What was done
The authors developed a Holocene history of flood magnitudes in the northern Uinta Mountains of northeastern Utah from reconstructed cross-sectional areas of abandoned channels and relationships relating channel cross-sections to flood magnitudes derived from modern stream gage and channel records.

What was learned
Of most interest to us, Carson et al. report that over the past 5,000 years, the record of bankfull discharge "corresponds well with independent paleoclimate data for the Uinta Mountains," and that "during this period, the magnitude of the modal flood is smaller than modern during warm dry intervals and greater than modern during cool wet intervals," noting most particularly that "the decrease in flood magnitudes following 1000 cal yr B.P. corresponds to numerous local and regional records of warming during the Medieval Climatic Anomaly."

Based upon the three researchers' graphical results, the three largest negative departures from modern bankfull flood magnitudes (indicating greater than modern warmth) range from approximately 15-22%, as best we can determine from visual inspection of their plotted data; and they occur between about 750 and 600 cal yr B.P., as determined from radiocarbon dating of basal channel-fill sediments.

What it means
In addition to demonstrating that the degree of natural variability in northeastern Utah flood magnitudes throughout the Holocene has been much larger (in both positive and negative directions) than what has been observed in modern times (which demonstrates that possible future occurrences of greater- or smaller-than-modern floods in the region ought not be regarded as "unprecedented," as climate alarmists are typically prone to claim), Carson et al.'s findings demonstrate that the portion of the Medieval Warm Period between about AD 1250 and 1400 was likely significantly warmer than it is at present (which demonstrates that since something other than high concentrations of atmospheric CO2 was responsible for the region's earlier greater-than-present warmth, one need not invoke today's much higher CO2 concentrations as the reason for our actually lower current temperatures).