Friday, July 06, 2007

Has solar variability caused climate change that affected human culture?
If solar variability affects human culture it most likely does so by changing the climate in which the culture operates. Variations in the solar radiative input to the Earth’s atmosphere have often been suggested as a cause of such climate change on time scales from decades to tens of millennia. In the last 20 years there has been enormous progress in our knowledge of the many fields of research that impinge on this problem; the history of the solar output, the effect of solar variability on the Earth’s mean climate and its regional patterns, the history of the Earth’s climate and the history of mankind and human culture. This new knowledge encourages revisiting the question asked in the title of this talk.

Several important historical events have been reliably related to climate change including the Little Ice Age in northern Europe and the collapse of the Classical Mayan civilization in the 9th century AD. In the first section of this paper we discus these historical events and review the evidence that they were caused by changes in the solar output.

Perhaps the most important event in the history of mankind was the development of agricultural societies. This began to occur almost 12,000 years ago when the climate changed from the Pleistocene to the modern climate of the Holocene. In the second section of the paper we will discuss the suggestion (Feynman and Ruzmaikin, 2007) that climate variability was the reason agriculture developed when it did and not before.

See back to this post. The actual paper isn't up yet, so I can't read what that "second section of the paper" actually says. If, in fact, agricultural practices became fixed in populations in both the Old and New worlds at about the same time, perhaps it's more environment-driven than people have generally supposed.