State’s top climatologist talks climate change in the Big Bend

FAR WEST TEXAS — Dr. John Nielsen-Gammon assured the audience that they might leave more confused than when they arrived at this weekend’s Climate Change Symposium, which focused on forecasting what might be ahead for climate change in Far West Texas.

Nielsen-Gammon is a professor of meteorology at Texas A&M University and the Texas state climatologist, a position he has held since his appointment by then-governor George Bush in 2000. He was instrumental in the state’s response to Hurricane Harvey, and he has crunched the numbers on Texas, looking at projections for temperatures, precipitation and climate patterns. This weekend, he was forecasting what might be ahead for West Texas.

Raymond Skiles introduced the event, saying a changing climate will impact landowners, conservationists, parks, preserves, people with a few acres, water conservationists, woodland fire responders and others in the Big Bend area. The symposium on climate was co-sponsored by the Big Bend Sierra Club, Presidio County Underground Water Conservation District, Native Plant Society and the Big Bend Conservation Alliance.

“This is a time for us to dispel the rumors and get to the science,” said Dallas Baxter, the president of the local Native Plant Society chapter. But predicting the climate is sometimes like, well, trying to predict the weather. To an audience of over 140 attendees packed into the Espino Conference Center at Sul Ross State University last weekend, Nielsen-Gammon explained the state’s best estimates of what’s to come in the Big Bend region.


The scientist informed attendees that the amount of precipitation in the area is “pretty much flat in terms of no long term change in rainfall. That’s not the case for most of the rest of the state of Texas.”

When the rain falls is just as important as how much has fallen, he said. “Rainfall matters differently over seasons, and even if annual rainfall stays the same, if it rains more in the winter and less in the summer, that’s gonna have a big impact.” So far, Trans-Pecos patterns are holding, and that’s good news.

But while the average seasonal rainfall is generally stable, “Recently we’ve had some seriously dry years and seriously wet years,” he said, calling the recent variations “ridiculously large.”

If rainfall patterns shift into different seasons, water might evaporate or infiltrate into the ground more or less quickly. If rainstorms shift into flash floods, more water runs off the surface, no longer filtering into the ground as effectively as before.

“The projection going forward is for drying in that southwest monsoon region specifically,” he said, pointing to a map that showed a 5% change in the Trans-Pecos, and a much more dramatic dryness just south of that in northwestern Mexico. The region isn’t seeing big changes in the timing of precipitation, “at least not yet,” he added.

Rainfall is projected to become more intense overall, which contributes to lower soil moisture. In the summertime, rainfall can be so intense that there’s not time for it to soak into the soil.

The scientist noted that if you’re relying on surface water for cattle, that’s good.

In general, Texas rainfall has been gaining in intensity.


One consistency decade over decade: rising temperatures. Nielsen-Gammon called the temperature projections fairly straightforward. The 1970s was the coldest decade in Texas in recent history, “but since then, temperatures have been climbing relatively steadily.” There has been a .6 or .7 degree Fahrenheit increase per decade since the 1970s, to which the presenter added, “This is pretty much independent of who’s president for any given time.” It’s getting warmer just about everywhere, he said.

Rising temperatures in the Trans-Pecos means water evaporates before it ever soaks into the ground. If it does go into the topsoil, it gets drawn out of the ground more rapidly by the unforgiving Texas sun.

For plants, high temperatures can dry them out. They open their stomata to take in carbon dioxide from the air, and while open, water from the plant evaporates out.

Carbon Dioxide

Over the past 200 years, the amount of carbon dioxide in the air has increased nearly 50%. Higher temperatures will dry out plants when they open their stomata, but the increase of carbon dioxide in the air can be a perk for plants.

They can collect CO2 a lot faster when it’s plentiful, meaning they can close those stomatas a lot faster, and avoid the drying from the heat. It turns out plants adapted to the Chihuahuan Desert could handle increasing temperatures, reduced water and increasing carbon dioxide quite well.

But if plants can succeed and proliferate, they could end up consuming more water. Climate models simulating all of these inputs show on the whole that despite changes in plants, the combination of factors will lead to decreased moisture in the soil which necessarily means there will be less water infiltrating the ground, replenishing aquifers.

Nielsen-Gammon summarized, “The climate will tend to be more susceptible to drought because once it stops raining, things dry out faster. Plants go dormant faster, they dry out faster, and there’s more fuel.”

Rapid Changes

“We obviously don’t have any observations of future global warming, but we do have the history of past global warming,” he told attendees. Nielsen said a lot can be learned from the last major climate shift, when Earth exited the last ice age 20,000 years ago.

The temperature increase now is about 50x as rapid as it was when Earth came out of the last ice age. The speed of temperature change today will be a lot harder for plants (and the associated insects and ecosystem) to change smoothly with the climate.

“It’s only so rapidly that plants can disperse seeds and pollen. Birds can make the adjustment quickly, insects not so fast.” Plants and trees change slowly. A bird can migrate to a more habitable climate area, but a tree dispersing seeds can only get so far.


“To get fire, you’ve got to have an ignition source, you’ve got to have fuel, you’ve got to have a means for the fire to spread.” Two of the three models that Nielsen-Gammon presented have West Texas in the green, which would mean a reduced fire risk. “The reason they have reduced risk is because they have things drying out so much, there’s reduced vegetation and there’s not enough to burn in the first place,” he explained. One of the three models predicts an increase.

The area could have more droughts and more floods simultaneously, with some years dry and other years wet, but higher temperatures will make the change from wet to dry more rapid, and the more intense rainfall will make the gaps between the rainfall longer. According to Nielsen-Gammon, we might have more fires or we might have fewer fires. Plant growth could expand, or be mercilessly baked in the heat. “I’m still not going to be able to tell you what’s going to happen,” the state’s top climatologist concluded.

Baxter told attendees she was feeling optimistic after the talk. “It’s not as fast as I thought,” she said, though she hoped that wouldn’t stop locals from taking actions to mitigate the negative and impacts of a changing climate.