Short answers, pulled from the story.
The era spanning from 950 CE to 1250 CE marked a distinct period of warmth in the North Atlantic region. Historians and scientists refer to this interval as the Medieval Warm Period, though some prefer the term Medieval Climate Anomaly.
Hubert Lamb published foundational research on this topic in 1965 using data from botany and historical documents. He analyzed prevailing temperatures and rainfall patterns in England around specific years within that timeframe.
Vikings founded Eastern and Western Settlements near the southern tip of Greenland around 985. In early stages, these communities kept cattle, sheep, and goats with about a quarter of their diet coming from seafood.
Researchers rely on ice cores, tree rings, and sediment records to reconstruct past temperatures before modern instruments existed. Lloyd D. Keigwin conducted a 1996 study of radiocarbon-dated box core data from marine sediments in the Sargasso Sea.
The Medieval Warm Period ended as a regionally cooler period emerged in the North Atlantic and elsewhere known as the Little Ice Age. Much of the Northern Hemisphere showed significant cooling during this subsequent phase defined from 1400 to 1700.