By Carroll Wilson – Published January 13, 2008
TELEGRAM MANAGING EDITOR

Daily high temperatures are dropping in Temple, and daily lows are rising, according to numbers crunched by a senior research scientist here.

Dr. Jimmy Williams of the Blackland Research Center pulled the data out of weather information he’s compiled from the last 95 years.

“I’ve been in touch with a colleague in Maryland – they’re experts in climate change – and he concluded the same thing we did,” Williams said.

Over the last nearly 100 years, the daily highs have dropped roughly 4 degrees Fahrenheit and daily lows have risen by about the same amount, according to Williams’ data.

Williams said the trend might or might not continue.

He said, though, he never foresees a time when the highs and lows will converge.

“If we’re getting warmer minimum temps, we could see a longer growing season,” Williams said. “The cooler maxes may be better for the summer crops.”

Regardless, he said, the fluctuations should have no real effect on corn, the top crop in this part of Texas.

Dr. Jim Kiniry, a fellow researcher at the Grassland Soil and Water Research lab, said if one variety of corn reacts strongly to climate change, farmers can simply find a variety that grows well under the prevailing conditions.

Another Grassland scientist, Dr. Wayne Polley, who said he doesn’t completely buy the hypothesis of global warming, suggested that a rise in minimum temperatures could lead to a new mix of insects as those that like warm weather extend their range.

Williams said he’d be reluctant to speculate on whether the changes are related to global warming.

Dr. John W. Nielsen-Gammon, who is the official state climatologist, said that, “in general changes in temperature as you describe are too large to be attributed to global-scale processes like global warming.”

Instead, he said, one possible cause might be irrigation.

“Increases in irrigation over the past century would lead to cooler days because with more water available to be evaporated, less of the solar energy goes into heating the ground,” he said. “At night, the increased moisture and higher dew points would lead to higher nighttime temperatures.

“If this is the correct explanation, it is unlikely the trends would continue, because irrigation is on the decline in Texas. Also, the effect would be smaller at locations farther from irrigated farmland.”

On the other hand, Dr. Mark Tjoelker of Texas A&M University, said, “An increase in daily minimum temperatures at night is entirely consistent with warming trends from increased concentrations of greenhouse gasses (such as carbon dioxide).”

Tjoelker is an associate professor in forest ecology, physiological ecology and global change.

Warming daily temperature minimums “is consistent with the evidence of human-caused warming,” he said.

Tjoelker said that if the trends continue, they could change the area’s ecosystem.

“Warmer temperatures may directly negatively impact crop and native plant growth by increasing nighttime losses of carbon,” he said. “However, warmer temperatures in springtime may promote earlier growth. Climate extremes in drought or high temperatures may impact both natural and managed ecosystems and services they provide for us.”

However, Tjoelker warned that a number of challenges face scientists as they try to learn more about climate change, its causes and its effects.

Several research projects are under way in Texas to directly manipulate temperature, water and other global change factors, he said, so experts can better understand what’s happening to the overall environment.

Williams’ research include plotting temperature variations by year and by decade. He found that the daily average has risen only slightly over the 95-year period.

His records show that the highest sustained daily temperatures in Temple were during the drought of the early to mid-1950s.

Sustained cooler highs were recorded in the early to mid-1980s.

Telegram photographer Scott Gaulin contributed to this report.

–Reprinted with permission of the Temple Daily Telegram