A Drought of Truth

August 24, 1999 • Commentary

Make no mistake about it: It is very dry in the Mid‐​Atlantic region. Farmers in Virginia’s Shenandoah Valley and much of Maryland are coping with a very difficult situation; residents of highly populated Northern Virginia are nearly as dry but suffer few effects, thanks to upstream reservoirs and the very wide Potomac River. Some might be happy to not have to water the lawn.

The real story of the drought of 1999 is the phenomenal level of distortion that has been heaped on by the White House and by the large number of reporters who care more for sensation than truth. President Clinton wants to mix the drought up with global warming and food scares. After calling the situation the “worst agricultural drought this century,” he added on August 7: “As weather disruptions become even more common, and they will, they will demand a more coordinated response by the national government.”

Those who know Clinton/​Gore may suspect a little bit of exaggeration here. So how bad is it? In terms of severity and extent, this drought is nothing special. Climatologists measure drought with something called the Palmer Drought Severity Index, a clunky mathematical beast that attempts to account for all of the variables that define moisture status: rainfall, evaporation, runoff (into streams) and ground storage.

It has some quirks, including the debatable notion that drought is measured primarily by the departure from average moisture at any spot. In other words, if a place like Washington, D.C., receives 60 percent of its average rainfall for a year — which is the current situation — it’s likely to be in a big time drought, even though it still gets 13 times the average rainfall of Death Valley, which is not in a drought as long as it stays near its annual average rainfall of 1.89 inches.

There’s a certain sort of liberal logic around this. The implication is that the natural vegetation as well as the human infrastructure put in its place are adapted to “normal” conditions for that spot, and the more abnormal things become, the more they fall apart. In other words, Death Valley Scotty is adapted to Death Valley and Al Gore is adapted to Washington, but if either experiences below normal rainfall, he’ll be unhappy.

To make everyone’s moisture shortages equivalent, the Palmer Index is statistically adjusted to give uniform values between places. It is assigned an average value of zero and a “standard deviation” of 2.0. This is a measure of the scatter of month‐​to‐​month readings about the arbitrary average of zero. Statistically speaking, one‐​sixth of the time we are more than one standard deviation below the average. Federal climatologists give this zone a name: All values between -2 and -3 in the Palmer Index are called “Moderate Drought.”

Think about it. On average, any given place has a “moderate drought” one‐​sixth of the time. Flipping the data around, this statistical technique also means that, on average, one‐​sixth (17 percent) of the nation is in “Moderate Drought.”

That makes for some pretty snappy electioneering and porking. It gets pretty easy for some climate demagogue to stand in front of voters in states with a lot of electoral votes, claiming that this is what you get from mean ole Republicans who don’t want to stop global warming. That’s pretty much what Al Gore pulled last week, in a lecture along with Bill Nye, the public broadcasting (surprised?) science guy.

But in fairness, Northern Virginia, where this spectacle unfolded, is in “Extreme Drought.” That occurs when the Palmer Index is more than two standard deviations away from its mean; that is, has a value below -4.0.

Statistically speaking, this occurs on average 2.5 percent of the time at your house, or in an average year over 2.5 percent of the nation. That’s right — thanks to the wonders of statistical fiddling, an area the size of several small states is normally in “Extreme Drought.” To me, the notion of “extreme drought” conjures up visions of cattle skulls and dust storms, something I can’t seem to find outside my Shenandoah Valley window. Perhaps the rhetoric is a bit hot.

The most recent Palmer Index figures, from August 7, are very interesting. It’s below -4.0 in Northern Virginia, much of Maryland and Delaware, the Mohawk Valley in New York, a little spot in Central Florida and two places in the desert region of the Northwest that probably can’t tell the difference between hardly any average rain and a bit less.

Together, these regions comprise 1.98 percent of this fair country. But, on average, 2.5 percent of the nation has “Extreme Drought.” That’s right. For all of the lead stories, for all of the hype and demagoguery, less of the nation than average is currently experiencing a major drought. It also hasn’t hurt the hype machine that the epicenter of dryness just happens to be Washington, D.C. That makes this more important than any moisture shortage in the world.

The same thing happens when there’s a big snowstorm here. Twenty‐​four inches of snow in D.C. in January 1996 prompted a Newsweek cover article with the headline, “Blizzards, floods and hurricanes: blame global warming.” The red band said “Hillary’s Damage Control,” doubly emphasizing the apparently limited number of constantly recycled news stories.

The current situation doesn’t mean that conditions aren’t pretty bad down on the Mid‐​Atlantic farm. Those people need a hand. But it also means that any attempt to hype this thing into something that it isn’t — some type of national or global catastrophe — is a clear and cynical attempt at distortion.

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