What was done
Noting that "periods of dune reactivation reflect sustained moisture deficits for years to decades and reflect broader environmental change with diminished surface- and ground-water resources (Woodhouse and Overpeck, 1998)," the authors focused on "the largest dune system in North America, the Nebraska Sand Hills," utilizing "recent advances in optically stimulated luminescence dating (Murray and Wintle, 2000) to improve chronologic control on the timing of dune reactivation," while linking landscape response to drought over the past 1500 years in the U.S. Great Plains to tree-ring records of aridity.

What was learned
Forman et al. identified six major aeolian depositional events in the past 1500 years, all but one of which (the 1930s "Dust Bowl" drought) occurred prior to the 20th century. Moving backwards in time from the Dust Bowl, the next three major events occurred during the depths of the Little Ice Age, the next one near the Little Ice Age's inception, and the earliest one near the end of the Dark Ages Cold Period. As for how the earlier droughts compare with those of the past century, the researchers say the 1930s drought (the 20th century's worst depositional event) was less severe than the others, especially the one that has come to be known as the 16th-century megadrought.

What it means
Forman et al. conclude that the aeolian landforms they studied "are clear indicators of climate variability beyond twentieth century norms [our italics], and signify droughts of greater severity and persistence [our italics] than thus far instrumentally recorded." Consequently, their study reveals that post-Little Ice Age warming - which climate alarmists claim to be unprecedented over the past two millennia - has not produced similarly unprecedented droughts. In fact, in the U.S. Great Plains it appears to have done just the opposite.

References
Murray, A.S. and Wintle, A.G. 2000. Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol. Radiation Measurements 32: 57-73.

Woodhouse, C.A. and Overpeck, J.T. 1998. 2000 years of drought variability in the central United States. Bulletin of the American Meteorological Society 79: 2693-2714.