Caption: Paleoscience provides data against which to test the performance of climate models run under past boundary conditions different from those that prevail at the present day. This figure shows a first-stage comparison between model simulations and lake level data for the period 6000 years before present. Attention is focused on the Sahara/Sahel region of Africa. There is quite good agreement between models over this area, but all fail to simulate the strong positive hydrological balance demonstrated by the paleo lake level data. This initial mismatch has led to a fruitful interaction between data and modeling communities out of which is emerging a better understanding of the sensitivity of models, and of the climate systems which they represent, to changes in vegetation, land cover and surface moisture.
Duplessy J-C and J. Overpeck (1994) "The PAGES/ CLIVAR Intersection: Providing the paleolimatic perspective needed to understand climate variability and predictability. PAGES Core Project Office, Bern Switzerland.