Read here. Map source here. Using sediment cores from lakes, researchers identified distinct periods of climate change, including the Dark Ages, Medieval Warming Period and the Little Ice Age. This peer-reviewed study, like so many, is contrary to the speculative comments by IPCC Climategate scientists who claimed that the MWP was only a northern European phenomenon.
"...the authors measured a number of sediment properties, among which were sulfur content and coarse mineral grains, the former of which served as a proxy for paleo-Asian summer monsoon activity and the latter of which served as a proxy for paleo-Asian winter monsoon activity. This work revealed the presence of a cold/dry interval stretching from AD 1 to 750, a warm/humid interval stretching from AD 750 to 1200, and another cold/dry interval stretching from AD 1200 to the present, which periods they associated, respectively, with "the Dark Ages Cold Period, the Medieval Warm Period and the Little Ice Age ." [Yamada, K., Kamite, M., Saito-Kato, M., Okuno, M., Shinozuka, Y. and Yasuda, Y. 2010]
Other climate history postings. List of peer-reviewed study postings. Historical temperature charts.