Planes, trains, and climate change is Mashable's ongoing series about the dramatic impacts transportation has on the planet’s warming, and our lives.

On June 26, as a potent heat wave settled over Europe, atmospheric scientist Patrik Winiger settled into his seat aboard a high-speed electric train traveling from Zurich to Amsterdam. The heat, which would soon topple temperature records across the continent, began to stress the sleek Deutsche Bahn train.

First, the fast-moving German train slowed down. Then, a conductor announced that the train would need to take an extended rest at the next station because the engines were overheating. But before the train even reached the station, it stopped in the middle of the tracks. Inside the halted cars, the AC maxed out and the temperature rose. After a 15-minute breather, the cars again crept forward into the shaded refuge of the Frankfurt airport station. Perhaps the train would cool off, and things would improve.

They didn't.

"Just when [the train] was about to roll out there was a harsh stop," recounted Winiger. "There was another announcement saying, 'there's a train ahead of us on fire.'"

Winiger's experience showcased the "classic problems" of modern railcars succumbing to heat stress, explained Andrew Quinn, a civil engineer at the University of Birmingham who researches the impacts of climate change on infrastructure, particularly railroads. "In extreme conditions you're going to stress all the motors, the AC, and control systems," Quinn said.

"There's a train ahead of us on fire."

These heat-stoked train woes are a growing problem, because scientists globally have repeatedly warned that human civilization will be exposed to more "very hot days" in the coming decades, even if global temperatures are curbed at 2 degrees Celsius (3.6 degrees Fahrenheit) above 19th-century conditions. Limiting warming to this ambitious mark, however, is now nearly impossible, which means trains (and the metal rails they ride on) will almost certainly feel the heat — heat that now regularly breaks or smashes historical records.

"We have a strong inclination based on evidence so far that a likely impact of climate change is more extended and hotter heat waves," said Nick Bassill, an atmospheric scientist at the University of Albany who researches weather and climate risks associated with the transportation industry.

"It was warmer than has ever been experienced on record by humans in France," he added, referencing Europe's scorching June heat wave. "You would imagine that would cause problems for things like rail lines."

The situation is similar across the pond. Earlier in June, triple-digit temperatures caused "major delays" on trains in California's Bay Area, with some trains running almost 40 minutes late. A widespread heat wave across the East Coast in 2018 resulted in slowed Amtrak trains. And during last year's European heat wave, trains in the UK were delayed or canceled.

"This is not a problem that’s going away," emphasized Paul Chinowsky, a civil engineer at the University of Colorado Boulder.

"The impacts are not something that is 10 years away," he added. "It's something that’s happening right now." Winiger, who was delayed two hours in Germany but eventually arrived safely in the Netherlands, agreed.

Critically, the hot weather doesn't just stress modern, high-tech trains. It can weaken and distort the steel rails — a notorious detriment to trains. When it starts getting really hot, the track essentially gets softer, explained Chinowsky. So when a heavy rail car moves over the tracks, it pushes the pliable rail down and out. "It causes the rails to warp," he said.

These warps, also known as buckling or sunkinks, can range from small to extreme, turning rail into wavy, serpentine-like tracks. "It’s kind of scary when you look at it," noted Chinowsky. Running over buckled tracks can easily derail a train, he said. It's easy to see why.

Buckled tracks in the United States. Image: U.S. Department of Transportation

When the risk of buckling rails goes up, trains have to slow down, or sometimes stop completely. "[Railroad companies] stop the rails during the hottest parts of the day," said Chinowsky. "It's happened in Virginia and Arizona."

Slowed trains are the more common result of overheated rails, however. These "slow orders" reduce the energy that a heavy train pushes into the track, thereby avoiding moderate or extreme warping, explained Allan Zarembski, a civil engineer and the director of the Railroad Engineering and Safety Program at the University of Delaware. Too much energy on a heated track will cause the track to buckle.

"So if there is a warming trend, in the short term there will be more slow orders," said Zarembski, noting there are also longer-term engineering solutions available to address the problem.

"This is a fixable problem."

But the resulting delays really add up. Research published this year by Chinowsky in the journal Transport Policy projected that delays stoked by overheated or warped rails would cost the U.S. between $45 to $60 billion by the century's end. These delays mean boosted costs for fuel (or power), crew, and a number of other operational costs.

California's Bay Area Rapid Transit [BART], experienced heat-related delays in June 2019. Image: Shutterstock / Joseph Sohm

Big railroad companies in the U.S., especially those running heavy freight and people across the nation, would be wise to fortify their infrastructure, said Chinowsky. But rail companies haven't been too open about the growing problem. "They’ve done a very good job of keeping this quiet," said Chinowsky. "But as the temperature goes up it becomes harder to hide that you’ve got major delays happening."

Indeed, although some major rail companies in both the U.S. and Europe acknowledged to Mashable the problems caused by extreme heat and responded with online information, no company directly answered a specific question about how they're preparing for a future with more heat waves.

But civil engineers like Quinn and Chinowsky encourage rail companies to address the inevitable problem. After all, no one can argue with the consequences of molecular physics, specifically atmospheric concentrations of heat-trapping carbon dioxide that are increasing at rates that are unprecedented in both the historical and geologic record. As a consequence, 18 of the 19 warmest years on record have occurred since the year 2001.

"Every decision [rail companies] make should take into account climate change," said the University of Birmingham's Quinn. "This is an ongoing thing. The railways are an evolving thing."

Global warming trend since 1880. Image: nasa

"This is a fixable problem," added Chinowsky.

And it will be costly. But climate change is inherently costly.

There are a number of farsighted solutions. A larger scale fix involves installing temperature sensors along tracks to detect portions of rail that have met heat thresholds, which require slowing trains so the tracks don't buckle. "It's an investment," explained Chinowsky, but it can pinpoint the problem and avoid slowing or shutting down a large swath of rail. A sensible but certainly more expensive approach entails replacing track with more heat-resistant steel.

A significantly cheaper alternative calls for painting sections of rail white to reflect the sunlight, which the UK's rail agency, Network Rail, now does.

Engineers also suggest laying down new rail at higher temperatures. The rail, after being bolted to the ground, settles in at warmer conditions and is then able to heat and expand without warping out of place from its moorings. It's kind of like "tuning" the rails to adapt to higher temperatures, explained the University of Albany's Bassill. Though, this comes with a cost, noted Zarembski: Tracks installed at higher temperatures can expand more when heated, but are less able to contract during freezing spells. Under such mounting tensile stress, rail can get ripped apart.

Average temperatures in 1884. Blues show cooler than average. Image: nasa Average temperatures in 2018. Yellows, oranges, and reds show warmer than average. Image: nasa

But, emphasized Quinn, it's not just the rails that have to be made more resilient. "It's the cars. It's the power systems. It's everything," he said, noting international guidance prepared in the report he coauthored, "Rail Adapt: Adapting the railway for the future."

Today, rail companies must stay vigilant during extreme, anomalous heat. And they do. When air temperatures hit 95 degrees in California's Bay Area, for example, heat patrols staffed by track inspectors look "for any sign of [rail] movement with their trained eyes," a Bay Area Rapid Transit (BART) spokesperson said over email. BART uses laser thermometers to measure temperature, and train operators slow to 27 mph if they spot anything unusual on the tracks.

But future delays are inevitable. Temperatures have risen. Earth is already locked in for significant warming this century, regardless of even unprecedented efforts at mitigation. Preparing for extreme heat today, said Quinn, is not the point.

"Think about the standard you need in 30 years' time," he said.