The Covenant of Mayors (CoM) is a successful European initiative which encourages local authorities to be proactive in fighting climate change. Recently, it expanded to cover adaptation and energy access/poverty and became a global initiative. In this study we investigate an additional perspective: synergies and trade-offs between climate and air quality. Signatories pledge to reduce their Greenhouse gas (GHG) emissions and voluntarily report their emissions, energy consumption and the measures that they carry out to reach their goals. We develop a methodology to estimate air pollutant emissions corresponding to CO₂ emissions CoM signatories report, using information they already submit and national estimates of air pollutant emission factors. The methodology is applied to over 1600 signatories in Europe, representing over 80 million inhabitants. Results show that, in general, signatories are reducing both types of emissions. However, there are also cases where emissions increase. We explore the reasons behind these changes and highlight the role of technological improvement. This work calls for an increased coherence between climate and air quality plans at the local scale and provides a first step and a tool to support signatories, even the smallest ones, to move in this direction.

市长盟约（CoM）是一项成功的欧洲倡议，鼓励地方当局积极应对气候变化。最近，它扩展到涵盖适应和能源获取/贫困，并成为一项全球倡议。在这项研究中，我们研究了另一个视角：气候与空气质量之间的协同作用和权衡。签署方保证减少其温室气体（GHG）排放，并自愿报告其排放，能源消耗以及为实现其目标而采取的措施。我们开发了一种方法来估算与CO ₂相对应的空气污染物排放排放CoM签署者使用他们已经提交的信息和国家对空气污染物排放因子的估算进行报告。该方法适用于欧洲的1600多个签署国，代表了8000万居民。结果表明，总体而言，签署国正在减少两种排放。但是，在某些情况下排放也会增加。我们探索了这些变化背后的原因，并强调了技术改进的作用。这项工作要求在地方范围内提高气候与空气质量计划之间的一致性，并为支持签字国（甚至最小的签字国）朝这个方向发展提供了第一步和工具。