Paper Reviewed
Ho, M., Lall, U. and Cook, E.R. 2016. Can a paleodrought record be used to reconstruct streamflow?: A case study for the Missouri River Basin. Water Resources Research 52: 5195-5212.

Proxy records of streamflow are important because they can provide a clearer view of the range of natural variability beyond that seen in historical or observational records. Recognizing and understanding that natural variability is key to both making and evaluating future streamflow predictions. And in this light, the recent study of Ho et al. (2016) is a welcomed work for its reconstruction of streamflow in the Missouri River Basin (MRB) over the past five centuries.

Using monthly streamflow data obtained from the U.S. Geological Survey, which the team of three researchers correlated with a 0.5° x 0.5° latitude/longitude gridded paleoclimate reconstruction of summer Palmer Drought Severity Index based on a network of tree-ring chronologies, Ho et al. performed a series of statistical tests and analyses to reconstruct mean annual streamflow in the MRB over the period 1473 to 2005. And what did this reconstruction reveal?

Results indicated periods of drought in the 1540s, 1590s and 1750s that were "of similar or greater magnitude than the streamflow deficits associated with the Civil War, Dust Bowl, or 1950s drought," which latter historical events Ho et al. say "had wide ranging impacts on ecological states, agricultural produce, and social activities and are often used as benchmark droughts to which contemporary droughts are compared." Similarly, the authors report that the reconstructed record also shows "several periods where annual flows are larger than the maximum instrumental streamflow," including anomalously high values in the 1490s and 1560s.

In light of the above findings, Ho et al. conclude that "the maximum persistence of drought and floods over the past 500 years far exceeds those observed in the instrumental record." And that is an important conclusion, for it reveals there has been no identifiable influence of rising CO2 and/or temperature on historic streamflow anomalies (i.e., floods or droughts) in the MRB. And that, in turn, represents yet another nail in the coffin of the climate-alarmist claim that CO2-induced global warming is causing more extreme and frequent droughts and floods.