What was the Medieval Warm Period, and how did it shape world history?

The answer

The Medieval Climate Anomaly (MCA), spanning approximately 900 to 1300 CE, brought temperatures 0.5–1°C warmer than the preceding centuries to much of the Northern Hemisphere. This warmth enabled Norse settlement of Greenland around 985 CE under Erik the Red, English wine production as far north as Yorkshire, and bumper harvests that fueled Europe's population boom from 35 million to 80 million. In the Americas, the Cahokia civilization near modern St. Louis peaked around 1100 CE with a population of 20,000. However, the MCA brought devastating drought to the American Southwest, contributing to the abandonment of Ancestral Puebloan settlements at Mesa Verde. The subsequent Little Ice Age (1300–1850 CE) reversed many gains, triggering famine and the Norse abandonment of Greenland by 1450.