Volcanic winter of 536

A prolonged cooling episode beginning around 536 CE, likely caused by volcanic aerosols that dimmed sunlight across much of the Northern Hemisphere.

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Volcanic aerosol: Suspended particles and droplets produced by volcanic eruptions that can scatter or absorb sunlight. Sulfate aerosols from an eruption can reduce incoming sunlight and cool the surface.
Ilopango: A volcanic caldera in El Salvador formed by large explosive eruptions. One proposal identifies its Tierra Blanca Joven eruption as a source of the 536 aerosol veil.
Procopius: A sixth-century Byzantine historian whose works describe the reign of Justinian I and contemporary events. His account of the Sun’s diminished brightness is a prominent written witness to 536.
Tree-ring chronology: A sequence of tree-ring measurements dated to exact calendar years. Chronologies show sharply reduced growth in some regions during the mid-sixth century.
Stratospheric sulfate aerosols: Fine sulfuric-acid droplets in the stratosphere that reflect sunlight and can cool Earth’s surface. Their long atmospheric lifetime could sustain the dimming associated with 536.
Tierra Blanca Joven eruption: A major explosive eruption from Ilopango in El Salvador, dated to the sixth century. It has been proposed as a contributor to the cooling that began around 536.
Cassiodorus: A Roman statesman and writer whose letters document life in Ostrogothic Italy in the sixth century. His descriptions of unusual weather and weakened sunlight echo reports linked to the episode.
Greenland ice core: A cylindrical record of Greenland ice containing dated layers of snow, particles, and chemical deposits. Sulfate evidence in Greenland ice helps identify the timing and scale of volcanic activity.
Dendrochronology: The study of dated tree rings to reconstruct past environmental conditions and events. Narrow growth rings provide evidence for severe summers after 536.
536 eruption: A major volcanic eruption inferred from historical and geological evidence and associated with climate cooling around 536 CE. This proposed eruption is the central volcanic trigger in accounts of the episode.