It starts with mumbling and stumbling. Then come violent shivers and then, paradoxically, a false sense of warmth that makes some people strip their clothes off. Eventually, they may curl into a fetal position as their muscles go rigid, their skin goes waxy, and the heart slows down, then stops. Whether two climbers missing on Mount Hood for more than a week are still alive is not clear. But if they are somehow still hanging on in the brutal cold and howling winds, perhaps hunkered down in a snow cave, they may be going through what veteran climbers say is...