Ancient and Medieval Climate Change and the Future of Humanity
Paper by Michael McCormick
Given at The Encounter of Science and History, Harvard University, on November 1, 2013
Historians are supposed to be specialists of the written sources and focus on the past, not the future. Until very recently, historians and archaeologists generally assumed that climate was stable and could be left out of the variables that we explore to explain change in past societies. Today archaeologists and historians are expanding their evidentiary base to include the material evidence of archaeology and especially the new data from modern climate science which aims to reconstruct past climates from scientific proxies that preserve climate signals: tree rings, ice cores, etc. The rapid advance of climate science is producing amazing amounts of entirely unanticipated and increasingly precise information about unambiguous climate changes in the historical past that reveal abrupt or gradual shifts in temperatures, precipitation, and growing seasons that impacted human societies and economies over the short and long term by affecting food production, disease ecologies, and communications networks (storminess and navigation, closing of Alpine passes, etc.). When incorporating this growing scientific paleoclimate data into investigations of ancient and medieval economies and societies, we must respect the complexities of the evidence, the patterns of causation, and the differing degrees of resilience that societies displayed in the deeper past. Some examples of recent scientific and historical investigations of ancient and medieval climate demonstrate the power of combining scientific and traditional historical evidence. Before ca. 1500 A.D., even the richest troves of written records have not sufficed for detailed climate reconstruction. They can however play an invaluable role in validating modern climate science. By working together with climate scientists to test, confirm or improve scientific reconstructions of past climate change, historians can help calibrate climate science’s efforts to understand present and future trends.