Some Perspectives on Societal Impacts of Past Climatic Changes

Abstract

We examine a range of paleoclimatic evidence covering approximately the last 2000 years (the Common Era) to provide plausible environmental scenarios as potential drivers and stressors associated with major societal disruption in different parts of the world. The period studied covers both historical, for which there is documentary evidence of impacts, and prehistorical events, for which impacts are inferred from the archeological record. Drought appears to be the most common high-impact stressor in the historical and prehistorical records. Clearly, the adequacy of water supplies for growing food and for an array of other uses is a thread that weaves its way across time and societies.We also briefly outline some of the key physical mechanisms leading to climatic changes of a magnitude that could have led to societal disruptions. These include solar variability and large explosive volcanic eruptions, both of which affect the amount of radiant energy available to the Earth's climate system, as well as the natural internal variability of the climate system.We emphasize that climatic changes alone are unlikely to be the sole determinant cause of a given society's response -whether abandonment of settlements or bellicose action against its own members or neighbors. Often, the natural hazard is simply a catalyst for actions whose groundwork had been set in motion for some time prior. In many cases, appropriate mitigation to reduce vulnerability and efforts to enhance a society's adaptive capacity might have been enough to prevent the most extreme consequences of the nature's extremes. In that vein, we point to current conditions in the western United States, where a complex mix of past and current actions together with a rapidly changing climate are causing a plethora of problems whose solution will demand creative collaborative actions at all levels of society.Evidence of the influence of climatic variability and change in human affairs is as old as the available history of human kind. 1 In recent decades, interest in documenting and understanding possible links between climate variability and societal responses has been heightened by the rise of concern for the effects of anthropogenic climate change (also commonly referred to as global warming). 2 The rapid warming and extreme weather being experienced in many parts of the world 3 have led many to look to the past for clues of potential future impacts of global warming 4 while at the same time focusing on human activities that may have enhanced their vulnerability to climatic extremes. 5 We note that there are many published works that cover the general topic of environmental changes leading to various degrees of impacts on societies past and present. 6 These and many other works amply demonstrate that societal responses to environmental stressors are rarely, if ever, linear. Human societies are complex systems that may or may not respond to those stressors in appropriate and effective ways. Our goals for writing this article are twofold. We highlight some recent pa...

A composite annual-resolution stalagmite record of North Atlantic climate over the last three millennia

“…For example, although we recognise that climatic changes alone are unlikely to be the sole driver for societal change25, it is noted that the positive NAO phase at ~290-550 CE is coincident with the decline of the Roman Empire and the European Migration period. This was followed by generally negative NAO conditions in the period 600-900 AD, which would provide suitable conditions for westward expansion in the north Atlantic region.…”

Reconstructing Late Holocene North Atlantic atmospheric circulation changes using functional paleoclimate networks

“…Prior to presenting some further thoughts on corresponding relationships, we emphasize that one has to keep in mind, that climatic conditions have almost never been the sole reason for societal changes. However, they can be either beneficial or disadvantageous, also depending on how vulnerable a society is to environmental disruptions (Diaz and Trouet, 2014;Weiss and Bradley, 2001;Diamond, 2005). Because of the complex interrelationship between human societies and environmental and climatic factors (Engler, 2012;Engler and Werner, 2015), discussions about any possible causal links would in general be highly speculative, so that we explicitly refrain from making any corresponding claims.…”

“…decreasing temperatures, together with more frequent droughts following the RWP might have progressively added stress to societies in the Western Mediterranean, which had already been weakened by internal conflicts, plagues, invasions and other factors at this time (McCormick et al, 2012a;Diaz and Trouet, 2014). López-Moreno and Vicente-Serrano (2008) describe that a corresponding effect could have played a key role not only in the Western Mediterranean, but also in the Northern Balkan region.…”

French summer droughts since 1326 CE: a reconstruction based on tree ring cellulose <i>δ</i><sup>18</sup>O

“…Droughts can have severe impacts on ecosystems and on human activities (Büntgen et al, 2010;Seneviratne et al, 2012;Diaz and Trouet, 2014), as they influence water availability, groundwater recharge, algal blooms (Paerl et al, 2011), forest productivity (Allen et al, 2010), carbon sink saturation (Nabuurs et al, 2013), crop yields, forest fires, soil degradation, building subsidence and insurance costs (Corti et al, 2011(Corti et al, , 2009, as well as human health (Haines et al, 2006;OBrien et al, 2014). More intense and longer meteorological droughts have already been identified in southern Europe (Sousa et al, 2011; and southern France (Giuntoli et al, 2013) in past decades.…”