Would methane levels fall without methane removal technologies?

If methane emissions are cut aggressively enough, that would lower methane concentrations by itself, but not enough to prevent methane from further contributing to global warming.  

Methane has a relatively short half-life in the atmosphere. Theoretically, methane concentrations would fall if emissions suddenly ceased.  But as a practical matter, methane emissions won’t suddenly stop.  On the contrary, methane emissions from hard-to-mitigate sources, both anthropogenic and natural, are rising fast.  

Combined with aggressive emissions cuts, methane removal would help reverse the rapid, ongoing increase in atmospheric methane and avoid significant methane-induced global warming.

The fossil fuel industry emits about 20% of anthropogenic methane, half of which comes from coal mines.  The International Energy Agency report Net Zero by 2050  calls for an immediate end to oil and gas exploration, and  points out “early results from satellite data show leaky oil and gas industry infrastructure is responsible for far more of the methane in the atmosphere than previously thought.” 

While we agree with the IEA that getting off fossil fuels is urgent, Methane Action believes that the goal of net zero by 2050 isn’t sufficient to avoid catastrophic warming.  We must revise global targets beyond net zero, and commit to net-negative strategies now.

Ending reliance on fossil fuels is crucial, but it’s worth noting it will have a complex impact on atmospheric methane levels.  As clean energy replaces fossil fuels, methane emissions from the fossil fuel sector, as well as carbon dioxide and other GHG emissions, may decrease.  Nitrogen oxide and sulfur dioxide pollution will also fall, which will improve air quality and public health. 

But reducing nitrogen oxides and sulfur oxides pollution will also reduce atmospheric methane oxidation.  That’s because nitrogen oxides stimulate production of hydroxyl radicals (°OH)   in the atmosphere, which drive 90% of natural methane oxidation. To some degree, sulfates produced by SOx also artificially suppress methane emissions, and sulfate aerosols have a cooling effect, so their reduction will have a warming effect. Decreasing NOx and SOx pollution, while beneficial, will tend to increase atmospheric methane. 

Stopping new oil and gas exploration, replacing fossil fuels with clean energy, and capping disused oil and gas wells are all critically important.  But they will not be sufficient by themselves to lower atmospheric methane levels and avoid methane-induced warming.  For that, we will need a both-and approach:  both reducing methane emissions from all sources, and  developing and deploying methane removal.

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