Scientifc American: Building a railway across the unstable soil of the Tibetan Plateau was an improbable endeavor from the start, but an army of Chinese government engineers did it anyway. Now, with the frozen soil disturbed by the process of laying down the rail and a warming climate on the plateau, some scientists question whether the $4-billion rail line will survive as is or require major reconstruction. Three years after the railway opened in 2006, international research shows that the …