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Temperature Pattern Indicates Texas High Plains Becoming Warmer

May 14, 2014

CONTACT:    Dr. B. A. “Bob” Stewart, 806-651-2299, bstewart@wtamu.edu

Temperature Pattern Indicates Texas High Plains Becoming Warmer

CANYON, Texas—The Texas High Plains is experiencing a serious drought but a local agriculture researcher says that increasing temperatures may be more pronounced than the decreasing precipitation. This, in turn, could require some changes for agriculture in the area, according to Dr. B.A. “Bob” Stewart, who for the past 20 years has served as director of the Dryland Agriculture Institute at West Texas A&M University and before that served as director of the USDA Conservation and Production Laboratory at Bushland for 25 years.

Stewart analyzed precipitation and temperature data from 1895-2013 for the Texas High Plains. The graph shows five-year moving averages for precipitation and temperature values from 1895 through 2013. The trend lines indicate that the area has become significantly warmer with slightly less precipitation. The precipitation pattern for the Texas High Plains is directly opposite to the temperature pattern.

Graph showing the increase in tempurature and decrease in precipitation

(Stewart's graph depicts the five-year moving average annual temperature and precipitation values from 1895-2013 for the Texas High Plains Climate Division as determined by the National Oceanic and Atmospheric Administration.)

While it is expected that temperatures would be lower during wet years and higher during dry years, the significant and continuing increase in temperatures strongly suggests that temperature is the main driver. The two most noted dry periods in the Texas High Plains are the Dust Bowl years of the 1930s, and the 1950 to 1956 period that was even drier than the 1930s. The air temperatures increased dramatically during those dry periods but dropped afterwards and precipitation increased. Since about 1980, the average temperatures have mostly increased and are higher today than during either of the historic dry periods suggesting the downward trend of precipitation in the Texas High Plains is likely due to increasing temperatures.

The conversion of grassland to cropland began in the Texas High Plains in the late 1800s during a cool and wet period and peaked in the 1920s. Since that favorable beginning, the average precipitation values have trended downward about one inch while the average temperatures have trended upward almost two degrees farenheit. The temperature rise has been two times greater from October through March than from April through September.

Stewart said a so called “rule of thumb” for the High Plains has been that the average precipitation multiplied by two approximates the highest amount for a year, and the average divided by two approximates the lowest. Since about 1960, this has not been applicable. The high rainfall years have only been about 25 percent above average and the dry years have been as low as 30 percent of average or lower. Although there will continue to be wet and dry years in the High Plains, “the wet years may not be as wet and the dry years may be drier if temperatures continue to increase,” Stewart said.

Historically, precipitation has supplied as much as 50 percent of the water for area irrigated crops. Less precipitation, higher temperatures and a declining Ogallala Aquifer water supply will put additional strains on irrigated crops.  

Dryland agriculture has always been challenging in the area and increasing temperatures coupled with decreasing precipitation may result in shifts in cropping systems. Increasing temperatures in areas of limited water exacerbates the situation because more units of water are required to produce a unit of dry matter.

Stewart said his analysis is not to forecast gloom and doom for the area but to suggest changes will be required. Since the Dust Bowl, the area has focused on changing the environment, primarily with irrigation. Now, “with irrigation declining and temperatures increasing, the emphasis must shift to adapting to the environment,” he said. Some cropland may revert to grassland, and some grain production may shift to forage production. Urban practices may also need to change by utilizing grasses and landscaping that require less water.

People often wonder if the area will experience another Dust Bowl. Stewart has answered that question countless times throughout his career, and his answer has always been and remains “No,” but he is becoming more cautious with his reasons. “Even though the weather conditions may become as bad or even worse, there are several million acres of cropland during the 1930s that are now in grass, and several million irrigated acres today compared to almost none during the Dust Bowl. This, coupled with farmers having better equipment and more knowledge, will prevent dust storms of the magnitude of those during the Dust Bowl,” he said.

It is critical that we monitor the changes, anticipate their effects and take whatever steps are required for adaptation, Stewart said. The drought that is being experienced today is likely more than just a drought. Until and unless there is a downward turn in the temperatures, the return to precipitation amounts received during the ‘good old days’ may not occur.
    
 

—WTAMU—


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John Zhu
on 5.21.2014

Dr. Steward, Do you think your research is applicable to the area of Wichita Falls? Thanks, John Zhu, Ph.D. Hydrologist TWDB