Old evidence for the climate sheds new light on history

This story originally appeared on Yale environment 360 and is part of Climate desk cooperation.

Joseph Manning, a professor of ancient history at Yale University, likes to recall a time when he was shown a preliminary copy of a scientific paper that pinpointed the timing of major volcanic eruptions over the past 2,500 years. As he read the paper, “I literally fell out of my chair,” he said recently^,.

Relying on new geochemical techniques to analyze ice core sediments to determine dates of ancient volcanic activity up to the year or even season, the article published in nature in 2015, showed that major global eruptions are causing dramatic, up to a decade^, falling global temperatures. A later study found that these drops were up to 13 degrees F.^,

What surprised Manning, an Egyptologist, was that the document recalibrated earlier chronologies by seven to eight years, so that the dates of the eruptions coincided exactly with the time of well-documented political, social, and military upheavals in three centuries of ancient Egyptian history. The document also links volcanic eruptions to large 6^you century AD pandemics, famines and socio-economic shocks in Europe, Asia and Central America. The inevitable conclusion, the document says, is that volcanic soot, which cools the earth by protecting its surface from sunlight, adversely affects the growing seasons and causes crop failures, has helped fuel these crises.

Since then, other paleoclimatic research papers – most of which are based on state-of-the-art technology, originally designed to understand climate change – have found countless instances where climate change has helped provoke social and political unrest and often collapse. The last is paper^, published last month^, in Communications Earth and environment which sets out “a systematic link between volcanic eruptions and dynastic collapse over two millennia of Chinese history.”

The study found that 62 of the 68 dynastic collapses^, occurred shortly after the volcanic eruptions in the Northern Hemisphere, a result that there was only one in 2,000 chances of occurring if the eruptions and collapses were not related. The Chinese have traditionally cited the withdrawal of the “heavenly mandate” to explain the cold weather, droughts, floods and agricultural failures that appear to accompany the fall of the dynasties. The document claims that these phenomena have a climatic explanation.

All of these articles are driven by a nearly decade-long revolution in climate technology. A swarm of quantitative data from “climate mediators” – ice cores, tree rings, cave stalagmites and stalactites and lake sediments, swamps and seabeds – has changed the way some historians do their work.

Joe McConnell, who runs an innovative ice core research laboratory at the Reno Desert Research Institute in Nevada, believes climate data offers historians what DNA evidence provides to the judiciary: an indisputable, objective source of critical information. Like DNA evidence that overturns a conviction, McConnell said, climate data is information that historians “must accept.”

To take advantage of this data, some historians go through extensive barriers within their discipline to work with biologists, geologists, geographers, paleoclimatologists, climate modelers, anthropologists, and others. These mold-breaking historians study geochemistry and climatology; the scientists they work with read history.