Distant impact: tropical volcanic eruptions and climate-driven agricultural crises in seventeenth-century Ostrobothnia, Finland

Large tropical volcanic eruptions can have considerable impact on climates and societies far away from the physical source of the eruption. Past examples of how volcanism caused abrupt climatic changes, and how societies responded to such changes, may provide us with potential lessons to help us better prepare for the changes that climate change will bring. This paper explores the climatic, agricultural and societal responses to tropical eruptions in the Finnish province of Southern Ostrobothnia during the seventeenth century. Our results suggest that in the studied area more than half of the seventeenth-century agricultural crises which had traceable human consequences resulted from volcanism caused cooling. A sharp agricultural response followed every large tropical eruption. Moreover, sudden impoverishment, and in some cases even elevated mortality and famine, succeeded these agricultural crises. Thus, there is strong evidence that climatic changes caused by volcanism can directly paralyze sensitive food systems that are based on primary production. In this regard, if geoengineering solutions, like emulating volcanic forcing to cool global climate, are considered to be a future mitigation strategy, the case study presented here stresses the need to explore all possible unintended human consequences of any such solutions.