More evidence of the naivety of assuming that the 20th century climate record is sufficient to capture the range of variability with which we’ve got to be able to cope. Tian et al in GRL looked at calcite layers in Minnesota lake sediments:
[D]roughts of greater severity and duration than during the 20th century occurred repeatedly, especially prior to 300 AD. Drought variability was anomalously low during the 20th century; ?90% of the variability values during the last 3100 years were greater than the 20th-century average.
And we predicated our settlement patterns and water usage when settling out here in the 18thC on the belief that water regimes were always wet.
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