This confirms what I’ve been saying years, that underwater volcanoes can lead, not only to cooling, but to ice ages.
Researchers presented underwater volcanism as the reason why the sky went dark for more than a year beginning 536 A.D. At that time, some parts of Europe and Asia saw the Sun for only about four hours a day, and even when the Sun was visible, accounts say it gave no more light than the Moon for 18 months. The dimming led to catastrophic global cooling, famine, and civil upheavals in Medieval times.
This period of darkness and cooling marked the beginning of a longer period from 536 to 555 A.D. as trees struggled to grow, indicating that the dimming was extensive.
536 A.D. was also one of the worst periods to be alive, according to Harvard University medieval historian Michael McCormick, who is not part of the study.
“People thought it was the end of the world,” said Dallas Abbott who studies paleoclimate and extraterrestrial impacts at Columbia University’s Lamont-Doherty Earth Observatory.
Abbott and her colleague John Barron from the USGS said their study of a Greenland ice core (GISP2) pointed to underwater eruptions near the equator that carried calcium-laden sediments and microscopic sea creatures into the atmosphere, which helped dim the sunlight.
“We found by far the most low-latitude microfossils that anybody’s ever found in an ice core,” said Abbott.
Thanks to Guy Wilson for this link
“New ice core evidence for a volcanic cause of the A.D. 536 dust veil” – Larsen et al. – Nature – DOI: 10.1029/2007GL032450
New and well‐dated evidence of sulphate deposits in Greenland and Antarctic ice cores indicate a substantial and extensive atmospheric acidic dust veil at A.D. 533–534 ± 2 years. This was likely produced by a large explosive, near equatorial volcanic eruption, causing widespread dimming and contributing to the abrupt cooling across much of the Northern Hemisphere known from historical records and tree‐ring data to have occurred in A.D. 536. Tree‐ring data suggest that this was the most severe and protracted short‐term cold episode across the Northern Hemisphere in the last two millennia, even surpassing the severity of the cold period following the Tambora eruption in 1815.