For the first time, independent scientific monitoring data from ICOS Cities – an EU-project coordinated by ICOS – can confirm mitigation progress in Paris and show significant reduction in greenhouse gas (GHG) emissions. These results open the way for an efficient science-based support to policymaking in Europe. A new European survey also shows that Parisian residents expect the city authorities to live up to their climate concerns and act.
While the public Airparif (the independent air quality observatory in the Paris region) Emissions Inventory shows a significant decrease by 26% in CO2 emissions for Paris between 2015 and 2022, this result has now been independently verified thanks to a major collaborative European effort, the ICOS Cities project, that deployed the largest urban CO2 sensor network ever in Europe. The new continuous atmospheric monitoring data confirm that greenhouse gas emissions have indeed decreased by approximately 25% in the city, aligning almost perfectly with the reported inventory figures.
“We never got to this point before. Most inversion studies elsewhere in the world have shown a disagreement with current emission inventories by 20 to 30% on average. On top of it, we confirmed our findings with local flux data across Paris,” says Professor Thomas Lauvaux, Laboratory for Climate and Environmental Sciences (LSCE) and University of Reims (URCA).
The successful alignment of the independent atmospheric data with the official inventory, based on socio-economic data, marks a significant step forward in climate science and policy validation – not only for Paris but also for other cities in France and Europe.
“This collaboration validates our inventory methods while demonstrating the potential to improve the spatial accuracy and timeliness of our CO2 emissions knowledge. It also shows the capacity to provide a new kind of independent emissions data in other cities, without having a reliable emissions inventory, like the one provided for Paris by Airparif,” says Karine Léger, Director at Airparif.
Empowering policymakers for targeted climate action
The urban CO2 sensor network in Paris was set up and operated by LSCE (CEA-CNRS-UVSQ) in 2022-2025 as part of the Europe-wide ICOS Cities project, developing pioneering observations of GHG emissions in urban areas. When combining the new real-time observational data with the emissions inventories, the city authorities get a complete, timely and accurate picture of urban emissions and a reliable foundation for designing targeted climate action.
"The atmospheric monitoring system is almost like having an accountant that goes line by line to verify the totals. The atmosphere can’t lie – it sees the sum of all the emissions, mixed together," says Professor Lauvaux.
More efforts needed for Paris to become carbon-neutral by 2050
While the data validates the city's overall progress, another scope of the ICOS Cities project has been to evaluate the region’s race to decarbonise. If the Paris climate action plan is fully implemented, the city should be on track to meet its 2030 climate target.
“However, the current policy package falls short of the city’s 2050 net zero goal,” says Dr Ivonne Albarus, IPCC, one of the scientists behind the study.
The findings also reveal a critical socio-economic dimension of climate action, with significant differences in how emissions are being reduced across the Paris metropolitan area, between the urban core and the suburbs. The challenge for the city is now to balance climate action and social justice, while scaling up its ambitions beyond the current trajectory to ensure both 2030 and 2050 net-zero goals will be achieved, according to Dr Albarus.