Two volcanoes trigger crises of the late antiquity

http://www.eurekalert.org/pub_releases/2016-04/hcfo-tvt041816.php

Public Release: 19-Apr-2016
Two volcanoes trigger crises of the late antiquity
International team of climate researchers reconstruct global cooling in the reign of emperor Justinian
Helmholtz Centre for Ocean Research Kiel (GEOMAR)

Contemporary chroniclers wrote about a "mystery cloud" which dimmed the light of the sun above the Mediterranean in the years 536 and 537 CE. Tree rings testify poor growing conditions over the whole Northern Hemisphere - the years from 536 CE onward seem to have been overshadowed by an unusual natural phenomenon. Social crises including the first European plague pandemic beginning in 541, are associated with this phenomenon. Only recently have researchers found conclusive proof of a volcanic origin of the 536 solar dimming, based on traces of volcanic sulfur from two major eruptions newly dated to 536 CE and 540 CE in ice cores from Greenland and Antarctica.

•••••

the impact of the volcanic double event of 536/540 on Northern Hemisphere climate was stronger than any other documented or reconstructed event of the past 1200 years. "One of the eruptions would have led to a significant cooling of the Earth's surface. Two of them, so close in time, caused what is probably the coldest decade of the past 2000 years," says Dr. Matthew Toohey from GEOMAR, lead author of the study today at a press conference at the annual EGU Meeting in Vienna where he presented the results.

•••••

The relationship between the "mystery cloud" of 536 and the transition from Antiquity to the Middle Ages is an issue of great popular interest. Volcanic eruptions in the more recent past have impacted human societies. For example, in 1815 the Indonesian volcano Tambora hurled so much ash and sulfur into the atmosphere that the year 1816 became known as "the year without summer" in Europe and North America, where unusually low temperatures led to crop failures and famines.

•••••