Solar Influence on Medieval Megadroughts in the Greater Near East

Abstract:

Recent surveys of medieval era chronicles provide calendar accurate information of years of unusual, extreme weather and climate events in areas surrounding the eastern Mediterranean, between the mid-A.D. 10th century and end of the 11th century. Put together, these documents show that the region was simultaneously afflicted by unprecedented sever and persistent droughts in Egypt's Nile Valley and by unusually cold and dry winters associated with crop failure and loss of pasture areas in present-day Iraq and Iran, and in historical Khurasan. We show that this documentary information is consistent with the annually dated Nile summer flood record as measured at the Cairo Nilometer site and within acceptable dating accuracies with much more coarsely resolved regional paleoclimate proxies. We furthermore note that the timing of these events coincided with the Oort Grand Solar Minimum that reached its peak between A.D. 1040 and 1080. Given the scientific evidence for the impact of solar minima on sea surface temperatures in the equatorial Pacific and how the latter affect the intensity of the African summer monsoon, we argue that the Oort Solar Minimum forced the frequent failure of the Nile summer floods resulting in dearth and famine in Egypt. Furthermore, the simultaneous cold and dry winters in the northern Near East are also consistent with the hypothesized solar minimum influence on the North Atlantic Oscillation and on the intensity of the Siberian High. This interpretation underscores the sensitivity of the climate system to variations in solar irradiance, particularly on multi-decadal time scales, to their role in regional processes, and their impact on human history and may help understand other rapid Mediterranean cooling events that occured during the Holocene.