Eruptions create clouds of sulfuric acid in the upper atmosphere and can cool the climate – sciencedaily


Volcanic eruptions have contributed to the collapse of dynasties in China over the past 2,000 years by temporarily cooling the climate and affecting agriculture, according to a study co-authored by Rutgers.

Large eruptions create a cloud that blocks sunlight for a year or two. This reduces the warming of land in Asia in summer and leads to a weaker monsoon and less rainfall, which reduces harvests.

“We first confirmed that dynasty collapses in China over the past 2,000 years are more likely in the years following volcanic eruptions,” said co-author Alan Robock, professor emeritus in the Department of environmental sciences from the School of Environmental. and biological sciences at Rutgers University-New Brunswick. “But the relationship is complex because if there are wars and conflicts going on, dynasties are more likely to collapse. The impact of a chilled climate on crops can also make conflicts more likely, increasing still the likelihood of collapse. “

Scientists reconstructed 156 explosive volcanic eruptions from AD 1 to 1915 by examining the high levels of sulfate in ice cores from Greenland and Antarctica, according to the study published in the journal. Earth & Environment Communications. Scientists also analyzed historical documents from China on 68 dynasties and examined the war between 850 and 1911 there.

Erupting volcanoes can pump millions of tonnes of sulfur dioxide into the upper atmosphere, forming vast clouds of sulfuric acid that reflect sunlight and the average temperature of the Earth’s surface.

Major eruptions can lead to “a double risk of severe cold and drought during the agricultural growing season,” according to the study. The impacts can be compounded by the death of livestock, accelerated land degradation and further damage to crops from agricultural pests that survive during milder winters.

Scientists have found that smaller volcanic “shocks” to the climate can cause dynasties to collapse when political and socio-economic stress is already high. Larger shocks can lead to collapses without substantial pre-existing stress. Other factors include poor leadership, administrative corruption and demographic pressures.

An influential Chinese concept, the “Heaven Mandate”, allowed for some continuity between dynasties. The elites and “commoners” more readily accepted a new dynasty which, by seizing power, demonstrated a divine mandate to rule that the old dynasty had lost.

The scientists’ findings underscore the need to prepare for future eruptions, especially in areas with economically vulnerable populations (perhaps comparable to the Ming and Tang dynasties in China) and / or that have a history of mismanagement of resources, as in Syria before the 2011 uprising which may have been partly triggered by the drought.

Eruptions during the 20th and 21st centuries were smaller than many during Imperial China. Yet moderate eruptions may have contributed to the Sahelian drought of the 1970s to 1990s, causing an estimated 250,000 deaths and resulting in 10 million refugees in this economically marginalized region. Future major eruptions, combined with climate change, are likely to profoundly affect agriculture in some of the most populous and marginalized regions of the planet, according to the study.

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Material provided by Rutgers University. Original written by John Cramer. Note: Content can be changed for style and length.

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