Read here. Map source here. Numerous temperature reconstructions indicate that during the Medieval centuries, two distinct warming intervals happened. New research from a Scottish loch's sediment core analysis identified the two separate, extended warming periods between 900 and 1600AD.
In addition, the new peer-reviewed research clearly reveals the wide climate variation experienced prior to the large industrial CO2 emissions of the 20th century. The modern warming was found not to be unusual or out of the ordinary. (click on image to enlarge)
"“The Loch Sunart reconstruction for the late MCA suggests temperatures from AD 916 to 1035 were similar to those recorded over the late twentieth century.”..... Cage and Austin [Cage, A.G. and, W.E.N. Austin. 2010] point out “perhaps the most distinctive feature of the Loch Sunart temperature record is the short-lived event between AD 1540 and1600, which is characterized by a very abrupt warming transition at AD 1540. This period had an average temperature anomaly of 1.1ºC above the long-term mean, which is higher than most of the 20th century and the late MCA.”....."“The Loch Sunart temperature reconstruction exhibits a gradual cooling trend that continues from AD 1608 to 1941, with the coldest temperature anomalies (~0.75ºC) of this period occurring between the early 1930s and 1940s.” So in the last 400 years, the sea bottom of Loch Sunart cooled, the coldest period over the past 400 years occurred 70 years ago, and then the water warmed up to levels that were typical during the beginning of the 400-year period."
Additional climate history postings. Historical temperature charts.