The hydroxyl radical (OH) largely controls the tropospheric self-cleansing capacity by reacting with gases harmful to the environment and human health. OH concentrations are determined locally by competing production and loss processes. Lacking strong observational constraints, models differ in how they balance these processes, such that the sign of past and future OH changes is uncertain. In a warmer climate, OH production will increase due to its water vapor dependence, partially offset by faster OH-methane loss. Weather-sensitive emissions will also likely increase, although their net impact on global mean OH depends on the balance between source (nitrogen oxides) and sink (reactive carbon) gases. Lightning activity increases OH, but its response to climate warming is of uncertain sign. To enable confident projections of OH, we recommend efforts to reduce uncertainties in kinetic reactions, in measured and modeled OH, in proxies for past OH concentrations, and in source and sink gas emissions. ▪OH is strongly modulated by internal climate variability despite its lifetime of a few seconds at most, with implications for interpreting trends in methane.▪Improved kinetic constraints on key reactions would strengthen confidence in regional and global OH budgets, and in the response of OH to climate change.▪Future OH changes will depend on uncertain and compensating processes involving weather-sensitive chemistry and emissions, plus human choices.▪Technological solutions to climate change will likely impact tropospheric oxidizing capacity and merit further study prior to implementation.

中文翻译：

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气候和对流层氧化能力


羟基自由基 （OH） 通过与对环境和人类健康有害的气体反应，在很大程度上控制对流层的自清洁能力。OH 浓度由竞争性生产和损失过程在局部确定。由于缺乏强大的观测约束，模型在如何平衡这些过程方面有所不同，因此过去和未来 OH 变化的迹象是不确定的。在温暖的气候中，由于氢氯甲烷对水蒸气的依赖性，其产量将增加，部分被氢氯甲烷损失更快所抵消。对天气敏感的排放也可能会增加，尽管它们对全球平均 OH 的净影响取决于源（氮氧化物）和汇（活性碳）气体之间的平衡。闪电活动增加了 OH，但它对气候变暖的反应尚不确定。为了实现对 OH 的可靠预测，我们建议努力减少动力学反应、测量和建模 OH、过去 OH 浓度的替代以及源和汇气体排放的不确定性。▪尽管 OH 的生命周期最多只有几秒钟，但其生命周期仍受内部气候变化的强烈调节，这对解释甲烷的趋势有影响。▪改进关键反应的动力学约束将增强对区域和全球 OH 预算以及 OH 对气候变化的响应的信心。▪未来的 OH 变化将取决于涉及天气敏感化学和排放的不确定和补偿过程， 加上人类的选择.▪气候变化的技术解决方案可能会影响对流层的氧化能力，值得在实施之前进一步研究。