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A History of Columbia River Basin Droughts Since 1750
Gedalof, Z., Peterson, D.L. and Mantua, N.J.  2004.  Columbia River flow and drought since 1750.  Journal of the American Water Resources Association 40: 1579-1592.

What was done
A network of 32 drought-sensitive tree-ring chronologies was used to reconstruct mean water-year flow on the Columbia River at The Dales, Oregon, USA, since 1750.  This study of the second largest drainage basin in the United States is stated by the authors to have been done "for the purpose of assessing the representativeness of recent observations, especially with respect to low frequency changes and extreme events."

What was learned
Gedalof et al. report that "low pass filtering the flow record suggests that persistent low flows during the 1840s were probably the most severe of the past 250 years," and that "the drought of the 1930s is probably the second most severe."  More recent droughts, in their words, "have led to conflicts among uses (e.g., hydroelectric production versus protecting salmon runs), increased costs to end users (notably municipal power users), and in some cases the total loss of access to water (in particular junior water rights holders in the agricultural sector)."  Nevertheless, they say "these recent droughts were not exceptional in the context of the last 250 years and were of shorter duration than many past events."

What it means
Climate alarmists typically claim that CO2-induced global warming will be accompanied by more frequent and severe droughts and floods, as they claim that earth's climate will become less stable with increasing warmth.  In this study of a period of time that takes us from the depths of the Little Ice Age to the peak of what CO2 detesters vehemently claim was the warmest period of the past two millennia, however, we see nothing of the sort.  In fact, droughts were considerably worse in the early much colder part of the record; and Gedalof et al. report that "the period from 1950 to 1987 is anomalous in the context of this record for having no notable multiyear drought events."

It is clear from these facts that the past could well repeat itself, without any help from rising temperatures and with far more disastrous consequences.  Gedalof et al. rightly note, for example, that the drought of the 1930s, the second-worst of the record, "should not be regarded as an anomalous event, but is likely a typical fluctuation of the Columbia River system."  Hence, they conclude with some appropriately somber words: "the basin has been fully exploited in terms of storage capacity, the demands posed on the system continue to increase, availability is likely to diminish, and the potential for multiyear droughts has probably been underestimated."  All of these problems have absolutely nothing to do with either rising atmospheric CO2 concentrations or temperatures; and none of them will be solved by pretending we can change the course of earth's climatic trajectory, whatever it happens to be.

Reviewed 4 May 2005