Set up a greenhouse gas emission inventory

The inventory is essential to define reduction targets, to pinpoint emission sources, to design effective policies, and to track overall progress. This service offers practical, flexible guidance to build reliable inventories using multiple levels and types of data.
 

Inventory basics: Scopes and spatial detail

An emission inventory is an accounting system, based on statistical data, of all greenhouse gas emissions produced by a city over a specific period, typically one year. It provides both a city-wide overview and, when spatially and temporally distributed, insights into local hotspots and daily or seasonal variations such as rush-hour peaks.

For robust accounting, emissions are categorised by scope:

• Scope 1 (Direct): Emissions physically produced within the city boundary (e.g., combustion of natural gas for heating, fuel from vehicles).
   
• Scope 2 (Purchased): Indirect emissions from purchased energy (e.g., electricity, district heating/cooling).
   
• Scope 3 (Other Indirect): All other emissions resulting from activities that occur outside the city boundary (e.g., waste, food production and transport to the city, air travel).

During ICOS Cities, the Inventory+ concept has been developed. It describes the highest possible quality of inventories that can be provided for cities. The strength lies in the dense interaction between inventories and observations, further developing inventories and providing services for their improvement. Consequently, ICOS Cities emphasises the need for spatial disaggregation – breaking down total emissions by sector, location, and time to use observations to verify and improve inventories. Traditional inventories often provide only city-wide totals. We recommend a minimum spatial resolution of 100x100 meters to identify local hotspots and assess neighbourhood-level policy impacts.

 

Step-by-step: Creating emission inventories

This service defines goals and requirements for processing emission data. It is designed to be accessible even for cities with little prior experience. Cities with more capacity can also include additional local data, improving accuracy and level of detail.
 

1. Downscaling tool:

The ICOS Cities downscaling tool provides a rapid, first reasonable estimate of city-wide emissions for the 15 cities in the ICOS Cities network, but all European cities can make use of this tool. This tool uses existing high-level European inventory data (e.g., national reporting to UNFCCC) and redistributes them over the city domain using open-access spatial proxy data (e.g., population density, road networks, building footprints). This minimises the initial burden of local data collection.

2. Targeted bottom-up inventories:

Once hotspots are identified via downscaling, cities can focus efforts on developing detailed bottom-up inventories for priority sectors. This involves gathering local, sector-specific data (e.g., detailed energy consumption by building type, specific traffic counts) for maximum accuracy where it matters most. Compiling comprehensive emission data requires significant resources and specialized knowledge. Thus, the downscaling tool can offer guidance on data collection strategies, emphasising that local or city-specific data are preferred for higher accuracy.

3. Validation and refinement:

Comparing estimates from different approaches (downscaling vs. bottom-up) and, critically, comparing them with atmospheric observation data (Service 4) helps verify accuracy, identify discrepancies, and see where local knowledge adds the most value.

Dive Deeper

Super, I., Denier van der Gon, H., Dröge, R., Schoenmakers, E., Kühbacher, D., Aigner, P., Chen, J., 2025. Guidelines for European cities: a flexible and efficient approach for creating city emission inventories. ICOS ERIC - Carbon Portal. https://doi.org/10.18160/NK88-49TY

Super, I., Denier van der Gon, H.A.C., and Dröge, R.: Downscaling tool to construct city emission inventories, TNO, Utrecht, Netherlands, TNO 2025 R12516, 2025. Guidelines for European cities https://resolver.tno.nl/uuid:8b029fed-7721-481b-ba97-6fe2998981ee

Dröge, R., Denier van der Gon, H., Perrussel, O., David, L., Aigner, P., Kühbacher, D., Chen, J., Hinderer, J., Brunner, D., Constantin, L., 2024. Final version of high-resolution city emission inventory for GHGs and co emitted species for 2018, 2020 and 2022. ICOS ERIC - Carbon Portal. https://doi.org/10.18160/0GEF-R5XX

Aigner, P., Kühbacher, D., Chen, J., Althammer, T., Denier van der Gon, H., Hinderer, J., Suhendra, M., Super, I., Yirtar, B., 2025. Temporal Activity Profiles for the City of Munich (2019-2024). https://doi.org/10.18160/Z2CB-JKQ2

Kühbacher, D., Aigner, P., Chen, J., Hinderer, J., Super, I., Denier van der Gon, H., Dröge, R., Schoenmakers, E., Hohenberger, T., 2025. Gridded anthropogenic emissions of CO₂, CH₄ and co-emitted pollutants for the city of Munich for the period 2019-2024. https://doi.org/10.18160/2K5S-967C

Kugler, T., Hörger, C., Constantin, L., Brunner, D., 2025. Gridded anthropogenic emissions of CO₂ and other greenhouse gases and air pollutants for the city of Zurich in 2022. https://doi.org/10.18160/2H6N-Q04Z

Lian, J., Lauvaux, T., Utard, H., Bréon, F.-M., Broquet, G., Ramonet, M., Laurent, O., Albarus, I., Chariot, M., Kotthaus, S., Haeffelin, M., Sanchez, O., Perrussel, O., Denier van der Gon, H. A., Dellaert, S. N. C., and Ciais, P.: Can we use atmospheric CO₂ measurements to verify emission trends reported by cities? Lessons from a 6-year atmospheric inversion over Paris, Atmos. Chem. Phys., 23, 8823–8835, https://doi.org/10.5194/acp-23-8823-2023 , 2023.