Attribution of the 2020 surge in atmospheric methane by inverse analysis
of GOSAT observations
Abstract
Atmospheric methane mixing ratio rose by 15 ppbv between 2019 and 2020,
the fastest growth rate on record. We conduct a global inverse analysis
of 2019-2020 GOSAT satellite observations of atmospheric methane to
analyze the combination of sources and sinks driving this surge. The
atmospheric methane growth rate increased by 31 Tg a-1 from 2019 to
2020, representing a 36 Tg a-1 forcing on the methane budget away from
steady state. 86% of the forcing in the base inversion is from
increasing emissions (82 ± 18% in the 9-member inversion ensemble), and
14% is from decrease in tropospheric OH. Half of the increase in
emissions is from Africa (15 Tg a-1) and appears to be driven by wetland
inundation. There is also a large relative increase in emissions from
Canada and Alaska (4.8 Tg a-1 , 24%) that could be driven by
temperature sensitivity of boreal wetland emissions.