What Two Millennia of Chinese Dynasties

 

Wars, revolutions and assassinations can trigger regime change but climate events destroy societies.

A paper, published in the journal Nature, traced major volcanic events over two millennia that had global impacts. The timing matched major upheavals from ancient Egypt to dynastic China.

What stunned [Joseph Manning, a Yale Egyptologist], was that the paper recalibrated earlier chronologies by seven to eight years, so that dates of the eruptions neatly coincided with the timing of well-documented political, social, and military upheavals over three centuries of ancient Egyptian history. The paper also correlated volcanic eruptions with major 6th century A.D. pandemics, famines, and socioeconomic turmoil in Europe, Asia, and Central America. The inescapable conclusion, the paper argued, was that volcanic soot — which cools the earth by shielding its surface from sunlight, adversely affecting growing seasons and causing crop failures — helped drive those crises.

Since then, other scholarly papers relying on paleoclimatic data— most of it drawing on state-of-the-art technologies originally designed to understand climate change — have found innumerable instances when shifts in climate helped trigger social and political tumult and, often, collapses. The latest is a paper⁠ published last month⁠ in Communications Earth and Environment that posited “a systematic association between volcanic eruptions and dynastic collapse across two millennia of Chinese history.”

The study found that 62 of 68 dynastic collapses⁠ occurred soon after Northern Hemisphere volcanic eruptions, an outcome that had only a one-in-2,000 chance of happening if the eruptions and collapses were unrelated. Chinese have traditionally cited the withdrawal of the “mandate of heaven” to explain the cold weather, droughts, floods, and agricultural failures that seemed to accompany the fall of dynasties. The paper contends that those phenomena have a climatic explanation.

All these papers are propelled by a nearly-decade-long revolution in climate science technology. A blizzard of quantitative data from “climate proxies” — ice cores, tree rings, cave stalagmites and stalactites, and lake, bog, and seabed sediments — has upended the way some historians do their work.

...To tap that data, some historians are crossing extensive barriers within their discipline to work with biologists, geologists, geographers, paleoclimatologists, climate modelers, anthropologists, and others. These mold-breaking historians are learning geochemistry and climatology; the scientists they work with are reading history.

Manning now attends more science conferences than history conferences. A paper⁠ he co-authored last year with 19 other natural scientists, historians, and archeologists argued that one of the biggest volcanic eruptions of the last 2,500 years, at Alaska’s Okmok volcano in 43 B.C., resulted in a decade of forbiddingly cold temperatures across the Northern Hemisphere, helped trigger the end of Egypt’s Ptolemaic Kingdom, and hastened the transition from the Roman Republic to the Roman Empire, as Rome gave up some trappings of constitutional government to become an absolute monarchy. As the paper explained, “The wet and very cold conditions from this massive eruption on the opposite side of Earth probably resulted in crop failures, famine, and disease, exacerbating social unrest and contributing to political realignments across the Mediterranean region at this critical juncture of Western civilization.”