satellite (GOSAT) XCH4 values over South America since 2009 show that XCH4 column mole fractions were largest over the west of the continent, in the northwest (Fig. 2)
Webb et al (2016) found that comparisons between the flight-based observations and a previous version of the GOSAT XCH4 used in this study showed that the GOSAT values were larger than equivalents estimated using the flight data at Alta Floresta (ALF) but that the discrepancy was much smaller at SAN
Summary
Methane (CH4), a strong greenhouse gas emitted from a variety of anthropogenic and natural sources, is second only to carbon dioxide (CO2) in its importance regarding the anthropogenic radiative forcing contributing to Earth’s climate change (Myhre et al, 2013). With an atmospheric lifetime of approximately 9 years (Prather et al, 2012), CH4 is a potentially important species for short-term gains in mitigation of anthropogenic climate change (Shindell et al, 2012). The geographical distribution and sectoral attribution of methane emissions, and the inter-annual variation of these sources, are uncertain (Saunois et al, 2016; Schaefer, 2019). This leads to difficulties in assessing potential emission mitigation strategies, hampering our ability to meet and assess the criteria for limiting the global temperature increase put forward as part of the Paris climate agreement (Nisbet et al, 2019)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
