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.Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 52 is May 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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发生反应，在很大程度上控制对流层的自清洁能力。 OH 浓度由本地竞争的生产和损失过程决定。由于缺乏强有力的观测约束，模型在平衡这些过程的方式上有所不同，因此过去和未来 OH 变化的迹象是不确定的。在气候变暖的情况下，由于对水蒸气的依赖，羟基产量将会增加，但羟基甲烷损失更快，部分抵消了这一影响。天气敏感排放也可能会增加，尽管它们对全球平均 OH 的净影响取决于源气体（氮氧化物）和汇气体（活性碳）之间的平衡。闪电活动会增加 OH，但其对气候变暖的反应尚不确定。为了能够可靠地预测 OH，我们建议努力减少动力学反应、测量和建模的 OH、过去 OH 浓度的代理以及源气体和汇气体排放的不确定性。 ▪ OH 的寿命最多只有几秒钟，但它受到内部气候变化的强烈调节，这对解释甲烷的趋势具有重要意义。 ▪ 改善关键反应的动力约束将增强人们对区域和全球卫生预算以及卫生部门应对气候变化的信心。 ▪ 未来的OH 变化将取决于涉及对天气敏感的化学和排放的不确定性和补偿过程，以及人类的选择。 ▪ 气候变化的技术解决方案可能会影响对流层氧化能力，在实施前值得进一步研究。《地球与行星科学年度评论》第 52 卷的预计最终在线发布日期为 2024 年 5 月。请参阅 http://www.annualreviews 。org/page/journal/pubdates 了解修订后的估计。