Prior to 1948 the standard deviation of June-August precipitation was 4.9 inches. Since 1948 it has been 3.6 inches. Their theory falls flat on its face. And the wettest year and the driest year were both prior to 1948.
Duke has three strikes so far. But the real problem is their choice of 1948 as the start date of the study. The first couple of decades after 1948 had low variability, as you can see in the graph. Did they cherry pick the start date, or did they just get really unlucky?
Whatever the cause, their claim fails. Summer precipitation was more variable from 1895-1948 than it has been since. Why wasn’t this caught in peer-review? It took me five minutes to see the problem.