Global warming caused changes in precipitation in the Fertile Crescent and its relationship to changes in the Zagros Mountain generated barrier jet.

Regional climate model runs were performed over the Middle East for both present day and future climate conditions under the IPCC SRES A2 emissions scenario. Precipitation events in the Fertile Crescent were placed into four classes using the ISODATA clustering algorithm based on water vapor fluxes into the region. One of these classes is characterized by a strong southerly flux caused by the formation of a barrier jet on the Western slopes of the Zagros Mountains. This event class produces the largest precipitation events, such that while only 10.5% of events fall into this class, they account for ~18.5% of precipitation early in the 21st century. By the end of the 21st century these barrier jet associated events are both larger and more numerous, representing 23% of events and over 50% of the total precipitation.