A representation of the summer moisture in the US Central Plains and Southwest is shown. The brown line represents the variation in dryness since the year 1000; the lower the line on the graph, the drier the conditions. Colored lines to the right side of the graph represent what climate models see ahead: a trend toward dryness not seen in the previous millennium. As the authors describe it: Regional average time series of the summer season moisture balance metrics from the NADA and CMIP5models.The observational NADA PDSI series (brown) is smoothed using a 50-year loess spline to emphasize the low-frequency variability in the paleo-record. Model time series (PDSI, SM-30cm, and SM-2m) are the multimodel means averaged across the 17 CMIP5models, and the gray shaded area is the multimodel interquartile range for model PDSI.