According to Ljungqvist et al. (2012), “a number of Northern Hemispheric (NH) temperature reconstructions covering the last 1-2 millennia, using temperature-sensitive proxy data, have been made to place the observed 20th century warming into a long-term perspective.”
And they say that “these studies generally agree on the occurrence of warmer conditions ca. 800-1300 AD and colder conditions ca. 1300-1900 AD, followed by a strong warming trend in the 20th century,” noting that “the earlier warm period is usually referred to as the Medieval Warm Period … whereas the later colder period is usually referred to as the Little Ice Age).” In addition, and “related to this issue,” as they continue, “is the question of whether or not the current warmth has exceeded the level and geographic extent of the warmth in the last millennium,” i.e., that of the Medieval Warm Period.
