Paris has reduced its greenhouse gas emissions by a quarter in ten years, according to a study

This new data was collected through the unprecedented deployment of a network of atmospheric sensors via the European consortium ICOS Cities, intended to guide cities in their policies to reduce air pollution.

Around thirty carbon dioxide (CO2, the main greenhouse gas emitted by cities) sensors have been installed at different heights on the roofs, antennas and towers of Paris and Ile-de-France.

They measured in real time a decrease of about 25% in the concentrations and flows of greenhouse gas emissions in the capital between 2015 and 2025, or "a little more than one megaton of CO2", Professor Thomas Lauvaux of the Laboratory for Climate and Environmental Sciences (LSCE), who orchestrated the deployment of the sensors under the leadership of ICOS, explained to AFP.

"For a city like Paris, this is enormous. It's as if we had removed the equivalent of 200.000 inhabitants from the map, even though human activity has increased," the researcher added.

Main factors in the decline: the decrease in the share of internal combustion engine vehicles and the energy renovation of buildings.

These results confirm the estimates of Airparif, the air quality observatory in the Paris region, which are based on an inventory of emission-generating activities (wood heating, traffic, industry, etc.) the latest of which dates from 2022.

"Our data is almost perfectly aligned with that of Airparif," which is time-consuming to collect and often incomplete, Professor Lauvaux stated at a press conference. By supplementing its inventory with sensor measurements, which allow for mapping emissions, the Île-de-France observatory will be able to better assess public policies aimed at improving air quality.

The survey reveals, for example, that the potential for reducing emissions is highest in the eastern part of the Paris metropolitan area, given the quantity of energy-inefficient housing.

If the capital fully implements its climate action plan, "it should be on track to achieve its 2030 climate target" under the 2015 Paris Agreement, whose most ambitious goal is to limit global warming to +1,5°C compared to the pre-industrial era, the study authors suggest.

But the current package of measures "does not allow the city to achieve its goal of carbon neutrality by 2050," according to Ivonne Albarus, a scientist with the Intergovernmental Panel on Climate Change (IPCC).