The main objective of the CARBO-CONTRÔLE project is to quantify CO2 fluxes on the European scale and carbon stocks and fluxes at the national level.

The scientific strategy adopted is to disaggregate – or downscale – fluxes (>100 km) by inversing atmospheric CO2 readings, and to aggregate – or upscale – national stocks and fluxes using climatic fields and satellite information. To achieve this, we will use numeric codes that will subsequently be validated by observation: (I) the three-dimensional atmospheric transport model TM2 and (II) the STOMATE model of the carbon cycle in soils and vegetation, which integrates a semi-empirical parameterization of the biogeochemical processes in ecosystems. These two codes use supercomputers. They were developed and partly validated for the carbon cycle on a global scale. They will be used in the CARBO-CONTROLE project concerning Europe and France in particular.

The project comprises two complementary subsets: (I) an inversion of the European carbon balance based on readings of atmospheric CO2 concentrations and (II) a simulation of French carbon fluxes and stocks and of their variability.

The inversion of the atmospheric fields will be carried out using a Bayesian method that optimizes CO2 sources and sinks over large regions while minimizing the distance between observed concentrations and the concentrations obtained through the transport model.

Europe will be divided into a number of regions, for which the fluxes will be estimated. The uncertainties attached to this approach (density of the measuring network, errors in the simulation of atmospheric transport) will be quantified. The evaluation of carbon fluxes and stocks with the biogeochemical model will be carried out with the STOMATE model. The fields of boundary conditions of the model (vegetation index, climate, etc.) will be prepared with a resolution of approximately 20 km, after which several simulations will be performed for France. We will also examine the sensitivity of stocks and fluxes in response to the parameters of the model, which will help us estimate the uncertainties of the method. The first one-year phase was financed from the end of 1999 to the end of 2000.

Proposed research activities are as follows:

1. To summarize the knowledge available on atmospheric inversions of CO2 fluxes;
2. To refine the diagnosis of inversions for Europe by increasing the number of regions;
3. To prepare the boundary conditions for the STOMATE model;
4. To run a preliminary simulation with STOMATE for Europe;
5. To launch the measurement campaign for the study on the feasability of checking emission results in Ile-de-France.

Expected results are:

• I. The inverse estimate of European fluxes, including all existing atmospheric readings;
• II. A preliminary set of boundary conditions (satellite, climate) for the computation of fluxes in Europe using the STOMATE model.

The CARBO-CONTROLE project comes as part of a series of research projects from LSCE and its partners (listed below). Although these projects share the same methods regarding modelling, the actions proposed in the CARBO-CONTROLE project are entirely original and receive no complementary funding. The other LSCE research projects include FRAISE (national programme CNRS-INSU: inversion of fluxes for the North Atlantic and Indian Oceans), EUROSIB (EEC project 1999-2001: airborne measurements of CO2 and intensive campaigns in Russia and Siberia) and CSOA-INSU (permanent support for the LSCE atmospheric observatories, in Ireland and New Amsterdam).