From CO2 Science
Medieval Droughts of the Western United States and concluded that there is nothing unusual, unnatural or unprecedented about the nature of drought during the Current Warm Period, in contradiction of the unfounded claim of the world's climate alarmists to the contrary. Read
Kleppe, J.A., Brothers, D.S., Kent, G.M., Biondi, F., Jensen, S. and Driscoll, N.W. 2011. Duration and severity of Medieval drought in the Lake Tahoe Basin. Quaternary Science Reviews 30: 3269-3279.
The authors write that "evidence for medieval droughts of duration and magnitude much larger than those in the instrumental record has been reported throughout much of the world, but a particularly robust signal is expressed in the western United States (e.g., Cook et al., 2010; Woodhouse et al., 2010)," and they say that "this period of pronounced aridity, the Medieval Climate Anomaly of Stine (1994), is best expressed between ~ 800 and 1250 AD," when "the centennial average precipitation decreased to 75% and decadal averages decreased to 60% of twentieth-century values (Graham and Hughes, 2007)."
What it means
Considered in their entirety, the several findings of Kleppe et al. (and many others who they cite) suggest that the Medieval Climate Anomaly - or Medieval Warm Period - experienced far less precipitation and far longer and more severe drought than what has been experienced to date in the Current Warm Period. In addition, their data suggest that such dry conditions have occurred regularly, in cyclical fashion, "every 650-1150 years during the mid- and late-Holocene." And all of these observations suggest that there is nothing unusual, unnatural or unprecedented about the nature of drought during the Current Warm Period, in contradiction of the unfounded claim of the world's climate alarmists to the contrary.
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