Raincheck: A new diachronic series of rainfall maps for Southwest Asia over the Holocene

Abstract

Fluctuations in climate have been associated with significant societal changes, both in the modern day and in the past. In dryland environments such as much of Southwest Asia, rainfall is often used as a proxy for soil moisture available for crop production, and in pre-industrial societies this is assumed to directly relate to food production capacity and security. However, rainfall values are commonly quoted in archaeological literature without further context. Variability between values arising from different methods and timescales are rarely considered. This is important as small changes in rainfall can have profound effects on the interpretation of sites and landscapes. Here, we present a novel set of snapshot precipitation maps for Southwest Asia between the years 10,240 BP and 300 BP, based on previously published natural archive data by Bar-Matthews and Ayalon (2004) from Soreq Cave, and a newly derived modern rainfall map. The modern map was created using station data from the years 1960–1990 and a geostatistical interpolation technique applied across 14 separate zones. We outline the steps involved in the creation of the maps and provide access to, and clear explanations of, the data and methods used. Using the hindcasted maps, two case studies to highlight why a nuanced approach to rainfall is required in the study of ancient societies are examined. Changes to the spatial extent of the so-called ‘Zone of Uncertainty’ through time, as well as land suitable for rainfed agriculture throughout time using a simple model are calculated. It is demonstrated that relatively small fluctuations in rainfall can have a significant impact on the distribution of moisture availability for the region. It is argued that archaeologists need to be aware of the sources and limitations of the rainfall data used in their interpretations, and our map series is offered as a baseline dataset.