Winter was coming. In AD 536, the first of three massive volcanic eruptions ushered in a mini ice age. It coincided with an epidemic of the plague, the decline of the eastern Roman Empire, and sweeping upheavals across Eurasia.
Now we have the first evidence that the disruption to climate continued a lot longer than a decade, as was previously thought. The extended cold period lasted until around 660, affecting Europe and Central Asia, and perhaps the rest of the world too.
The work builds on research that used ice cores to identify three significant volcanic eruptions in the years 536, 540 and 547. Now Ulf Büntgen at the Swiss Federal Research Institute in Birmensdorf and his colleagues have used tree ring data from Europe and Central Asia to show that decades of cooler summers – in some cases 4 °C cooler – ensued, probably caused by volcanic particulates in the atmosphere.