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In this contribution, some of the issues related to the workings of climate models are discussed. The hierarchy of available models is mentioned, and examples are given of both the simplest process models and of state-of-the-art global climate models. The concepts of climate scenarios and climate predictability are discussed, and the methods for validating climate models are mentioned. Some of the many open questions in climate modelling are explored, focussing in particular on the issue of scale interaction: on the one hand, the need for downscaling the large-scale climate information for impact studies, using regional climate models and statistical/stochastic downscaling procedures; on the other hand, the need for upscaling the small-scale dynamics associated with surface processes to quantify their effects on regional and global climate. The general theme of the parameterization of unresolved, sub-grid scale processes such as turbulent convection is also mentioned. The specific example of climate-biosphere interaction is considered in some detail, with specific attention to the issue of climate-vegetation interaction in arid and semi-arid regions and the role of vegetation in determining albedo and moisture fluxes. The need for a deeper understanding of the fundamentals of climate dynamics is finally advocated.