According to Slate.com, we are about to enter the “The United States of Megadrought.” But in much of the central US long-term severe drought has all but disappeared since the 1960s. The trends are all towards less long-term drought, not more.
According to Slate.com, we are about to enter the “The United States of Megadrought.” The article shows the following graphs of historical, current, and projected moisture balances in the Central Plains and Southwest regions (negative numbers indicate dry conditions, with the magnitude indicating the degree of dryness).
Look closely at these plots. First off, both regions were generally drier in the past than over the last several decades. In addition, there appears to be no clear anthropogenic climate change signature in either of these datasets. All we appear to be seeing of late is variability well within the historical record.
Yet the climate modeling efforts suggest we are about to go off the megadrought cliff in the near future. Who knows? Predictions cannot be refuted until they fail to pass. But given the poor performance of climate models to date, we should be very skeptical of any climate modeling projections — and we certainly should not be basing any policy on the models.
Seth Borenstein’s latest article for the Associated Press on this topic is featured at CNS News — which I thought was supposed to be a conservative news outlet, but I guess not. Live and learn.
According to the AP report:
“‘Nearly every year is going to be dry toward the end of the 21st century compared to what we think of as normal conditions now,’ said study lead author Benjamin Cook, a NASA atmospheric scientist. ‘We’re going to have to think about a much drier future in western North America….”
The regions Cook looked at include California, Nevada, Utah, Colorado, New Mexico, Arizona, northern Texas, Oklahoma, Kansas, Nebraska, South Dakota, most of Iowa, southern Minnesota, western Missouri, western Arkansas, and northwestern Louisiana.”
Now there is no doubt that the Southwest is getting drier, regardless of the possible causes and whether or not this is natural variability or some anthropogenic signature. But the Central Plains is a whole different kettle of fish.
The following charts (using data from NOAA’s National Climatic Data Center) show long-term drought (the well-established PDSI index: green=non-drought; yellow=drought; the magnitude of the number indicates the severity of the non-drought or drought conditions) for six of the regions mentioned in the AP article: South Dakota, Oklahoma, Nebraska, northwest Louisiana, Kansas, and Iowa.
Long-term severe drought has all but disappeared in these regions since the 1960s. The trends are all towards less long-term drought, not more. This is in complete contrast to the predictions of the study in question.
Even the drought in northwestern Louisiana over the past decade isn’t nearly as severe as what was experienced during the 1900-1970 period. What makes it seem particularly bad is that it came after the wettest period in recorded history for the region during the 1990s and first half of the 2000s.