Urban agglomerates play a crucial role in reaching global climate objectives. Many cities have committed to reducing their greenhouse gas emissions, but current emission trends remain unverifiable. Atmospheric monitoring of greenhouse gases offers an independent and transparent strategy to measure urban emissions. However, careful design of the monitoring network is crucial to be able to monitor the most important sectors as well as adjust to rapidly changing urban landscapes. Our study of Paris and Munich demonstrates how climate action plans, carbon emission inventories, and urban development plans can help design optimal atmospheric monitoring networks. We show that these two European cities display widely different trajectories in space and time, reflecting different emission reduction strategies and constraints due to administrative boundaries. The projected carbon emissions rely on future actions, hence uncertain, and we demonstrate how emission reductions vary significantly at the sub-city level. We conclude that quantified individual cities’ climate actions are essential to construct more robust emissions trajectories at the city scale. Also, harmonization and compatibility of plans from various cities are necessary to make inter-comparisons of city climate targets possible. Furthermore, dense atmospheric networks extending beyond the city limits are needed to track emission trends over the coming decades.

中文翻译：

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从政治承诺到气候缓解计划的定量绘制：两个欧洲城市的比较

城市群在实现全球气候目标方面发挥着至关重要的作用。许多城市已承诺减少温室气体排放，但目前的排放趋势仍然无法核实。温室气体的大气监测为测量城市排放提供了独立且透明的策略。然而，监测网络的仔细设计对于能够监测最重要的部门以及适应快速变化的城市景观至关重要。我们对巴黎和慕尼黑的研究展示了气候行动计划、碳排放清单和城市发展计划如何帮助设计最佳的大气监测网络。我们发现，这两个欧洲城市在空间和时间上表现出截然不同的轨迹，反映出不同的减排策略和由于行政边界的限制。预计的碳排放量取决于未来的行动，因此具有不确定性，我们展示了次城市层面的减排量如何存在显着差异。我们的结论是，量化各个城市的气候行动对于在城市规模上构建更稳健的排放轨迹至关重要。此外，各城市规划的协调和兼容性对于实现城市气候目标的相互比较也是必要的。此外，需要延伸到城市范围之外的密集大气网络来跟踪未来几十年的排放趋势。