"There was something called global warming," Yona says, lips pursing thoughtfully. That's something she knows very little about as well, but she's heard the words often enough, one thing that didn't go forgotten or unmentioned in growing up on the train. "People used a chemical to try to stop it, but it did too much. Made everything too cold instead." She can still see it sometimes, the world of white outside dirty windows, such a far cry from the warm greens of Darrow's spring. She misses it and she doesn't all at once. "So it froze."