The few literate cultures in AD 536 recorded intense cold, crop failures, starvation, and deaths. About 75 percent of the people in a northern Chinese kingdom died. Similar problems were reported around the Mediterranean. Tree rings in North America, Europe, and Asia record 15 years of cold beginning in AD 536. Ice cores in Greenland and in Antarctica record a dramatic increase in sulfur in the same year, indicating a volcanic eruption was the cause, and not an asteroid impact. The worldwide sulfur circulation indicates an eruption in a tropical latitude, and the greater sulfur in Greenland indicates an eruption north of the equator. El Salvador's Ilopango eruption, which appears to have occurred more recently than the 5th century, is the likely candidate for the worst worldwide disaster in the past few millennia.