Emissions from the Oil and Gas Sectors, Coal Mining and Ruminant Farming Drive Methane Growth over the Past Three Decades

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 Methane (CH₄) is an important greenhouse gas and plays a significant role in tropospheric and stratospheric chemistry. Despite the relevance of methane (CH₄) in human-induced climate change and air pollution chemistry, there is no scientific consensus on the causes of changes in its growth rates and variability over the past three decades. We use a well-validated chemistry-transport model for simulating CH₄ concentration and estimation of regional CH₄ emissions by inverse modelling for the period of 1988-2016. The control simulations are performed using a seasonally varying hydroxyl (OH) concentrations and assumed no interannual variability. Using inverse modelling of atmospheric observations, emission inventories, a wetland model, and a δ¹³C-CH₄ box model, we show that reductions in emissions from Europe and Russia since 1988, particularly from oil-gas exploitation and enteric fermentation, led to decreased CH₄ growth rates in the 1990s. This period was followed by a quasi-stationary state of CH₄ in the atmosphere during the early 2000s. CH₄ resumed growth from 2007, which we attribute to increases in emissions from coal mining mainly in China and intensification of ruminant farming in tropical regions. A sensitivity simulation using interannually varying OH shows that regional emission estimates by inversion are unaffected for the mid- and high latitude areas. We show that meridional shift in CH₄ emissions toward the lower latitudes and the increase in CH₄ loss by hydroxyl (OH) over the tropics finely balance out, which keep the CH₄ gradients between the southern hemispheric tropical and polar sites relatively unchanged during 1988-2016. The latitudinal emissions shift is confirmed using the global distributions of the total column CH₄ observations by satellite remote sensing. There is no evidence of emission enhancement due to climate warming, including the boreal regions, during our analysis period. These findings highlight key sectors for effective emission reduction strategies toward climate change mitigation.