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Droughts of Southwestern North America: Past and Present
Volume 14, Number 41: 12 October 2011

The world's climate alarmists claim that rising temperatures will bring ever worse droughts to precipitation-deficient regions of the earth. One such region is Southwest North America, for which Woodhouse et al. (2010) developed a 1200-year history of drought that allowed them to compare recent droughts with those of prior centuries; and in spite of the fact that the warmth of the last few decades is said by alarmists to have been unprecedented over the past millennium or more, the review and analysis presented by the five U.S. researchers demonstrates that major 20th century droughts "pale in comparison to droughts documented in paleoclimatic records over the past two millennia (Cook et al., 2009)," which suggests that recent temperatures have not been unprecedented.

Presenting a little more detail, Woodhouse et al. report that "the medieval period, ~AD 900-1300," was "a period of extensive and persistent aridity over western North America," with paleoclimatic evidence suggesting that drought in the mid-12th century (AD 1146-1155) "far exceeded the severity, duration, and extent of subsequent droughts," including the 21st century drought of 2000-2009; and they also state that the AD 1146-1155 period was "anomalously warm," which would seem to confirm the climate-alarmist contention that greater warmth leads to greater droughts. However, the five scientists contend that temperature was "almost certainly higher during the 21st century drought," which again contradicts the climate-alarmist claim that greater warmth translates into greater drought in precipitation-deficient regions of the earth.

These observations do little to advance the climate-alarmist cause; for in order for their claim that rising temperatures promote more severe and expansive droughts to be correct, the peak warmth of the Medieval Warm Period would have had to have been greater than the Current Warm Period has been to date; but that situation is in conflict with their even more basic claim that recent temperatures have been unprecedented compared to those of the prior millennium or two.

Sherwood, Keith and Craig Idso

References
Cook, E.R., Seager, R., Heim Jr., R.R., Vose, R.S., Herweijer, C. and Woodhouse, C. 2009. Megadroughts in North America: Placing IPCC projections of hydroclimatic change in a long-term paleoclimate context. Journal of Quaternary Science 25: 48-61.

Woodhouse, C.A., Meko, D.M., MacDonald, G.M., Stahle, D.W. and Cook, E.R. 2010. A 1,200-year perspective of 21st century drought in southwestern North America. Proceedings of the National Academy of Sciences USA 107: 21,283-21,288.