Nile gauge records of variations in Nile floods from the 9th century to the 15th century AD reveal pronounced episodes of low Nile and high Nile flood discharge. Historical data reveal that this period was also characterized by the worst known famines on record. Exploratory comparisons of variations in Nile flood discharge with high-resolution data on sea surface temperature of the North Atlantic climate from three case studies suggest that rainfall at the source of the Nile was influenced by the North Atlantic Oscillation. However, there are apparently flip-flop reversals from periods when variations in Nile flood discharge are positively related to North Atlantic warming to periods where the opposite takes place. The key transitions occur at~AD 900, 1010, 1070, 1180, 1350 and 1400. The putative flip-flop junctures, which require further confirmation, appear to be quite rapid and some seem to have had dramatic effects on Nile flood discharge, especially if they recurred at short intervals, characteristic of the period from the 9th to the 14th century, coincident with the so-called Medieval Warm Period. The transition from one state to the other was characterized by incidents of low, high or a succession of both low and high extreme floods. The cluster of extreme floods was detrimental causing famines and economic disasters that are unmatched over the last 2000 years.
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