Journey To The Desert's Edge, Part 11
Note:
this is the eleventh in a series of occasionally appearing entries focusing on
deserts in general and the drylands of West Texas in particular
“One
reason that Texas is so drought prone is its latitude, the same latitude as the
Sahara Desert. As in the Sahara, large
high-pressure cells can sit over the state for weeks or months at a time and
block storms and incoming moisture. The
cause of these cells is not well understood but possible influences are solar
storm cycles, ocean temperature cycles (El Nino and La Nina), and global
warming.”-- Andrew Sansom, Water In Texas: An Introduction, 2008
Men’s lives in a place have always been
influenced by climate: a truth...
For centuries, the western Concho Valley of
Texas has been a sparsely land due to its harsh and demanding climate. When the Spanish explored the area in the
1600s, they found people we know today as the Jumanos, some of whom lived in
small rancherias along the river and some of whom practiced a more nomadic
lifestyle. By the latter half of the
Seventeenth Century, the Jumanos found themselves displaced by the Lipan Apache
who for a time, controlled barren lands between the Colorado River of Texas and
the Rio Grande. Next came the Comanche...
The concept of large permanent settlements came
fairly late to this land of short grass and cactus. It wasn’t until 1870 that a thousand people
lived in what is now present day Tom Green County and most of those made their
homes near Fort Concho, one of several remote military outposts established
after the Civil War to bring law and order to western Texas...
 |
| The Lipan Apache, seen here in a painting by George Nelson, changed their lifestyle after the introduction of the horse and abandoned the traditional wikiup dwelling in favor of the tipis favored by Plains tribes |
Uncertainty is the name of the game when it
comes to knowing what happens tomorrow (or even later today): a second truth...
As a consequence, astrologers and other folks
with prognostication skills in fields like tea-leaf analysis and sheep entrail
reading have enjoyed steady employment for millenia. The problem is that accurate predictions
based on planetary locations one day are usually followed by multiple weeks of
being wrong. It’s a flaw that encourages
skepticism among scientists who tend to believe theories should be considered
faulty if reality disproves predictions based upon those theories...
 |
Man's attempt to foresee changes in
weather dates at least to the days
of the ancient Babylonians
|
Science really doesn’t like uncertainty but
efforts by scientists to provide us with a clear picture of Earth’s future
climate is no easy task. This difficulty
may offer some comfort to those who prefer to ignore the overwhelming evidence
of global warming. But the facts do not
take the side of climate ostriches who believe that we’re merely having a
couple warm years before things go back to normal. Sea levels are rising, Arctic ice levels are
decreasing, lower troposphere temperatures are
increasing...
Where global warming leads the United States in
terms of long term effects is a mixed bag.
Models show average daily temperatures will continue to rise but will do
so unevenly both in terms of time and location.
Frost free times of the year and growing seasons will lengthen,
especially in the western half of the United States. Projections for precipitation are that it can
be expected to increase in the winter and spring in the north. But the rains and snow are likely to decrease
in the Southwest during those seasons as well.
Heat waves will be more common everywhere with periods of drought
lasting longer in the already arid Southwest.
For those who dislike frozen winter days, there is the promise that cold
waves are likely to become less intense over time. Those who live along the coasts can expect
sea levels to rise and for hurricanes to become stronger and more dangerous...
A good deal of global warming can be tied to an
increase in greenhouse gases (which include water vapor, carbon dioxide,
methane, nitrous oxide, and ozone) in the atmosphere. Greenhouse gases absorb and emit radiation in
the thermal infrared range. This is not
necessarily bad-- the radiation from greenhouse gases in the atmosphere raise a
planet’s surface temperature to a level above what it would be if the planet
had no atmosphere. Without an
atmosphere, Earth’s surface temperature would likely be about 0 degrees
Fahrenheit...
 |
West Texas sheep rancher as depicted in a mural
by Stylle Read
|
But too much atmospheric warming is not a good
thing. Our planetary neighbor Venus
enjoys mean surface temperatures of about 863 degrees Fahrenheit thanks to the
greenhouse effect and an atmosphere which is roughly 96% carbon dioxide...
Overwhelming numbers of scientists believe
human activity, particularly human activity increasing the amount of greenhouse
gases in the atmosphere, is a major factor in the global warming now taking
place. Lest the reader be tempted to
believe this assertion is a new-fangled notion fostered by enemies of the
energy companies, we note Alexander Graham Bell expressed concern in 1917 with our
continued fossil-fuel use as ultimately causing a terrestrial “hot house
effect” versus a “greenhouse effect”...
The level of carbon dioxide emissions generated
by human activity is particularly critical in understanding future climate on
earth. Studies of ice core samples
reveal a carbon dioxide concentration of about 270 parts per million (ppm) in
the years immediately before the Industrial Revolution. By 1960, the level had increased to 313
ppm. By 2013, carbon dioxide
concentrations were at 400 ppm. This
rapidly rising number (and attendant global warming) can be traced primarily to
human activities such as burning fossil fuels and tropical deforestation...
Global warming travels with problems for humans,
the species largely responsible, for it and the severity of future climate
changes it brings may be in the hands of those same humans. In terms of the effects we noted earlier, we
might point out rising sea levels impact the habitability of coastlines. Likewise, higher temperatures and the
likelihood of increased precipitation in some areas and prolonged drought in
others affect agricultural production...
Dire predictions for the future of the planet
as a whole set aside, we all have a localized interest in what changing weather
brings. What does global warming mean
for me, I ask...
My home is a semi-arid area at the edge of the
Chihuahuan Desert with an average annual rainfall of about 20 inches. This average, however, may not entirely what
it would be if man let Mother Nature take her own course. For roughly two decades, cloud seeding operations
have been used to enhance area rainfall.
A study conducted for the city of San Angelo suggests rainfall during
the 1985-1989 period increased at least 25% in seeded areas during the months seeding
operations took place...
 |
| Ranchland in the western Concho Valley |
What effect cloud seeding ultimately will have
on area rainfall averages remains to be seen.
In the fifty years prior to consistent cloud seeding, San Angelo
averaged 19.08 inches of precipitation per year with individual years totaling
as low as 7.41 inches and as high as 40.40 inches. Since folks began injecting cumulus clouds
with silver iodide, annual average rainfall has increased to 21.58 inches with
individual year extremes ranging from 9.21 to 32.93 inches...
(Compounding the difficulty of short-term
assessments of long-term climate change as it occurs in the Concho Valley is
the fact precipitation in the dry country is erratic. While a given year’s rain in semi-arid
regions is usually within ± 50% of the statistical average, there is no
guarantee amounts that actually fall will be in that range. Additionally, the monthly deviation from
statistical norms can be (and usually are) significant. The month of May offers a good example. With an annual average rainfall of 02.82
inches, May sits statistically as the “wettest month of the year” for San
Angelo. But actual monthly totals from
2005 to 2016 range from 0.12 inches to 9.12 inches.)
 |
Alexander Graham Bell, father of the
telephone and prophet of global warming
|
Although cloud seeding likely helps raise
reservoir levels, it makes analyzing effects of global warming on natural precipitation
patterns and evaporation rates in this sector of Texas more difficult. This is dry country by nature-- we can look at data collected by the Texas
A&M agricultural research station near San Angelo over a 54 year period and
see the site’s 19.20 inches of precipitation was offset by a potential
evapotranspiration rate of 71.34 inches.
Any increase in average annual rainfall derived from either cloud
seeding or precipitation pattern changes induced by global warming may not
prove to be as useful as hoped if rising temperatures lead to higher
evaporation rates...
Scientists suspect rainfall may gradually
lessen in already arid South and West Texas.
As temperatures continue to rise and warm air blankets the state for
longer periods of time, meeting points between cold and warm air masses will
shift and push seasonal rains more to the north and east...
Probably a lot of long hot summer days for my
part of the world down the road...
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CREDITS
Note: All
photographs and information for this essay were located through Google Images, Wikipedia
and readily available general information sources such as Enclcopedia
Brittanica, without authoritative source or ownership information except as
noted: photographs of Stylle Read mural and Concho Valley ranchland by Louis R Nugent; George Nelson Lipan Apache painting from http://www.forttumbleweed.net/apachepass.html
; water supply sustainability from https://data.globalchange.gov/assets/36/96/d21cee93238d81f9ea1404f06c5d/ECO_water_risk_index_V2.png;
average Texas summer temperature increase from http://images1.dallasobserver.com/imager/u/745xauto/7439644/climatemaps.jpg
; Alexander Graham Bell photograph from http://www.telcomhistory.org/vm/Images/AGB1867.jpg
; Information on general effects of
climate change from http://climate.nasa.gov/effects/; the Future of Climate Change from https://www.epa.gov/climate-change-science/future-climate-change; evidence for global warming from https://www.skepticalscience.com/evidence-for-global-warming.htm; rainfall increase from cloud seeding from https://www.tdlr.texas.gov/weather/weatherfaq.htm; nature of semi-arid precipitation patterns from http://www.fao.org/docrep/t0122e/t0122e03.htm; future rainfalls likely more to north and east from https://www.texastribune.org/2014/07/14/state-only-planning-bigger-texas-not-hotter-one/
