Climate change to bring North Texas longer droughts, heavy rains, 120-degree temps within 25 years

Tom Fox

The United States has just come off a record year for weather and climate disasters and, by most accounts, it’s only going to get worse.

Last year hurricanes Harvey, Irma and Maria; the wildfires and floods in California; and tornado outbreaks in the Midwest and the South delivered $306.2 billion in damages, more than any year in history when adjusted for inflation.

Texas is particularly vulnerable to a changing climate. It has had more costly weather-related disasters than any other state, and those events will happen more often as air and ocean temperatures climb, scientists say.

Category 4 hurricane made landfall near Rockport, Texas causing widespread damage.

Severe hail and high wind damage impacting numerous states including MN, WI, WY, TX, IA, IL, KS, MO, NE, NY, PA, VA.

Hail storm and wind damage impacting several states including CO, OK, TX, NM, MO.

A period of heavy rainfall up to 15 inches over a multi-state region in the Midwest caused historic levels of flooding along many rivers.

Large hail and high winds in Texas north of the Dallas metro region caused widespread damage to structures and vehicles.

High wind damage occurred across southern California near San Diego followed by 79 confirmed tornadoes during an outbreak across many southern states including AL, FL, GA, LA, MS, SC and TX.

Sustained period of severe thunderstorms and tornadoes affecting several states including Montana, Colorado, Kansas, Missouri and Texas.

Tornadoes and severe storms cause widespread damage across the Plains and Central states (NE, MO, TX, OK, KS, CO, IL, KY, TN) over a multi-day period.

Large outbreak of tornadoes affects numerous states across the South and Southeast.

A period of extreme rainfall up to 17 inches created widespread urban flooding in Houston and surrounding suburbs.

Widespread severe hail damage across north and central Texas including the cities of Plano, Wylie, Frisco, Allen and San Antonio.

Large hail and strong winds caused considerable damage in heavily populated areas of north Texas.

Multiple days of heavy rainfall averaging 15 to 20 inches led to widespread flooding along the Sabine River basin on the Texas and Louisiana border.

Early outbreak of tornadoes and severe weather across many southern and eastern states including (AL, CT, FL, GA, LA, MA, MD, MS, NC, NJ, NY, PA, SC, TX, VA).

A powerful storm system packing unseasonably strong tornadoes caused widespread destruction in the Dallas metropolitan region, damaging well over 1,000 homes and businesses.

A slow-moving system caused tremendous rainfall and subsequent flooding to occur in Texas and Oklahoma.

Tornado outbreak across the Southern Plain states (IA, KS, NE, OK, CO, SD, TX) with 122 tornadoes.

Severe storms across the South and Southeastern states (AL, AR, FL, GA, KS, LA, MS, NC, OK, SC, TN, TX).

Severe storms across the Midwest and Ohio Valley including the states (AR, IA, IL, IN, KS, KY, MI, MO, NC, OH, OK, PA, TN, TX, WI, WV).

Historic drought conditions affected the majority of California for all of 2014 making it the worst drought on record for the state.

Severe storms across the Plains states (IL, KS, MO, TX) causing considerable hail and wind damage in Texas.

The 2013 drought slowly dissipated from the historic levels of the 2012 drought, as conditions improved across many Midwestern and Plains states.

Continued drought conditions and periods of extreme heat provided conditions favorable for a series of historic wildfires across Texas, New Mexico and Arizona.

Drought and heat wave conditions created major impacts across Texas, Oklahoma, New Mexico, Arizona, southern Kansas, and western Louisiana.

Dozens of tornadoes and severe storms affect the states AR, IL, IN, KY, MO, OH, TN, TX across the Ohio Valley and South.

An outbreak of tornadoes, hail, and severe thunderstorms occurred across Oklahoma, Kansas, and Texas in mid-May.

Residual and sustained drought conditions across western and south-central states resulted in thousands of wildfires.

Complex of severe thunderstorms and high winds across the region (TN, KY, OK, OH, VA, WV, PA).

Outbreak of tornadoes over portions of the midwest and south during a week-long period-affecting the states of AL, AR, KY, MS, TN, TX, IN, KS, MO, and OK.

The persistent remnants of Tropical Storm Allison produce rainfall amounts of 30-40 inches in portions of coastal Texas and Louisiana, causing severe flooding especially in the Houston area, then moves slowly northeastward; fatalities and significant damage reported in TX, LA, MS, FL, VA, and PA.

Outbreak of F4-F5 tornadoes hit the states of Oklahoma and Kansas, along with Texas and Tennessee, Oklahoma City area hardest hit.

Very heavy snowstorm (1-4 feet) over Appalachians, Mid-Atlantic, and Northeast; followed by severe flooding in parts of same area due to rain and snowmelt.

Torrential rains, hail, and tornadoes across Texas-Oklahoma and southeast Louisiana-southern Mississippi, with Dallas and New Orleans areas (10-25 inch rains in 5 days) hardest hit.

Tornadoes and severe storms cause damage in states across the South, Southeast and Midwest.

Intense ice storm with extensive damage in portions of TX, OK, AR, LA, MS, AL, TN, GA, SC, NC, and VA.

Torrential rains cause flooding along the Trinity, Red, and Arkansas Rivers in TX, OK, LA, and AR.

"Climate change is not just about polar bears," said Katharine Hayhoe, a climate scientist at Texas Tech University with an impressive YouTube following. "It will affect North Texas profoundly."

Between 2041 and 2050, Dallas-Fort Worth may see August temperatures rise from a mean of 86 degrees Fahrenheit at the end of the 20th century to 94 degrees, with extremes rising above 120, reports one study by scientists at the University of Texas at Arlington.

Longer droughts and more extreme rainstorms will pose a challenge for those who manage drinking water supplies, those who raise cattle, and those who oversee our roads and railways.

The changes may also have unexpected effects on people’s daily lives, including jobs. Intense heat can imperil cars and airplanes, evaporate drinking water supplies, and halt outdoor labor such as farm work and construction.

Adam Smith, a scientist with the federal government’s main climate agency, the National Oceanic and Atmospheric Administration, calls Texas "the disaster capital of the United States."

As Smith explains, Texas is susceptible to almost every kind of weather and climate hazard, from extreme cold to extreme heat, from severe drought and wildfires to torrential floods. Texas is also home to a booming population and critical infrastructure, including the petrochemical plants that were damaged in Hurricane Harvey.

"Texas is a hot-spot for a wide range of extreme natural events due to its geography," said Smith. "We expect many of these extremes to become more frequent and intense as time moves forward."

While uncertainty is built into climate models, scientists have a high degree of confidence in many of the changes they observe and predict.

The bigger, longer and more common an event is, the greater the accuracy with which scientists can project how climate change will impact it, said Hayhoe, a lead author of a November 2017 climate change report overseen by scientists at 13 federal agencies. Larger events have more data associated with them and can be easier to model.

Climate scientist Katharine Hayhoe

Researchers are very confident that climate change will increase both average and extreme temperatures. They are also confident that climate change is likely to increase the risk of heavy precipitation in many areas and may bring stronger droughts to the south-central and southwestern parts of the U.S.

Projected impacts on smaller-scale events like tornadoes and hailstorms are less well understood.

One area of consensus is the cause of climate change. "It is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century," note the authors of the Fourth National Climate Assessment, a Congressionally mandated review that scientists conduct every four years. They add that there are no convincing alternative explanations.

Here is how these changes will affect our area, the evidence behind the projections, and how confident scientists are in each of these findings.

More record-setting heat in North Texas is a virtual certainty. Already, we are living through the warmest period in the history of modern civilization, the federal report found, and that warming will accelerate.

Climate science contrarians often attack the models on which climate projections are based. Myron Ebell, who led President Donald Trump’s transition team at the Environmental Protection Agency, accepts that humans are most likely responsible for warming, but he says models have exaggerated the outcome. Ebell is director of the Center for Energy and Environment at the Competitive Enterprise Institute, a libertarian advocacy group based in Washington, D.C. He acknowledges that he is not a scientist.

In fact, researchers have used models to predict global temperature changes for more than 50 years, and the models’ projections have been fairly accurate over the long term. In the early 21st century, a discrepancy appeared between observed and modeled temperatures — a period dubbed the "global warming slowdown" or "hiatus."

Scientists have published scores of studies on the mismatch and tied it to several factors that contributed to lower-than-expected observed temperatures. Those factors include a series of small volcanic eruptions, the cooling effects of which scientists had underestimated, and lower than expected solar output.

Findings from those studies are helping to improve climate model simulations and helping scientists better understand why there are differences between simulations and observations in the early 21st century, said Ben Santer, a climate scientist at the Lawrence Livermore National Laboratory.

Global average temperatures increased about 1.8 degrees Fahrenheit in the last 115 years. In Dallas, they climbed from about 65 degrees Fahrenheit during the early part of the 20th century to 68 degrees Fahrenheit during the most recent decade. If nothing is done to reduce emissions of carbon dioxide and other greenhouse gases, average temperatures in the city may reach the low 70s by 2050 and surpass 75 degrees by the end of the century.

The Dallas area warmed twice as fast as the North Texas region as a whole due to urbanization combined with long-term warming, said John Nielsen-Gammon, Texas’ state climatologist and a professor at Texas A&M University.

Rapid development in Dallas accelerates the so-called "urban heat island" effect. Man-made building materials absorb and lock in more heat than soil and natural landscapes, so urban areas are generally warmer than rural areas, especially after sunset.

While some northern areas stand to benefit from warmer weather, that is not the case for Dallas-Fort Worth. "North Texas and a lot of the southern United States are quite close to thresholds where things get really bad," said Amir Jina of the University of Chicago’s Harris School of Public Policy.

Earlier this year, he and colleagues published a study in the journal Science that estimated economic damage from climate change in each county of the U.S.

Once temperatures reach the high 90s, equal to or above body temperature, fatality rates go up.

And Jina’s study predicts 24 extra deaths per 100,000 people each year in Dallas County by the end of the century if global emissions increase at the same rate they have been. That would be 600 extra deaths per year at the county’s 2015 population level.

Heat also affects roads. A 2015 study by the University of Texas at Arlington that focused on the impact of climate change on transportation predicted "an increase in wildfires along paved highways, heat-induced stress on bridges and railroads, air-conditioning problems in public transport vehicles and heat-related accidents by failure of individual vehicles and heat-related stress."

Some of these changes are already happening. In January, grass fires in Parker and Denton counties forced evacuations and road closures.

The study concluded, "These impacts can be translated into substantial mobility and economic loss."


Along with heat will come stronger drought, which "has profound economic impacts," said Hayhoe.

The prediction that North Texas will have longer and more severe droughts is based on multiple factors, including the relationship between high temperatures and soil dryness and the presence of more frequent and longer lasting high-pressure systems in summer that suppress rainfall and deflect storms away from our area.

Hayhoe points to Texas’ 2010-2013 drought as a probable sign of things to come. Although this drought occurred naturally, as a result of a strong La Niña event that typically brings dry conditions to our area, it was exacerbated by extreme heat. That event created severe hay shortages for cattle farmers and led some ranchers to prematurely slaughter their herds or export them out of state.

"Cotton can be drought-resistant, but not cattle," said Hayhoe.

The 2015 UTA study predicts a reduction in soil moisture of 10 percent to 15 percent in all seasons by 2050, which can also lead to cracked pavement and the premature loss of roads, railways and other infrastructure.

Heat and drought also pose a problem for drinking water supplies, which North Texas sources from surface reservoirs that will be increasingly prone to evaporation. Hayhoe says some water managers are considering pumping the reservoirs underground during exceptionally hot and dry conditions, or covering them with polymer "blankets."

The blankets are an invisible layer of organic molecules that can help reduce evaporation.

While it’s not likely that annual precipitation totals will change in North Texas, rainfall patterns likely will. Hayhoe and Nielsen-Gammon both say we will likely see enhanced "feast or famine" cycles with torrential rainstorms in the spring followed by longer than usual dry periods.

These predictions carry a high degree of certainty, because climatologists have already recorded this trend playing out.

"Rainfall becoming more extreme is something we expect because we’ve observed this not just in North Texas but throughout the U.S., and models consistently predict it will continue to happen," said Nielsen-Gammon.

Warm air holds more water vapor, which feeds rainstorms. If annual rainfall totals do not increase, that translates to longer dry spells in between the downpours.

Severe rainstorms, the UTA scientists predict, will have the capacity to flood highway exit and service roads in the FEMA 100-year flood plain.

"While the state highway system was built above flooding levels, the connector roads may be easily flooded," said Arne Winguth, a climate scientist at UTA who co-authored the report.

Two events climate scientists cannot reliably project are hailstorms and tornadoes. "A lot of the things we care about are too small-scale to predict with more confidence," said Nielsen-Gammon. "The historical record is not large enough for longer-term forecasts."

Arne Winguth, a climate scientist at UT Arlington studies the effects of climate change on North Texas’s infrastructure. (Nathan Hunsinger/The Dallas Morning News)

The same is true with hail. "One thing we expect to happen with a warming climate is that the average humidity in the lower atmosphere may decrease, and if that happens it’s easier for hail to stay frozen," said Nielsen-Gammon. "That factor might increase hailstorms, but that’s just one of many factors that do affect hail."

Jina of the University of Chicago predicted in his study that climate change would decrease Dallas County’s annual income by 10 percent to 20 percent in the coming decades unless emissions are reduced. "North Texas is one of the worst-affected places in the country," he said. Much of the loss comes from higher mortality rates, soaring air-conditioning costs and reduced labor productivity.

To track labor productivity, Jina and his colleagues examined national time-use surveys — diaries kept by thousands of volunteers across the country — and compared them with local weather data. He found that on extremely hot days, people tended to stop working about 30 minutes early.

"There’s direct evidence that people concentrate less well, make more mistakes and their brain just functions less efficiently if it’s too hot," he said. Heat also disrupts sleep. "The general lack of productivity leads to them saying, ‘No more work today.’"

The good news is that many climate-change effects are manageable. They do require local and federal authorities to plan ahead and take action, said Smith of the National Oceanic and Atmospheric Administration.

"It is important," he said, "to address where we build, how we build and also to build protections for populations already exposed in vulnerable areas."

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