A few prospective ideas on climate reconstruction: from a statistical single proxy approach towards a multi-proxy and dynamical approach
1CEREGE, CNRS/Aix-Marseille Université UMR6635, BP 80, 13 545 Aix-en-Provence cedex, France
2ECCOREV, CNRS/Aix-Marseille Université FR3098, BP 80, 13 545 Aix-en-Provence cedex, France
3Institut des Sciences de l'Environnement, UQAM, Montréal PQ, H3C 3P8, Canada
4LSCE, CNRS/CEA UMR1572, Domaine du CNRS, 91 198 Gif-sur-Yvette, France
5CNRS, UMR6249, Laboratoire Chrono-Environnemment, UFR des Sciences et Techniques, 16 Route de Gray, 25 030 Besanon, France
Abstract. Important progresses in palaeoclimatological studies have been made using statistical methods. But they are in somewhere limited as they take the present as an absolute reference. The availability of mechanistic models to simulate the proxies measured in the sediment cores gives now the possibility to relax this constraint. In particular, vegetation models provide outputs comparable to pollen data. We present the evolution of the mechanistic approach based on model inversion with several examples where models are progressively more sophisticated (from an equilibrium BIOME3 model to a dynamic LPJ-GUESS model). We show also how it is possible to take into account several proxies measured on the same core (lake-level status and δ13C) when they are related to a component of the vegetation. Examples presented concern Last Glacial Maximum in Europe and Africa, Holocene in a site of the Swiss Jura, an Eemian site in France. The main results are that: (1) pollen alone is not able to provide exhaustive information on precipitation, (2) assuming past CO2 equivalent to modern one may induce biases in climate reconstruction, (3) vegetation models seem to be too much constrained by temperature relative to precipitation in temperate regions.