Methane emission reductions slow stratospheric ozone recovery by amplifying the potency of ozone depleting substances.

Reducing methane emissions is important for restricting surface temperature increases. However, methane also influences stratospheric ozone, and its recovery, via chemical and radiative processes. Using the United Kingdom Earth System Model’s state-of-the-art methane emission- driven capability, we examine the impact of methane emission reductions of varying magnitude and timing on stratospheric ozone recovery under future scenarios with high (SSP3-7.0) and low (SSP1-2.6) surface warming. Despite beneficial surface temperature reductions, decreasing methane emissions slows total column ozone (TCO) recovery. By 2100, globally-averaged TCO is 2.4% lower in SSP3-7.0LowCH4 (1200 parts-per-billion surface CH4 mole fraction) than SSP370 (2260 parts-per-billion). . Methane reductions drive increased ozone destruction in the mid-upper stratosphere, via interactions with compounds derived from nitrous oxide (N2O) and halocarbons, and reduced production in the troposphere and lower stratosphere. Therefore, the ongoing efforts to reduce N2O and halocarbons emissions (which bring climate co-benefits) will become more important if methane emission reductions occur.