Looking on the wweb to see if I can find something on that specific show I saw.
Failing to do that yet. I did find this. which is close tot he same thing.
"From around 800 A.D. to 1200 or 1300, the globe warmed again considerably and civilization prospered. This warm era displays, although less distinctly, many of the same characteristics as the earlier period of clement weather. Virtually all of northern Europe, the British Isles, Scandinavia, Greenland, and Iceland were considerably warmer than at present. The Mediterranean, the Near East, and North Africa, including the Sahara, received more rainfall than they do today. During this period of the High Middle Ages, most of North America also enjoyed better weather. In the early centuries of the epoch, China experienced higher temperatures and a more clement climate. From Western Europe to China, East Asia, India, and the Americas, mankind flourished as never before.
This prosperous period collapsed at the end of the thirteenth century with the advent of the "Mini Ice Age" which, at its most frigid, produced temperatures in central England for January about 4.5deg.F colder than today. Although the climate fluctuated, periods of cold damp weather lasted until the early part of the nineteenth century. During the chilliest decades, 5 to 15 percent less rain fell in Europe than does normally today; but, due to less evaporation because of the low temperatures, swampy conditions were more prevalent. As a result, in the fourteenth century the population explosion came to an abrupt halt; economic activity slowed; lives shortened as disease spread and diets deteriorated"
http://www.stanford.edu/~moore/history_health.html
