Since the end of the last glacial (ice age) 12,000 years ago, humans have lived in an interglacial period of relatively warm climate called the Holocene. Compared to the highly variable climate that is encountered during glacials, the Holocene was relatively stable.

First civilizations

Most intriguingly, the transition from the stone age to the modern industrial age has entirely taken place during this brief period of stable climate which made reliable agricultural food production available. People started to settle down and give up their former lives as hunters and gatherers. Evidence for a first permanent settlement (the first “city”) in Jericho dates back to 11,000 years ago. The Egyptian and Babylonian civilizations showed up about 5,000 and 4,000 years ago, respectively.

Holocene climate

Although climatic variations during the Holocene have been small compared to those occurring during glacials, they have not been insignificant. E.g. great parts of the Saharan desert, which are now hyper-arid, were covered by vegetation in the early Holocene. Moreover, the level of north-African lakes stood much higher then.

Influence of climate variability on civilizations

Climatic variations during the Holocene have strongly affected human societies. By comparing historic evidence to knowledge about past climatic variations it was found that the collapse of ancient civilizations could sometimes be directly related to climatic variability, especially when a transition towards drier conditions took place. This was observed e.g. for the decline of the Akkadian Empire (Mesopotamia, Cullen et al. (2000)) around 2170±150 BC and the demise of the Maya empire (northern Central America) after the occurrence of multi-year droughts centered at approximately 810, 860, and 910 A.D. and leading to social stress (Haug et al., 2003).

References

Cullen, H. M., deMenocal, P. B., Hemming, S., Hemming, G., Brown, F. H., Guilderson, T., and Sirocko, F., 2000. Climate change and the collapse of the Akkadian empire: Evidence from the deep sea. Geology, 28(4), 379–382.

Haug, G. H., Gunther, D., Peterson, L. C., Sigman, D. M., Hughen, K. A., and Aeschlimann, B., 2003. Climate and the collapse of Maya civilization. Science, 299(5613), 1731–1735.