Fig. 3: Decadal decreasing trend of CH4 emissions.
From: Decadal decrease in Los Angeles methane emissions is much smaller than bottom-up estimates
a Monthly CH4 emissions, estimated based on the ODIAC CO2 inventory, from Sept. 2011 to Dec. 2021 in the LA basin and fitting using a statistical model (Eq. (4)) that consists of a linear component and a seasonal component by harmonic functions. The linear component is extracted and shown in blue. The slope of this linear component is −0.35 ± 0.20 Gg/month. b The same as (a) but for monthly CH4 emissions, estimated based on the CARB CO2 inventory. The slope of this linear component is −0.68 ± 0.19 Gg/month. The error bars represent the estimation error (1σ) of the monthly emissions. c Interannual trend extracted from the Ensemble Empirical Mode Decomposition (EEMD) analysis based on the monthly CH4 emissions estimated using the ODIAC CO2 inventory. The beginning and end of the EEMD curves are influenced by edge effects for approximately a year at each end. The uncertainty band is ± 1σ.
