WASHINGTON – Debate over the size of the auto industry’s role in global warming continues to exist, but experts say beyond the controversy lies the fact climate change is occurring and could profoundly affect the transportation sector.

At the recent Society of Automotive Engineers Government/Industry annual meeting here, experts offered data linking global warming to growing greenhouse-gas emissions from sources such as automobiles and provided a sobering analysis of its potential impact on the U.S. transportation infrastructure.

In short, auto makers later this century could face a network of roads, bridges, tunnels and ports weakened by more frequent severe weather, suggests civil and environmental engineer Henry Schwartz Jr.

That arguably could limit car and truck sales, because consumers would find driving more dangerous and less enjoyable and manufacturing and distribution would become less efficient and more expensive.

Among leading greenhouse-gas sources, the transportation industry ranks fourth behind energy, deforestation and agriculture, according to the Intergovernmental Panel on Climate Change (IPCC).

“About a month ago in St. Louis, we had a record-breaking flood on the Meramec River,” Schwartz tells the conference. “And Cape Girard, 100 miles (161 km) south, had 12 ins. (30 cm) of rain in 24 hours. That’s more than Los Angeles gets in a year.

“The old Route 66 came within inches of being closed; flood waters were lapping at its edges. That’s a major route to the Midwest and Southwest.”

In fact, as Schwartz spoke, the Mississippi River was cresting at St. Louis, a result of heavy rains and snow melt in the Upper Midwest.

That is “warning us, reminding us, of the great 1993 flood, when bridges from St. Louis north 250 miles (km) were out of service because you could not get to them,” says Schwartz, committee chair for a National Academies study on the effect of climate change on U.S. transportation.

“So are these things climate change? Perhaps not, at least not directly,” he says. “But extreme weather events like these may become more frequent as a result of climate change.”

Climate change is real, says Benjamin D’Angelo, an analyst at the Environmental Protection Agency. He says global emissions from a spectrum of sources rose 70% between 1970 and 2004.

Citing data from the most recent IPCC report, which world scientists consider a consensus reference document on climate change, D’Angelo says emissions of carbon dioxide account for 77% of that total.

CO2 ranks as the most prominent greenhouse gas on Earth and warms the atmosphere more than any other source, ahead of methane and smog. The level of CO2 present between 1970 and 2004 grew 80%.

In 2005, D’Angelo says, global atmospheric concentrations of CO2 and methane “far exceeded” their natural levels over the last 650,000 years, due primarily to fossil fuel use. As a result, humans have been warming the Earth since 1750, and the average temperature over the last century has increased by about 1° F (0.6° C).

“What is causing this trend?” D’Angelo asks. “The IPCC says very likely a growing concentration of greenhouse gases.”

Left unchecked, D’Angelo says global temperatures could rise between 3.2° F (1.8° C) and 7.2°F (4° C) by 2100. And although industries and consumers today are taking steps to curb the warming, such as building vehicles with greater fuel economy or capable of burning biofuels, global temperature will be affected minimally between now and 2033 because of all the greenhouse gases “already in the pipeline.”

Scientists probably won’t see significant impact from the mitigation efforts until the turn of the century, he says.

D’Angelo says IPCC scientists expect moderate climate change in the U.S. and Canada over this century, with particular warming in the western mountains from the decreased snow pack. Fire risk will rise. Although agricultural yields should increase, variability between growing regions, as well as disturbances from pests and crop disease, also will climb.

Urban areas will witness more frequent heat waves, while coastal communities and habitats will endure the stresses of climate change compounded by development and pollution, the analyst says.

In addition, it means an already aging U.S. transportation infrastructure will find itself under greater stress over the next century, says Schwartz, whose report is one of the first to examine the effects of climate change on transportation, rather than transportation’s influence on climate change.

Likely climatic impacts on the transportation system include rising sea levels that may flood tunnels, erode bridges and force the reconfiguration of harbors and ports. The report also concludes storm surges could become more severe, require larger evacuations, lead to major airport closures and incapacitate rail lines.

More hot days and more frequent heat waves would result in thermal expansion of bridges and pavement, deform rail tracks and restrict airline flights, Schwartz says. And while increased arctic temperatures may open the Northwest Passage and shorten shipping routes, it also could thaw permafrost and sink some roadways, rail beds, pipelines and runways.

Heavier, more frequent storms and deadlier hurricanes would mean more traffic disruption. The change in weather also would upset historical patterns developers use for planning.

“The climate is changing in ways we’ve never seen before,” Schwartz says. “How will we design the size of our culverts and the height of our bridges? It’s time to begin to address climate change as a routine part of our planning. Reacting to events simply is not satisfactory any longer.”

Recommendations from Schwartz’s committee include public and private entities taking inventory of critical infrastructure in vulnerable areas; incorporating climate change and emergency response into capital-improvement programs and developing plans for new and rehabilitated transportation infrastructure with better risk analysis from more sophisticated methods.

It also calls for improved communication between engineers and climate scientists and rebuilding infrastructure in critical locations, while developing new technologies to track their condition and warn of pending failure.

Infrastructure must be rebuilt to a new standard, not rehabilitated to its original condition as most federal and state rules demand.

Communication between the transportation sector and federal, state and local authorities with conflicting land-use interests needs to improve, Schwartz says.

“Transportation professionals tend to steer clear of that morass, but we’ve got to draw land-use planners into our circle of discretion,” he says.

Schwartz admits skepticism over global warming exists in the transportation sector. He says most professionals consider global warming a natural occurrence the sector will overcome no differently than the floods, fires, ice storms and mudslides already successfully endured.

“But the time has come to begin to understand the threats of climate change and give important consideration to developing and maintaining the transportation networks in our country,” he says. “We can wait 50 or 100 years to make absolutely certain climate change is real before we act, but if today’s scientists and science are right it could be too late in 50 or 100 years.”