Session: Invited talks
Author: Martin Claussen / email@example.com / Max Planck Institute for Meteorology and Universität Hamburg
Palaeoclimatic theory and modelling seem to converge in the interpretation of archaeological and geological evidence of the Sahara and Arabian deserts being much greener than today during the early and mid-Holocene. Currently it is understood that the change in the Sahara and Arabian deserts was triggered by changes in insolation due to steady variations in the Earth orbit. The climate and ecosystem response to insolation changes was amplified by feedbacks between atmosphere, ocean and land. The atmosphere - land feedbacks include changes in vegetation cover, vegetation composition, lake coverage, soils and emission of mineral dust. Depending on the specific biases and the different complexity of models, some models match data better than others. Hence, it is not yet possible to quantify the efficiency of the various feedbacks involved. Likewise, the interpretation of local data is limited given the coarse spatial resolution of current climate models. The situation becomes even more challenging when addressing the question of the termination of the African Humid Period. And even if model and data converge, then it might be attributed just to a successful tuning of model parameters. Some important processes like the dynamics in plant diversity or the large uptake of mineral dust by small-scale intense convective systems are not adequately represented by current climate system models. In conclusion, we might have available most, if not all, ingredients for making the Holocene Sahara greener than today, but the precise recipe is still missing.