Posted: February 11th, 2012 by Militant Libertarian
A paper published this week in the journal Climate of the Past analyzes an “unprecedentally large network of temperature…proxy records” [a total of 120] and concludes that warming of the 20th century was “within the range of natural variability over the last 12 centuries.” Only two of the eight types of temperature proxies analyzed indicate 20th century warming exceeded that of the Medieval Warming Period.
Northern Hemisphere temperature patterns in the last 12 centuries
F. C. Ljungqvist1,2, P. J. Krusic3,4, G. Brattström5, and H. S. Sundqvist3,4
1Department of History, Stockholm University, 106 91 Stockholm, Sweden
2Centre for Medieval Studies, Stockholm University, 106 91 Stockholm, Sweden
3Bert Bolin Centre for Climate Research, Stockholm University, 106 91 Stockholm, Sweden
4Department of Physical Geography and Quaternary Geology, Stockholm University, 106 91 Stockholm, Sweden
5Department of Mathematics, Stockholm University, 106 91 Stockholm, Sweden
Abstract. We analyze the spatio-temporal patterns of temperature variability over Northern Hemisphere land areas, on centennial time-scales, for the last 12 centuries using an unprecedentedly large network of temperature-sensitive proxy records. Geographically widespread positive temperature anomalies are observed from the 9th to 11th centuries, similar in extent and magnitude to the 20th century mean. A dominance of widespread negative anomalies is observed from the 16th to 18th centuries. Though we find the amplitude and spatial extent of the 20th century warming is within the range of natural variability over the last 12 centuries, we also find that the rate of warming from the 19th to the 20th century is unprecedented. The positive Northern Hemisphere temperature change from the 19th to the 20th century is clearly the largest between any two consecutive centuries in the past 12 centuries.