From political pledges to the quantitative mapping of climate mitigation plans: comparison of two European cities

Urban agglomerations 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. The quantification of mitigation policies is often incomplete or unavailable, raising serious concerns about how and if climate mitigation targets will be achieved. To support the effective traceability of urban emissions trajectories, atmospheric monitoring of greenhouse gases (GHG) has been deployed over several metropolitan areas. This approach offers an independent and transparent solution to measuring urban emissions. However, careful design of the monitoring network is crucial to be able to monitor the most important sectors as well as to adjust to rapidly changing urban landscapes.

We present here a joint study of Paris and Munich emissions trajectories to demonstrate how climate action plans, carbon emission inventories, and urban development plans can be combined to construct high-resolution projected emissions maps and to help design optimal atmospheric monitoring networks. We show that these two European cities will encounter widely different GHG emission trajectories in space and time, reflecting different emission reduction strategies and different constraints due to administrative boundaries. The projected CO₂ emissions for the milestone years 2030 and 2050 are based on the 2019 spatially distributed 1km x 1km TNO inventory. Future emissions scenarios are based on the analysis of their respective Climate Action Plan. Individual mitigation measures are quantified, sectorized and the resulting saving potentials are applied to the 2019 TNO inventory, used as baseline. The projected CO₂ emissions rely on future actions, hence uncertain, but we demonstrate how emission reductions vary significantly at the sub-city level. 

We show here how climate actions, population growth, and urbanization plans produce mixed spatial patterns across both cities. We conclude that quantified individual cities’ climate actions are essential for strengthening climate policies and their effectiveness at the city scale. Harmonization and compatibility of climate plans from various cities are necessary to make intercity comparisons of climate targets possible. In terms of atmospheric monitoring, our results demonstrate the need for additional measurement stations located inside the densest areas of the two cities but also in the cities’ outskirts to track local positive and negative emission trends over the coming decades.