To climatologists, the period of seven to twelve centuries ago was known as a "Climate Anomaly" or a "Warm Period" (800-1300 CE). To archaeologists, it was a time of great change, a period when cultural patterns were put into place that lasted into the modern era. Although the medieval period is better known in Europe and the Old World, it was a global phenomenon. It happened in the New World, too.
This is a companion discussion topic for the original content at https://www.worldhistory.org/article/2147/medieval-climate-anomaly-in-the-americas/.