Key Facts

Summers in Dallas-Fort Worth are already long and scorching, and scientists expect global warming to bring even more extreme heat to Texas.⁶ Unless we take steps now to reduce our heat-trapping emissions and develop adaptation strategies, air and ground transportation in this fast-growing region is likely to suffer.^6,7,9

• If our heat-trapping emissions continue to rise at today's rates,⁸ scientists project that average summer temperatures in Dallas-Fort Worth are likely to increase 9-10° F (5.0- 5.6° C) by the end of this century—with 150 to 165 days a year topping 90° F (32° C).⁶
• Scientists expect longer, hotter summers to reduce the carrying capacity of planes and cause flight delays and cancellations at Dallas-Fort Worth and other airports.^6,7
• Airport runways, roads, and train tracks are likely to buckle during longer, more frequent heat waves, raising repair and maintenance costs and putting construction workers at risk of heat stress.^6,11

Details

Dallas-Fort Worth is one of the largest and fastest-growing metropolitan areas in the United States, with an estimated population of more than six million people in 2009.² This North Texas megacity is a major hub for air and ground transportation.

Dallas-Fort Worth International Airport was the world's third busiest in terms of takeoffs and landings, and the seventh busiest in terms of passenger traffic, in 2008.³ More than 57 million passengers passed through the airport that year.³

The area is also a crossroads for the interstate highway system and rail freight traffic.^4,5 Texas ranked first among U.S. states in miles of rail, freight rail employment, and tons of freight received by rail in 2008, as well as third in tons of rail freight loaded.⁵

The climate of North Texas is humid subtropical, with hot summers. For the decade 1961-1971, for example, temperatures in and around Dallas-Fort Worth topped 90° F (32° C) for an average of 90 to 105 days a year.⁶

Extreme heat disrupts both air and ground transportation. Warmer air—which is less dense—reduces the lift produced by the wings of airplanes and the thrust produced by their engines.^6,7 To build up enough speed to take off in hot weather, some planes need either longer runways or smaller payloads.^6,7 Some summertime flights have been canceled because of excessive heat in recent years.⁶

What the Future Holds

If our heat-trapping emissions continue to rise at current rates,⁸ scientists expect average summer temperatures in the Dallas-Fort Worth area to increase by around 9-10° F (5.0- 5.6° C) by the end of this century.⁶ Unless we act now to curb our emissions,⁸ temperatures in the region are likely to top 90° F (32° C) during nearly half of the year by the end of the century.⁶ Today's one-in-twenty-year heat extreme could also become an annual occurrence.⁶

On the other hand, if we make significant efforts to curb our emissions,⁸ scientists project that Dallas-Fort Worth summers are likely to warm an average 5-6° F (2.7-3.3° C) by the end of the century.⁶

Increases in extreme heat are likely to wreak havoc on air and ground transportation in and around Dallas-Fort Worth.^6,7,9 Long periods of extreme heat in summer can damage roads and warp railroad tracks.⁶ Sustained temperatures above 90° F (32° C) can soften asphalt, leading to rutting from heavy traffic.^6,9 Extremely hot weather may also wear out tires and cause car and truck engines to overheat.^6,7 Trains may need to slow down—or could risk derailment on heat-damaged tracks.^6,10

Scientists expect longer, hotter summers to reduce the carrying capacity of planes and cause flight delays and cancellations at Dallas-Fort Worth and other airports.^6,7 One recent study projected that higher temperatures and more water vapor could reduce the summer cargo capacity of a passenger jet by around 17 percent at the Denver airport, and around 9 percent at the Phoenix airport, within a couple of decades.^6,7 Some airports may need to lengthen runways to offset the reduction in aircraft lift and engine efficiency, unless engineers can design more powerful and efficient planes.^6,7,9

Adaptation measures for the rail industry include traveling at slower speeds, reducing the size of trains and lightening loads to shorten braking distances, monitoring rail temperatures, and improving track maintenance.⁹

However, the need to protect transportation workers from extreme heat is likely to limit summertime construction and repairs throughout the sector.⁶ Concern about heat stress for moderate to heavy outdoor work begins at 80° F (27° C), based on an index that combines temperature, wind, humidity, and direct sunlight.^6,11 In urban areas such as Dallas-Fort Worth, heat island effects can worsen the dangers of heat stress.⁶

Credits

Endnotes

1. Photograph used by permission. Jim Simandl. ↑
2. U.S. Census Bureau. 2010. Population estimates: Metropolitan and micropolitan statistical area estimates. Washington, DC. Online at http://www.census.gov/ popest/ metro/ CBSA-est2009-pop-chg.html. Accessed June 30, 2010. ↑
3. Airports Council International. 2009. Airports report flat traffic growth in 2008. Washington, DC. Online at http://www.aci.aero/ cda/ aci_common/ display/ main/ aci_content07_c.jsp? zn=aci&cp=1-5-54_666_2__. Accessed June 30, 2010. ↑
4. Federal Highway Administration. 2010. Interstate density map. Washington, DC: U.S. Department of Transportation. Online at http://www.fhwa.dot.gov/ interstate/ densitymap.htm#face. Accessed June 30, 2010. ↑
5. Association of American Railroads. 2008. U.S. freight railroad industry snapshot. Washington, DC. Online at http://www.aar.org/ AAR/ KeyIssues/ Railroads-States.aspx. Accessed June 30, 2010. ↑
6. U.S. Global Change Research Program. 2009. Global climate change impacts in the United States. Edited by T.R. Karl, J.M. Melillo, and T.C. Peterson. Cambridge University Press. ↑
7. Transportation Research Board. 2008: Potential impacts of climate change on U.S. transportation. Special report no. 290. Washington, DC: National Research Council. Online at http://onlinepubs.trb.org/ onlinepubs/ sr/ sr290.pdf. Accessed April 5, 2010. ↑
8. The emissions scenarios referred to here are the high-emissions path known as A2 and the low-emissions path known as B1 from the Intergovernmental Panel on Climate Change. ↑
9. Field, C.B., L.D. Mortsch, M. Brklacich, D.L. Forbes, P. Kovacs, J.A. Patz, S.W. Running, and M.J. Scott. 2007. North America. In Climate change 2007: Impacts, adaptation, and vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Edited by M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden, and C.E. Hanson. Cambridge University Press, pp. 617-652. ↑
10. Savonis, M.J., V.R. Burkett, and J.R. Potter. 2008. Impacts of climate change and variability on transportation systems and infrastructure: Gulf Coast study, Phase I. Synthesis and assessment product 4.7. Washington, DC: U.S. Climate Change Science Program. ↑
11. Occupational Safety and Health Administration. 2008. Heat stress. In: OSHA Technical Manual, Section III—Chapter 4. Washington, DC: U.S. Department of Labor. Online at http://www.osha.gov/ dts/ osta/ otm/ otm_iii/ otm_iii_4.html. Accessed June 30, 2010. ↑