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A 500-Year History of Drought in the Pacific Northwest, USA
Knapp, P.A., Grissino-Mayer, H.D. and Soule, P.T.  2002.  Climatic regionalization and the spatio-temporal occurrence of extreme single-year drought events (1500-1998) in the interior Pacific Northwest, USA.  Quaternary Research 58: 226-233.

Climate alarmists claim that earth will experience all sorts of extreme weather as the planet warms; and they claim that the warming of the last century was "unprecedented over the past millennium."  Hence, the 500-year record of severe single-year Pacific Northwest (USA) droughts developed in this study provides a good database for assessing the validity of these claims with respect to this particular phenomenon in this particular part of the world.

What was done
Eighteen western juniper (Juniperus occidentalis var. occidentalis Hook.) tree-ring chronologies from the Pacific Northwest of the United States were used to identify extreme Climatic Pointer Years (CPYs) -- indicative of severe single-year droughts -- over the period 1500-1998.

What was learned
In the words of the authors, "widespread and extreme CPYs were concentrated in the 16th and early part of the 17th centuries," while "both the 18th and 19th centuries were largely characterized by a paucity of drought events that were severe and widespread."  Thereafter, however, "CPYs became more numerous during the 20th century," although the number of 20th century extreme CPYs (26) was still substantially less than the mean of the number of 16th and 17th century extreme CPYs (38).

What it means
The data of this study fail to support the climate-alarmist claim that global warming increases the frequency of severe droughts.  Although this study relates to only one type of extreme weather in one part of the world, it joins a growing number of other such studies from all around the globe that fail to reveal the type of meteorological behavior predicted by climate alarmists [see Extreme Weather in our Subject Index].  Hence, since the planet has indeed warmed over the past century, although not to the "unprecedented" degree claimed by climate alarmists, it is getting more and more difficult for them to continue to claim that global warming will lead to more extreme weather events of all types.  Nevertheless, they still make such claims, apparently hoping that people will not learn of the tremendous body of evidence that argues against them.

Reviewed 12 February 2003