Résumé
During the 10 millennia of the Neolithic and Metal Ages, the Mediterranean islands were characterized by intermittent phases of settlement and abandonment by farmer communities, particularly on small islands. More frequent and longer than on the continents, archaeologists refer to a theory of island abandonment. The causes of these island abandonments, whether concomitant or not, are a matter of debate within the community of prehistorians and historians; some are linked primarily to historical events (conflict, raids, insecurity, epidemics, etc.), others to environmental factors including climatic fluctuations with alternating Decadal or multi-decadal Dry or Wet Periods (DDWP) on a local or regional scale. In many cases, a combination of historical and environmental factors seems likely. The aim is to simulate fluctuations in annual precipitation over the several millennia under consideration, by calibrating the Interannual Variability of Precipitation (IAVP) observed at 25 meteorological stations located along a transect of Mediterranean islands: (Cyprus, Rhodes, Crete, Malta, Sicily, Sardinia and the Balearic Islands) on top of other stations along the continental coastlines. Larger-scale climatic variations of secular or millennial duration will not be taken into account, and only the erratic nature of annual rainfall totals in the Mediterranean regime will be considered, including during the historical period under consideration. Analysis of the IAVP at current weather stations with long rainfall series shows that they are homogeneous throughout the region (±21%), with the exception of the Adriatic (±18%), making it possible to define a stationary regional IAVP model.Based on this observation, a Stochastic Generator (SG) incorporating this property of the Mediterranean IAVP is used to create "memory-free" random annual precipitation chronicles over several thousand years. The GS runs provide a sampling of annual rainfall scenarios, enabling us to identify the Intensity, Duration and Frequency (IDF) characteristics of DDWPs.The SG simulations (or "runs") suggest that the IDFs of the DDWPs must have impacted several generations of farmers over the 10,000-year period under consideration, leading to the ultima ratio of island abandonment, depending on the island configuration. The dilemma of "should I stay or should I go?" is all the more important in an island environment, since it implies migration by boat, on top of complete abandonment of the land and a prospect of resettlement that is far more difficult than in continental regions.It is likely that this constant confrontation with rainfall hazards led to the gradual development of a culture of risk, or more precisely, a "culture of hazard" in the intergenerational memory of farming communities over the long period of Neolithic evolution, particularly in the constrained and hydrologically fragile space of small islands. In his book “Homo domesticus”, James Scott defines the prehistoric Neolithic period as a "running period" lasting several millennia before the appearance of the first states during the Metal Age, the anthropologist specifying that several hundred generations of farmers were involved. This research on the Mediterranean IAVP properties for the purpose of "postdiction" of the past climate is part of an approach that could be defined as "experimental geohistory", with the present shedding light on the past. They can also help to clarify the debate with climate sceptics, as they show how multidecadal rainfall variations must be clearly distinguished from the ongoing phenomenon of Climate Change (CC).