Selected by the French National Research Agency (ANR), the Chair is backed by the University of Versailles Saint-Quentin-en-Yvelines and co-funded by SUEZ, Thales Alenia Space and Total. Interview with Philippe Ciais, Chair Coordinator at the Climate and Environment Science Laboratory (LSCE, CEA/CNRS/UVSQ) and a member of the IPCC for the previous reports on climate change.
You have been working on the carbon cycle and greenhouse gases (GHG) for many years. Can you explain the interactions between air pollution and climate warming?
The main thing that air pollution and climate change have in common is their anthropic origin. The use of fossil fuels in transport and industry produces pollutants that degrade air quality and GHGs that affect the climate. The main GHGs whose increased concentration leads to climate change are carbon dioxide (CO2) (combustion of fossil fuels and deforestation), methane (CH4) (activities associated with agriculture, the decomposition of organic waste and the oil and gas sectors) and nitrous oxide (N2O) (nitrogen fertilisers used in agriculture and industry).
The important thing to remember is that the interactions between air quality and climate change are very complex. For example, climate change affects air quality by influencing meteorology. This is the case with heatwaves, which lead to the formation of ozone pollution (O3), favoured by sunshine and high temperatures. These interactions between climate and air quality depend on the nature of the pollutants in the air. On one hand, emissions of black carbon particles warm the climate by absorbing infrared radiation. On the other, nitrogen oxide and sulphur oxide tend to cool the climate, because the aerosols formed from these compounds block solar radiation. In addition, volatile organic compounds (VOCs) are pollutants with an indirect effect on the climate, as they contribute to the formation of ozone pollution, a GHG that warms the climate.
It is still difficult to measure and monitor GHG emissions across the planet. How do you explain this complexity?
The three main GHGs (methane or CH4, nitrous oxide or N2O and carbon dioxide or CO2) are relatively inert and thus well mixed in the atmosphere, compared to pollutants (fine particles, black carbon, aerosols of NOx and SO2, VOCs, CO and O3), which are quickly destroyed in the atmosphere the further you move from their sources. When measuring the atmospheric concentrations of GHGs, it is possible to track the origins of the emissions as long as the measurements are precise and deployed near their sources, such as cities or industrial sites. With these GHG measurements near emission sources, we use atmospheric dispersion models to deduce the quantities emitted.
You coordinate the TRACE Industrial Chair. Can you present its objectives?
The goal of the programme, run in collaboration with SUEZ, Total and Thales Alenia Space, is to conduct applied research to enable significant progress in measuring GHG emissions, including CO2 and CH4. For industrial sites, we are testing and optimising low-cost sensors that can be placed in a network around emission zones. For example, with Origins.Earth we are building a network of measurements of CO2 emissions in Paris that will allow us to track reductions in emissions over time and exploit them in the voluntary carbon credits market.
At the same time, we are conducting "life-sized" experiments on the ground to measure emissions from working waste treatment and recovery units. We also release natural gas (mostly methane) under controlled conditions at an industrial space fitted with sensors in order to refine and calibrate our atmospheric dispersion models, which are then used to monitor emissions. Ultimately, these experiments will offer two benefits to the operators of industrial sites: installing solutions to detect and reduce leaks of CH4 in order to fight climate change and improving the management of each site.
How is the collaboration between universities and industrial partners organised?
Our laboratory carries out the TRACE research work alongside industry and the National Research Agency. Our partnership with SUEZ gives us easier access to industrial sites, including waste treatment and recovery units. The cooperation also involves exchanging information in order to share a global vision of the site management and the data that are essential to link our results to operations at each site.
Over the last 18 months, we have been monitoring the progress of our investigations every month with a monthly presentation of our results. These constitute vital data that will ultimately enable us to develop the most precise emissions measurement tool possible.
Learn more about the TRACE program on the dedicated website.