The greening of Arabia: multiple opportunities for human occupation of the Arabian peninsula during the Late Pleistocene inferred from an ensemble of climate model simulations

Climate models are potentially useful tools for addressing human dispersals and demographic change. The Arabian Peninsula is becoming increasingly significant in the story of human dispersals out of Africa during the Late Pleistocene. Although characterised largely by arid environments today, emerging climate records indicate that the peninsula was wetter many times in the past, suggesting that the region may have been inhabited considerably more than hitherto thought. Explaining the origins and spatial distribution of increased rainfall is challenging because palaeoenvironmental research in the region is in an early developmental stage. We address environmental oscillations by assembling and analysing an ensemble of five global climate models (CCSM3, COSMOS, HadCM3, KCM, and NorESM). We focus on precipitation, as the variable is key for the development of lakes, rivers and savannas. The climate models generated here were compared with published palaeoenvironmental data such as palaeolakes, speleothems and alluvial fan records as a means of validation. All five models showed, to varying degrees, that the Arabia Peninsula was significantly wetter than today during the Last Interglacial (130 ka and 126/125 ka timeslices), and that the main source of increased rainfall was from the North African summer monsoon rather than the Indian Ocean monsoon or from Mediterranean climate patterns. Where available, 104 ka (MIS 5c), 56 ka (early MIS 3) and 21 ka (LGM) timeslices showed rainfall was present but not as extensive as during the Last Interglacial. The results favour the hypothesis that humans potentially moved out of Africa and into Arabia on multiple occasions during pluvial phases of the Late Pleistocene

Floods in Jeddah, Saudi Arabia: Unusual Phenomenon and Huge Losses. What Prognoses

Situated in the South-West of Saudi Arabia, Jeddah is the biggest port city in the red sea and the kingdom's second city after Riadth. Jeddah has a population of 3500000 inhabitants. It benefits from many economic assets due mainly to its being a transit point toward the holly sites of Islam. Despite being characterized by a dry climate, by poor rain fall levels, by deficits of rain compared to evaporation, and by the irregularity of water flow systems along with the functional degradation of its hydraulic networks, Jeddah underwent many unexpected floods- three big ones in 2009, 2010, and 2011. The human tolls as well as the material losses were huge: hundreds dead, thousands of damaged buildings which were built on slopes or close to river beds with legal permits. Such floods were studied by local and national authorities as well as scholars in order find adequate solutions. It is within this framework and with modelization statistics and cartographic analyses in mind that we will attempt to understand what caused such floods: –Natural causes (geo-morphological specifics, climate change, intensive rainfall), –Human causes: lack of hazard culture, urban extension and planification, and the absence of viable strategies of preventio