Spaceborne assessment of the Soviet Union's role in the 1990s methane slowdown

Methane is the second most important anthropogenic greenhouse gas, amounting to 60% of the radiative forcing from CO2 since pre-industrial times based on emitted compound. Global atmospheric methane concentrations rose by 10-15 ppb/yr in the 1980s before abruptly slowing to 2-8 ppb/yr in the early 1990s. This period in the 1990s is known as the ``methane slowdown'' and has been attributed to the collapse of the former Soviet Union (USSR) in 1991, which may have decreased the methane emissions from oil and gas operations. Here we develop a methane plume detection system based on probabilistic deep learning and human-labelled training data. We use this method to detect methane plumes from Landsat 5 satellite observations over Turkmenistan from 1986 to 2011. We find an increase in both the frequency of methane plume detections and the magnitude of methane emissions following the collapse of the USSR in 1991. We estimate a national leak rate from oil and gas infrastructure in Turkmenistan of more than 10% at times, which suggests the socioeconomic turmoil led to a lack of oversight and widespread infrastructure failure in the oil and gas sector. Our results contradict the theory that the 1990s methane slowdown was driven by the collapse of the USSR, which we find led to an increase in methane emissions.