As everyone should by now be well aware, this season’s heat wave (in the summertime, no less!) is the product of the earth’s climate failing to keep itself pleasantly cool, straining as it is under mountains of carbon dioxide emitted by human beings.   Amid the gloom of consequences implied by an earth in which vast swaths of land do not become locked in glaciation, there is some cheer.  The heat is buckling roads all over the Northeast and Midwest of the US, causing demand to surge for civil engineers who know how to build roads that won’t crumple and buckle under the sun.

Southern civil engineers are used to the heat.  A summertime below the Mason-Dixon line where the mercury doesn’t hit a hundred is a blessed event.  I think it’s happened about a half dozen times in my hometown of Birmingham, AL during my lifetime.  This year ain’t one of ’em.

The roads in the South never crumple and buckle because of the heat.  This picture is of a road in Chicago that buckled to impassability with the heat wave, one of many pictures I’ve seen of roads in the Midwest and Northeast drawing up like this:

If Chicago gets to a hundred today (July 6, 2012), as is its forecast, and as it has over the last two days, that will make four whole days this year when temps have exceeded a hundred degrees (102 being the highest).  Four consecutive days (though Chicago’s haven’t been consecutive) of barely breaking a hundred degrees hardly even registers as a heat wave in the summer in Alabama.  In 2007, temps exceeded a hundred degrees for practically the whole of July and August.  Still, none of the roads buckled.  Maybe Yankee engineering ain’t all its cracked up to be (no pun intended). 

Hot weather is usually also dry weather.  When it’s really hot down here in the old Confederacy, like 105 or so, it almost goes without saying that there ain’t been no rain.  Just ask the folks in Texas, whose memory is still fresh of last summer’s miserable weather, about the correlation between heat and drought.  Scattered thunderstorms supply the occasional relief (last night for my locale), but when the air is hot, the thunderstorms are more sparsely scattered. 

But does it change the amount of rain that hasn’t fallen if the government declares that an area is in a drought?

The headlines today are that 56% of continental US are in drought.  Here’s the chart:

US Drought Monitor, July 3, 2012

But designating a place as being in a “drought” is meaningless without defining the term.   And the US Drought Monitor really doesn’t define the term.  It is clearly the case that some sort of measurement is taken against historical average precipitation rates to delineate areas that are or aren’t in drought.  But historical averages are just that–averages–that may or may not reflect what actually happens on the ground.  A place that got 50 inches of rain per year for five years, followed by none at all for five years, would have average rainfall for the decade of 25 inches per year.  If the 25 inches per years is then internalized as the amount of rainfall that is to be expected, every single subsequent year in which the previous pattern is repeated would be enduring either a deluge or a drought.  Historical averages are not the “norm” as you so often hear from the weatherman.  You can drown in six feet of water in a lake whose “normal”, i.e., average depth, is six inches.

The US Drought Monitor is published once a week by the US Department of Agriculture.  But “droughts” are not weekly things.  My dictionary defines drought as a long period of abnormally low rainfall, especially one that adversely affects growing or living conditions.  However long the “long period” is imagined to be, it can’t be so short as a week.  Comparing rainfall against a weekly historical average is utterly meaningless.  Frontal systems bringing rain take longer than a week just to traverse the continent.  Here’s what the Drought Monitor says about its map:

The U.S. Drought Monitor is unique, blending numeric measures of drought and experts’ best judgment into a single map every week. It started in 1999 as a federal, state, and academic partnership, growing out of a Western Governors’ Association initiative to provide timely and understandable scientific information on water supply and drought for policymakers.

The Monitor is produced by a rotating group of authors from the U.S. Department of Agriculture, the National Oceanic and Atmospheric Administration, and the National Drought Mitigation Center. It incorporates review from a group of 250 climatologists, extension agents, and others across the nation…

In other words, “drought” means whatever a rotating group of specialists decide means.  Yet it’s surely the case that the US Department of Agriculture didn’t devise the Drought Monitor in order to write headlines and garner attention for itself when conditions got hot and dry.  Drought is a real thing, not a human perception contrived by a government agency seeking headlines, therefore it is completely real this week that 56% of the continental US is under drought conditions. 

Drought, even by the dictionary definition, is a relative matter, a comparison of the actual rainfall against what is expected based on historical averages.  The worst drought in all the hundred or so years of recorded history in Central Alabama occurred in 2007, when annual rainfall was barely half its “normal” amount.  Birmingham that year got 30 inches of rain, whereas the historical average is about 55.  Thirty inches of rain in a year is roughly what rainy Seattle historically averages.  Yet you would have thought Birmingham had become a desert in the span of a year to hear the local weather authorities describe things.  All things are relative, but the notion of drought is exceptionally so. 

Central Alabama is again considered to be in “drought” by the Monitor.  About 22 inches out of a historical average by this time of the year of roughly 28 inches has fallen.  20% shy of the average is a drought?   Like everything else, words gradually lose value over time and usage.  Every problem is now a crisis.  Every social movement is now a war.  Every hot dry spell is now a drought.   When a real drought hits, the meteorologists will have to come up with a new word to describe it, since they’ve already cheapened the word “drought” to mean so much until it means nothing at all.  It shouldn’t present much of a challenge for the carny-barkers that report the weather these days.  They adopted a new word “derecho” in short order when it became clear that “severe thunderstorm” had been so overused until it had lost its punch.   The new word for drought should be of similarly obscure, foreign-sounding origins.  It’s far more palatable to have relatively rare (in human lifetimes) weather calamities be of obscure, foreign-sounding origins, because then you have someone to subconsciously blame (them damn foreigners) against whom forces might possibly even be deployed, in the same manner that all other imperial problems are resolved.

In the meantime, as the heat buckles the infrastructure up North, demand surges for civil engineers from the South who know how to build roads capable of withstanding hundred degree heat.