Deliverable D6a: Regional climatic characteristics for the European sites at specific times: the dynamical downscaling. Work Package 2, Simulation of the future evolution of the biosphere system using the hierarchical strategy. Modelling Sequential Biosphere Systems under Climate Change for Radioactive Waste Disposal (BIOCLIM)

The overall aim of BIOCLIM is to assess the possible long-term impacts due to climate change on the safety of radioactive waste repositories in deep formations. This aim is addressed through the following specific objectives: • Development of practical and innovative strategies for representing sequential climatic changes to the geosphere-biosphere system for existing sites over central Europe, addressing the timescale of one million years, which is relevant to the geological disposal of radioactive waste. • Exploration and evaluation of the potential effects of climate change on the nature of the biosphere systems used to assess the environmental impact. • Dissemination of information on the new methodologies and the results obtained from the project among the international waste management community for use in performance assessments of potential or planned radioactive waste repositories. The BIOCLIM project is designed to advance the state-of-the-art of biosphere modelling for use in Performance Assessments. Therefore, two strategies are developed for representing sequential climatic changes to geosphere-biosphere systems. The hierarchical strategy successively uses a hierarchy of climate models. These models vary from simple 2-D models, which simulate interactions between a few aspects of the Earth system at a rough surface resolution, through General Circulation Model (GCM) and vegetation model, which simulate in great detail the dynamics and physics of the atmosphere, ocean and biosphere, to regional models, which focus on the European regions and sites of interest. Moreover, rule-based and statistical downscaling procedures are also considered. Comparisons are provided in terms of climate and vegetation cover at the selected times and for the study regions. The integrated strategy consists of using integrated climate models, representing all the physical mechanisms important for long-term continuous climate variations, to simulate the climate evolution over many millennia. These results are then interpreted in terms of regional climatic changes using rule-based and statistical downscaling approaches. This deliverable, D6a, focuses on the hierarchical strategy, and in particular the MAR simulations. According to the hierarchical strategy developed in the BIOCLIM project to predict future climate, six BIOCLIM experiments were run with the MAR model. In addition to these experiments a baseline experiment, presenting the present-day climate simulated by MAR, was also undertaken. In the first step of the hierarchical strategy the LLN 2-D NH climate model simulated the gross features of the climate of the next 1 Myr [Ref.1]. Six snapshot experiments were selected from these results. In a second step a GCM and a biosphere model were used to simulate in more detail the climate of the selected time periods. These simulations were performed on a global scale [Ref.1]. The third step of the procedure is to derive the regional features of the climate at the same time periods. Therefore the results of the GCM are used as boundary conditions to force the regional climate model (MAR) for the six selected periods and the baseline simulation. The control simulation (baseline) corresponds to the regional climate simulated under present-day conditions, both insolation forcing and atmospheric CO2 concentration. All the BIOCLIM simulations are compared to that baseline simulation. In addition, other comparisons will also be presented. Tableau 1 summarises the characteristics of these BIOCLIM experiments already presented in [Ref.1] and [Ref.2].