Perhaps that outlook can explain the warning offered by the China Meteorological Administration at a meeting in the Tibetan capital of Lhasa in early May that Tibet was warming faster than anywhere else in China. According to an account published by the Xinhua News Agency, China's state media service, the administration's chief, Zheng Guoguang, said that the railway may be in jeopardy and that the region must "tackle" the effects of climate change. Zheng warned that, where the railway crosses plateau regions, the thickness of the permafrost had been decreasing by as much as 25 centimeters each decade.
Other research points to the railway itself as a contributing factor. A 2007 paper published by the University of Colorado at Boulder's Institute of Arctic and Alpine Research indicated that the more delicate, warm permafrost areas are more affected by the climate warming because their natural balance has been upset by the construction's disturbance of the land. Whereas it would take about 20 years for the warm permafrost regions to thaw under present climate change conditions, the paper says it could take just five years for that permafrost underneath the disturbed land to reach the melting point. The study, published in Arctic, Antarctic, and Alpine Research, was written in part by Chinese scientists close to the railway project.
That research, however, is general to the region and does not examine the railway itself. Nor does it account for effectiveness of the methods that engineers used to cool the soil while they built the tracks. Methods included using pipes called thermosiphons along the sides of the tracks to refrigerate vulnerable parts of the soil along the highest parts of the plateau, an area that comprises the largest continuous sub-Arctic permafrost region on the planet. These cooling sticks are 7.6-meter-long steel tubes drilled into the soil; they contain ammonia, which draws latent heat out of the soil as it evaporates. The technique has been used along the Trans-Alaska Pipeline and in Siberia, although those projects relied on the cooling sticks to a far lesser extent than the Tibet project and were built in colder climes.
The railway, which connects Lhasa to the China's national railway network, the largest in the world, traverses the Tibetan Plateau 5,182 meters above sea level and crosses about 550 kilometers of some of the most delicate and treacherous frozen soil regions on Earth. Half of the permafrost beneath the rails is within –1 degree C, meaning that it could melt with just a degree of climate change.
Some question whether the engineers who planned the railway made the proper calculations to account for long-term climate change. The project's chief engineers counted on cooling sticks and other tricks to help the rails withstand soil warming of 0.2 degree C and air warming of 2 degrees C on the plateau over the next 50 years. The figures—decided on in early 2003—were the least conservative, and thus the least expensive, to accommodate.