Quelles expériences et quelles représentations pour construire le lien entre CO₂ et réchauffement climatique avec des non spécialistes?

This article proposes a logic of construction of the link between the increase in CO₂ concentration in the atmosphere and global warming. Establishing this link provides an initial qualitative argument for understanding the human origin of climate change, prior to understanding the climate models used to establish this knowledge. The central aim of this approach is to make it accessible with a minimum of conceptual prerequisites, so that it can be used with non-specialists, particularly in the context of science teaching in the final year of general education (in France). This proposal is based on a joint analysis of the physical content, existing teaching approaches and the difficulties experienced by students. The logic developed implies first of all a construction of the notion of infrared radiation, in order to be able to interpret pictures of CO² and air balloons observed with an infrared camera. By extrapolating these observations to the Earth system, it is possible to understand the effect of adding CO² to its radiation balance. We argued that this explanation, at this level, can only be rigorously carried out with a radiation balance restricted to exchanges between the Earth system and Space (without considering those with the atmosphere).