Volcanic eruptions in the sixth and seventh centuries AD led to a Little Ice Age and dramatic social changes

In recent decades, environmental scientists have been talking about climate change, and mean the warming that is happening almost all over the world. But climate change is not always manifested in warming - a new study, which combined data from several scientific fields, reveals that in the sixth and seventh centuries AD, a small ice age prevailed in the northern half of the planet.

By Dr. Daniel Mader, Zivata - Science and Environment News Agency

In recent decades, environmental scientists have been talking about climate change, and mean the warming that is happening almost all over the world. But climate change is not always manifested in warming - a new study, which combined data from several scientific fields, reveals that in the sixth and seventh centuries AD, a small ice age prevailed in the northern half of the planet.

At that time, the average temperature was three degrees Celsius lower than today. Three degrees may not seem like much, but their significance is as dramatic as the negative effects of an additional three degrees expected with current climate change (in droughts, floods, desertification, strong storms, sea level rise, agricultural crises - and more).

The researchers analyzed data obtained from 65 different measurements, from 7 different and independent fields: growth rings of trees, ice cores of glaciers, materials that sank to the bottom of lakes and seas, stalactites and stalagmites formed in caves, documentation of glacier dynamics (growth, shrinking and movement) and historical documents from around the northern hemisphere of the planet. They discovered that the temperatures in the period examined were particularly low relative to the average of other periods.

Additional data collected from ice cores show that in AD 536, 540 and 547 three strong volcanic eruptions occurred in the Northern Hemisphere (it is not clear from which volcanoes), following which many particles were dispersed in the atmosphere. These particles reflected the sun's radiation and therefore the Earth's surface cooled. This cooling encouraged the spread of sea ice in the Arctic - a process that further contributed to the drop in temperature, because white ice reflects solar radiation into space more than the dark sea. Low solar activity in the seventh century also contributed to the cooling.

Historical climate

The researchers conclude that this unusual and difficult period caused many social changes: agricultural crops did not grow, famine spread and severe winters caused destruction and death. A harsh climate causes the collapse of populations of rodents, which host fleas that carry things (the plague). This breakdown encourages the fleas to find new hosts, such as farm animals and humans. It is believed that this was the reason for the outbreak of plague in Asia first, and in Europe later.
This grim reality encouraged the migration of people and nations, caused revolutions and accelerated the decline of empires. Among the dramatic social events that took place after the beginning of this Little Ice Age, we can mention the spread of the Slavs in Europe, the invasion of Italy by the Lombards, the collapse of the government in Mongolia and China, the spread of the Turks in Asia, the spread of the Arab Empire and the spread of Islam, the fall of Byzantium (the Eastern Roman Empire) and more.

How does the study of the past relate to us? Despite the advanced technology we have today, climate change is expected to cause many changes and shocks in the world in the coming centuries. We are still largely dependent on water, a stable climate and agriculture. We should learn from the past so that we can deal with what will happen in the future.