A greenhouse gas monitoring network was set up around Paris. From July 2022 to December 2024, three stations placed along the main wind direction detected differences of 0.5–1 ppm between sites. Compared with WRF-Chem (Weather Research and Forecasting model coupled with Chemistry) simulations using the Origins.earth inventory, the data suggest that emissions are overestimated by the inventory. A reduction of about 34 % would be needed, a stronger correction than indicated by surface-based studies.