Various historical documents recount the observation of a "mysterious cloud" observed from March 536 in the Mediterranean regions. This cloud has covered the region for about 18 months.
The cooling of the northern hemisphere was described by Procopius (born in the year 565, died around 500-?), a Byzantine historian, in his writings on the wars with the Vandals: "During this year, a sign of ominous occurred. The Sun gave its light without brightness [...] and it seemed to have as an eclipse, because its rays did not shine. " This climate change, the more prolonged of the past two millennia, characterized by very cold summers over large areas, has led to crop failures and famines.
Following which, there is a period of great migration, a contribution to the spread of the "Plague of Justinian" in the Eastern Roman Empire (the "Plague of Justinian" fell flat from 541 to 767 throughout the basin Mediterranean, with a peak in 592.) ... various factors that precipitated the decline of the Roman Empire.
Until now it was thought that these extremely cold periods were caused or aggravated by major volcanic eruptions, no accurate estimate of the role.
The Byzantine Empire under Justinian - doc histocollège - and the areas of The "Plague of Justinian"
A new study, which was contributed researchers from various countries led by scientists from DRI / Desert Reseach Institute of Nevada, and whose results have just been published in the journal Nature on July 8, revisits the timing of 300 volcanoes in the world, dating back to the beginning of the Roman period, and reveals their climate impact.
The study is based on analysis of more than 20 ice cores drilled in Greenland and Antarctica, the precise dating of the annual tree rings (dendrochronology) and on the study of historical documents. Specialists in fields as different, but complementary, as geology, climate, space but also history, have contributed to this work, which was used to assess possible links between climate variability and human history.
These interdisciplinary work in the area of the volcano-climate have helped to show that fifteen of the sixteen coldest summers in the northern hemisphere, between 500 BC and AD 1000, are following major volcanic eruptions .
Climate disruption of the 6th century was preceded by two volcanic eruptions; yhe cooling was initiated by an eruption in the northern hemisphere around March 536, and intensified by an eruption located in the tropics four years later, attributed to Krakatoa. The cold summers persisted for about 15 years, with the before mentioned social consequences.
Iceland - lava fields left by the eruptions of Eldgjá now covered with moss - photo JM.Mestdagh
The study points to other eruptions with climate action, to name only the best known:
- In the 10th century, the fissure eruption of Eldgjá (934 - 942) will produce 450 megatonnes of sulfur aerosols with climate impact.
- In 1783, the Laki eruption disrupts the climate across Europe, generates a terrible famine, which will be one of the possible causes of the French Revolution.
- In 1815, the eruption of Tambora, in Indonesia, cause a new "year without summer" ... during which 200,000 people perish in Europe, already hit by the Napoleonic Wars.
- The eruption of Mount Pinatubo in 1991 will interfere, this time it seems positively with the global warming caused by humans, lowering the overall temperature of the northern hemisphere.
This study demonstrates if necessary the importance of the action of volcanoes on climate history and that of humanity on the one hand, and secondly the complexity of the volcano-climatology, that requires an action of specialized interdisciplinary teams.
- Nature - Timing and climate forcing of volcanic eruptions for the past 2,500 years -- Nature(2015) doi:10.1038/nature14565 Received 21 November 2014 Accepted 06 May 2015 Published online 08 July 2015 - link
repris par :
- Yale News - New timeline links volcanic eruptions to centuries of cold temperature extremes – link
- 20 link- Les volcans à l'origine de bouleversements sociaux –
- The Independant - Under a cloud: How volcanic ash brought civilisation to its knees - link
Déjà traité sur ce blog :
Volcans et climat : le changement climatique en 535 / 27.06.2011 - link
En liaison :
Los Alamos National Laboratory - Were the Dark Ages Triggered by Volcano-Related Climate Changes in the 6th Century? - Ken Wohletz - link