The Leshan Giant Buddha in Sichuan, China, a relic of the Tang dynasty, which collapsed in 907 A.D. amid changes in the climate. ZHONG ZHENBIN / ANADOLU AGENCY / GETTY IMAGES
Thanks to Jacques Leslie
Climate Clues from the Past Prompt a New Look at History
A fragment from a sculpted stele, an artifact of the Akkadian Empire, which collapsed in the 22nd century B.C. amid a severe drought. MBZT VIA WIKIPEDIA
As scientists rapidly improve their ability to decipher past climate upheaval through ice cores and other “proxies,” historians are re-examining previous political and social turmoil and linking it to volcanic eruptions, prolonged droughts, and other disturbances in the natural world.
Joseph Manning, a Yale University professor of ancient history, likes to recall the moment when he was shown an advance copy of a scholarly paper that pinpointed the timing of major volcanic eruptions over the last 2,500 years. As he read the paper, “I literally fell off my chair,” he said recently.
Roman coins dating to 82 B.C. Lead from smelting such coins has been found in faraway ice cores, offering clues about Roman history. CARLOMORINO VIA WIKIPEDIA
Relying on new geochemical techniques for analyzing ice core sediment to determine the dates of ancient volcanic activity down to the year or even season, the paper, published in Nature in 2015, showed that major eruptions worldwide caused precipitous, up-to-a-decade-long drops in global temperatures. Later research pegged those drops at as much as 13 degrees F.
What stunned Manning, an 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.”
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