A comparison of ten different published reconstructions of mean temperature changes during the 2nd millennium. More recent reconstructions are plotted in redder colors, older reconstructions appear in bluer colors. An instrumental history of temperature is also shown in black. The medieval warm period and little ice age are labeled at roughly the times when they are historically believed to occur, though it is still disputed whether these were truly global or only regional events.

The 2013 report by the Intergovernmental Panel of Climate Change (IPCC) and a summary of the huge volume can be found here. It is possible that the rise and fall of huge empires during the past thousand or two thousand years coincided with climate change. Juan Cole has related the decline of the Safavid and Mughal empires in the late 17th and early 18th centuries to the Maunder Minimum of solar activity between 1645 and 1715 CE leading to a period with low temperature. The Maunder Minimum coincides  with what is known as the “Little Ice Age” which in turn saw the Thirty Years’ War in Europe (1618-1648).

A couple of centuries before the rather low temperatures in the 17th and 18th centuries, world enjoyed what is called the “Medieval Warm Period” around 900-1200 CE. It saw the rise of some of the largest empires in history, in particular the Mongolian Empire. A theory tells that their most eminent (and cruel) Emperor Chengis Khan (d. 1227) may have reverted the trend and successfully scrubbed 700 million tonnes of carbon dioxide from the atmosphere. The world’s greenest conqueror ever. During the Mongolian invasions in the 13th and 14th centuries he, his successors and their hordes conquered an incredible 22% of the world’s total land area and possibly killed 40 million people. One significant side effect may have been widespread reforestation of depopulated areas which led to more carbon absorbed from the atmosphere.

Research done by Julia Pongratz of the Carnegie Institution for Science’s Department of Global Ecology indicates that “humans started to influence the environment thousands of years ago by changing the vegetation cover of the Earth’s landscapes when we cleared forests for agriculture.” Long-lasting invasions and carnage such as the Mongolian and the conquest and depopulation of the Americas (1519-1700) may in fact have had a dampening impact on man-made carbon dioxide emission and a strong effect on regrowth of forests, short-lived plague outbreaks in Europe (the Black Death in 1347-1400) and the Fall of the Ming Dynasty in China (1600-1650) had probably not.

The Mongolian invasions which probably have been sparked by so far unexplained climate change (higher temperatures and extensive rain fall in Mongolia might have led to more favorable living conditions in vast areas of East Asia and Eurasia) were preceded by another huge empire, that of the Great Seljuqs (1037-1134). This dynasty of steppe nomads, which trace their origin to Seljuq (d. 1038)  who served in the Khazar army before he converted to Islam, defeated the Byzantines at Manzikert in Anatolia in 1071, fought the Crusaders, and is generally considered responsible for the Sunni Revival of the 11th and 12th centuries. Under their governance Iran saw its first, in a long series, climax of culture after the Arab conquest in the 7th century. Has it been climate change (the “Medieval Warm Period”) forcing them to seek new pastures in the Iranian plateau and Anatolian highlands?

Where are we escaping after Earth has become inhabitable? Terraformed planets?

28 September 2013 @ 9:56 am.

Last modified December 29, 2014.