Empirical comparisons between the past 5000 years of European and eastern Mediterranean history and precipitation as recorded by ice accumulation in the GISP2 (Greenland) ice core

Abstract

Adequate and regular levels of precipitation are fundamental to the sustained success of civilizations based on early agricultural production technologies, but palaeoclimate studies have concentrated on temperature. Potentially important insights into the fates of early civilization can be gained, however, from long term records of precipitation. Patterns in precipitation over the past 5000 years recorded by the ice accumulation balance in the GISP 2 ice core on the Greenland plateau appear to be correlated with major events in European and Mediterranean history. Near Greenland, Viking raids coincided with a major step-wise precipitation increase after 600 CE. Viking settlement of Greenland coincided with a precipitation low. During the Egyptian Old Kingdom period of pyramid-building precipitation was higher than when the New Kingdom tombs were excavated. The Old Kingdom and Akkadian Empire both failed as precipitation descended into the same prolonged precipitation low. The end of the New Kingdom and of the other Bronze Age civilizations in the eastern Mediterranean and around the Aegean Sea coincided with the lowest ice accumulation rate in the past 5000 years. The Roman “Imperial Good Times” coincided with a precipitation high. The brief 2nd century imperial reigns and those of late New Kingdom pharaohs accompanied precipitation lows, as did the Antonine and Justinianic plagues. A trans-Alpine “production see-saw” hypothesis, in which the same precipitation levels generated opposite effects, fits the sequence of successes and failures of western civilizations. Global warming captures the headlines and occupies global research programmes, but precipitation is a key factor in food production now and even more so in the past. Until recently the margin between seed harvested and seed sown was very low: drought or floods could eliminate it entirely. Most climate studies relating to the past 5,000 years in Europe and the Mediterranean are local in scope. There is no overall pattern against which to interpret regional historic events. Ice accumulation (balance between precipitation and evaporation) through time on the Greenland plateau may provide an overarching perspective on the precipitation history of these areas. Preliminary comparisons of the well-dated ice accumulation record with dates of significant historical events such as the collapse of Bronze Age civilizations, the Viking diaspora, and pandemics suggest that the events were correlated with lows and highs of Greenland ice accumulation. An “Alpine see-saw” model may be useful in understanding why changes in the fortunes of communities north and south of the mountains were often in opposition. Finally, events can be correlated without one causing the other. The examples canvassed here meet accepted criteria for their being a causal relationship between precipitation and the fates of civilizations.