A new report published this month in Science, 2500 Years of European Climate Variability and Human Susceptibility, suggests that climatic variability coincided with the collapse of the Western Roman Empire.
Climate variations have influenced the agricultural productivity, health risk, and conflict level of preindustrial societies. Discrimination between environmental and anthropogenic impacts on past civilizations, however, remains difficult because of the paucity of high-resolution palaeoclimatic evidence. Here, we present tree ring–based reconstructions of Central European summer precipitation and temperature variability over the past 2500 years. Recent warming is unprecedented, but modern hydroclimatic variations may have at times been exceeded in magnitude and duration. Wet and warm summers occurred during periods of Roman and medieval prosperity. Increased climate variability from ~AD 250 to 600 coincided with the demise of the Western Roman Empire and the turmoil of the Migration Period. Historical circumstances may challenge recent political and fiscal reluctance to mitigate projected climate change.
Science Now provides the following discussion of the implications of this study in the article Fall of Rome Recorded in Trees -- with the interesting observation that "By counting wood samples, the analysis also created a rough measure of human activity. In eras of prosperity, more trees were cut down for building and fuel, yielding more samples in the archaeological record. At other times, like the years after the Black Death and the so-called Migration Period between 300 C.E. and 600 C.E. when the Roman Empire was overwhelmed by tribes pushing in from the east, the number of wood samples dwindles to nearly nothing. "It's an interesting proxy of demographic trends and really the most provocative part of the study," says Stahle."