ENVIRONMENT
The 536 Dust Veil
536 CE
History · Middle Ages · Holocene · Meghalayan
In 536, a volcanic eruption dimmed the sky for months, and Byzantine witnesses compared the brightness of the sun to that of the moon.
The 536 dust veil designates the atmospheric dimming observed that year over several months, described by Byzantine witnesses comparing the brightness of the sun to that of the moon. Tree rings and ice cores establish its cause, a volcanic eruption of large magnitude. The mechanism is known: an eruption of that size injects sulphur into the stratosphere, where it forms fine droplets that reflect sunlight back to space for one to two years, at an altitude precipitation does not reach. Further eruptions follow in 540 and 547. Tree rings from the Alps and from the Altai, a mountain range of Central Asia, then record a cooling of more than a century. In the simulations of van Dijk and colleagues, a mathematical model of the climate applied to the eruptions of the sixth and seventh centuries gives a cooling of only about twenty years, as does a compilation of tree rings from across the northern hemisphere. Harvests are affected, and the Justinianic plague occurs five years after the first episode.
Why it matters
The episode associates within a few years a volcanic forcing, a food crisis, a pandemic and political difficulties in several states, from the Eastern Roman Empire to Sasanian Persia. It further documents the passage from an event known through narrative sources alone to an event measured, dated and attributed by natural archives.
Dating & uncertainty
Northern hemisphere tree rings place the most marked cooling between mid-July and early August 536. That precision follows from the nature of the medium: a ring records the growth of an entire season, so an abrupt cooling leaves a mark at a measurable position within the annual ring. Büntgen and colleagues, who named it the Late Antique Little Ice Age (the little ice age at the end of Antiquity), describe a cold phase opened by the eruptions of 536, 540 and 547 and lasting until about 660, probably prolonged by the ocean and sea ice, which kept the cold going once it had set in, and by a period of weak solar activity. In the southern hemisphere, studies of wood anatomy, the structure of the cells laid down in each ring, do not find the mark of the 536 cooling, and the reason for its absence has not been established.
Our species’ history as one day
23:53:116 min 49 s before midnight
if the 315,000 years of Homo sapiens were compressed into a single day