In the 1980s, assessments of Antarctic ice did not turn up major mid sixth-century volcanism, but rather a signal from about 505 CE. Even before it seemed the dust veil witnessed (inconsistently) over the Mediterranean was not a volcanic dust veil, but instead some sort of "damp fog," the mountain was considered an unlikely source. They also found it in sulphate in Greenlandic ice, and they discovered pumice-lodged wood they date to 540 ☙0 CE (meaning give or take 90 years), on Rabaul, a volcano in Papua New Guinea. NASA geoscientists Richard Stothers and Michael Rampino discovered a stratosphere-clouding volcanic episode tucked away in four (but, by 1988, five) late antique texts. Their mysteriousness, however, has spurred intense interest from scholars and enthusiasts since the phenomenon first appeared in the pages of the Journal of Geophysical Research, in 1983. These reports leave room to doubt that the phenomenon they describe was really volcanic in origin. The Roman statesman Cassiodorus, for example, describes a dim moon, and a sun that lost its "wonted light" and appeared "bluish," as if in "transitory eclipse throughout the whole year." They merely describe in vague terms a sort of unusual sun dimming or atmospheric veiling. Often the culpable volcano (or volcanoes) is not known, and firsthand accounts (if any) are more than vague: they are cryptic.įor example, something traumatic appears to have affected the world in around the year 536 CE. The five reports that survive for this "536 event" say nothing of an eruption. Yet these episodes are far more mysterious. There were other large events, deeper in the historical past. A recent study estimated that it resulted, in some regions, in 2 to 4 degrees Celsius of cooling from June to August, 1816.
Nevertheless, scientists have determined that it was one of the biggest volcanic episodes of the last several thousand years. While the available instrumental data are useful, they are limited and local. There are fewer firsthand accounts, and no films or photos (though some argue Joseph Turner and other artists captured its far-reaching atmospheric effects). No volcanologist or climate scientist doubts it dwarfed Pinatubo, but far less is known about the earlier eruption. Take Tambora, which erupted in April 1815 and pumped 60 to 110 megatons of sulphur dioxide into the air, leading to one of the most infamous ‘Years Without a Summer’. Earlier and much larger volcanic eruptions in the late Holocene are more obscure. In the Northern Hemisphere, temperatures in summer 1992 fell by about 2 degrees Celsius. 5 degrees Celsius that was still in effect as late as late 1992. That heated the stratosphere but cooled Earth's surface. The volcano caused a sudden (but non-uniform) fall in average global temperatures of at least. While there, they "veiled" the sun by absorbing or "backscattering" solar radiation. The aerosols were suspended in the atmosphere for around two years.
It turned into fine sulphuric acid aerosol, and, within weeks, enveloped much of the Earth. Pinatubo released up to 20 megatons of sulphur dioxide as many as 35 kilometers into the sky. The eruption was photographed from the ground and the air, and today you can even YouTube it. There are living witnesses, newspaper articles, detailed surveys of the mountain before and after it blew its top, and satellite maps of the ejecta. The June 1991 Pinatubo eruption in the Philippines was one of the largest volcanic eruptions of the twentieth century.
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