The archeologist Harvey Weiss and his colleagues working at the Tell Leilan excavation site in Syria have established the occurrence of a global climatic event occurring sometime around 2200 BCE. This cataclysm is now widely believed to be the primary factor responsible for the collapse of the ancient Akkadian empire and the population diaspora which abruptly followed. See "Beyond the younger Dryas: Collapse as adaptation to abrupt climate change in ancient West Asia and the Eastern Mediterranean" for an influence diagram model we developed for the Akkadian pre-collapse economy.