Air pollution affects climate through various complex interactions¹. It perturbs the Earth’s radiative energy balance and alters the atmospheric oxidation capacity, which determines the lifetimes of short-lived climate forcers, such as methane¹. A key mechanism in this dynamic is the impact of air pollutants on the hydroxyl radical (OH), the most important oxidant in the troposphere, which accounts for approximately 90% of the methane chemical sink². However, a comprehensive quantification of the interactions between air pollutants, OH and methane over decadal timescales remains incomplete². Here we develop an integrated observation-driven and model-driven approach to quantify how variations in key air pollutants influence the methane chemical sink and alter the methane budget. Our results indicate that, from 2005 to 2021, enhanced tropospheric ozone, increased water vapour and decreased carbon monoxide levels collectively contributed to a 1.3–2.0 Tg year⁻¹ increase per year in the global methane sink, thereby buffering atmospheric methane growth rates. This increase in the methane sink was primarily concentrated in tropical regions and exhibited a north–south asymmetry. Periods of high methane growth were typically linked to abrupt OH level declines driven by fluctuations in air pollutants, especially during extreme events such as mega wildfires and the COVID-19 pandemic. Our study suggests a trade-off between O₃ pollution control and methane removal mediated by OH and highlights the risk of increasing carbon monoxide emissions from widespread wildfires.

空气污染通过各种复杂的相互作用影响气候 ¹.它扰乱了地球的辐射能量平衡并改变了大气氧化能力，这决定了甲烷 ¹ 等短寿命气候因素的寿命。这种动态的一个关键机制是空气污染物对羟基自由基 （OH） 的影响，羟基自由基 （OH） 是对流层中最重要的氧化剂，约占甲烷化学汇的 90%²。然而，在年代际时间尺度上对空气污染物、OH 和甲烷之间相互作用的全面量化仍然不完整 ²。在这里，我们开发了一种综合的观测驱动和模型驱动方法来量化关键空气污染物的变化如何影响甲烷化学汇并改变甲烷预算。我们的结果表明，从 2005 年到 2021 年，对流层臭氧的增加、水蒸气的增加和一氧化碳水平的降低共同导致全球甲烷汇每年增加 1.3-2.0 Tg ^year-1，从而缓冲大气甲烷增长率。甲烷汇的增加主要集中在热带地区，并表现出南北不对称性。甲烷高速增长时期通常与空气污染物波动导致的 OH 水平突然下降有关，尤其是在特大野火和 COVID-19 大流行等极端事件期间。我们的研究表明，O₃ 污染控制和 OH 介导的甲烷去除之间存在权衡，并强调了大范围野火导致一氧化碳排放增加的风险。