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Droughts of the Central and Southern Rocky Mountains
Gray, S.T., Betancourt, J.L., Fastie, C.L. and Jackson, S.T.  2003.  Patterns and sources of multidecadal oscillations in drought-sensitive tree-ring records from the central and southern Rocky Mountains.  Geophysical Research Letters 30: 10.1029/2002GL016154.

What was done
The authors examined fifteen tree ring-width series that have been used in previous reconstructions of drought for evidence of low-frequency variation in precipitation in five regional composite chronologies pertaining to the central and southern Rocky Mountains.

What was learned
In the words of the authors, "strong multidecadal phasing of moisture variation was present in all regions during the late 16th century megadrought," and "oscillatory modes in the 30-70 year domain persisted until the mid-19th century in two regions, and wet-dry cycles were apparently synchronous at some sites until the 1950s drought."  They also note that "severe drought conditions across consecutive seasons and years in the central and southern Rockies may ensue from coupling of the cold phase PDO [Pacific Decadal Oscillation] with the warm phase AMO [Atlantic Multidecadal Oscillation] (Cayan et al., 1998; Barlow et al., 2001; Enfield et al., 2001)," something they envision happening in both the severe 1950s drought and the late 16th century megadrought.

What it means
Severe drought is no stranger to the central and southern Rocky Mountains of North America.  Episodes of extreme dryness are naturally recurring products of various climate "regime shifts" in the Pacific and Atlantic Oceans.  There is, therefore, no compelling reason to associate any such drought of the present or future with global warming, as climate alarmists are readily inclined to do, having stated publicly in many venues that increases in both floods and droughts can be expected to accompany CO2-induced increases in global temperature.

Barlow, M., Nigam, S. and Berberry, E.H.  2001.  ENSO, Pacific decadal variability, and U.S. summertime precipitation, drought and streamflow.  Journal of Climate 14: 2105-2128.

Cayan, D.R., Dettinger, M.D., Diaz, H.F. and Graham, N.E.  1998.  Decadal variability of precipitation over western North America.  Journal of Climate 11: 3148-3166.

Enfield, D.B., Mestas-Nuņez, A.M. and Trimble, P.J.  2001.  The Atlantic multidecadal oscillation and its relation to rainfall and river flows in the continental U.S.  Geophysical Research Letters 28: 277-280.

Reviewed 10 September 2003