Earth knows how to balance its climate after volcanic eruptions that trigger ash and acid into the sky. As the Sun gets blocked by the cloud of ash, it eventually results in a cold climate spanning over decades, changing the climate and ancient examples are aplenty, say researchers from the Niels Bohr Institute.
Citing the fact from ancient times when a year of extreme cold followed after a violent volcanic eruption in the year 44 BC – the year Julius Caesar died, researchers from the Niels Bohr Institute said the effects of volcanic eruptions are greater than previously thought.
As American pine trees can live for thousands of years, the narrow and irregular growth rings in the middle of the picture shows a year of extreme cold weather after a violent volcanic eruption in the year 44 BC – the year Julius Caesar died, they explained.
From their new volcanic reconstruction, it was realized that large volcanic eruptions in the high northern latitudes, such as on Iceland or in North America, often caused severe summer cooling in the northern hemisphere. History is replete with such events, they said.
Past temperatures in the ice cores drilled out of the ice sheets in Greenland and Antarctica due to snow fall for years form into an ice layer, cooling the atmosphere.
“The ice is an archive of past climate, but it is also an archive of past volcanic eruptions, as we can find traces of eruptions in the ice cores we drill out of the ice sheets in the form of ash and acid layers, which fell from the atmosphere with the precipitation,” explains Dorthe Dahl-Jensen of the Centre for Ice and Climate at the Niels Bohr Institute at the University of Copenhagen, which is leading the ice core drilling in Greenland.
Similarly, trees contain annual information on past temperatures as the thickness and density of each annual tree-ring depends on how warm or cold the summer was, and in this way, they provide temperature records from e.g. Europe showcasing the past record delving into several thousands of years.
Based on data from more than 20 ice cores from both Greenland and Antarctica, Dorthe Dahl-Jensen, researcher of the NEEM drilling project, Greenland, has recorded the acidic content in the NEEM core by measuring the electrical conductivity across the ice core to reconstruct the yearly volcanic activity for the last 2,500 years based on data from more than 20 ice cores from both Grenland and Antarctica.
“With the newly developed timescale, we can see that the ice cores previously had been dated incorrectly by up to 10 years during the first millenium and this caused problems when they tried to compare the volcanic eruptions with their climatic impact seen from the climate archive of the tree rings,” says Mai Winstrup, PhD from the Niels Bohr Institute at the University of Copenhagen and now working at the University of Washington in Seattle.
For instance, volcanic ash particle from the NEEM ice core, Greenland was found at a depth of 327 meters, equivalent to 536 AD. And it came from a volcano located along the west coast of North America, said researchers.
When Francis Ludlow, historian from the Yale Climate and Energy Institute, co-examined historical written records for clues that might indicate volcanic activity from documented evidence from China, Babylon (Iraq) and Europe, he was aghast to find unusual atmospheric observations, such as periods with less sunshine or deep red sunsets, which could have been caused from volcanic ash in the atmosphere.
From March 536 AD, a ‘mystery cloud’ was observed over the Mediterranean for 18 months, they revealed pointing its possibility from a volcano leading to colder temperatures throughout the northern hemisphere. A tablet from the Babylonian (Iraqi) astronomical diary mentions the observation of Halley’s comet in 164 BC as well as atmospheric events, such as a darkened sun caused by a volcanic eruption in 254 BC.
Michael Sigl, Desert Research Institute, Reno explains that this cooling intensified when a tropical volcano erupted 4 years later. In combination, these two volcanic eruptions caused unusually cold summers across the entire northern hemisphere lasting for almost 15 years and resulting in widespread famine. They may also have contributed to the outbreak of the Justinian Plague that devastated the entire Eastern Roman Empire in the years 541-543 AD and eroded millions of the Mediterranean and the Middle East population.
Volcanoes, thus release heat first into the atmosphre and in about 4 years time make the surroundings cooler thus maintianing climatic balance. said researchers whose study has been published in the scientific journal, Nature.