A tale of two climbers: hypothermia, death, and survival on Mount Everest.

Hypothermia is an acknowledged risk for those who venture into high altitude regions. There is however little quantitative information on this risk that can be used to implement mitigation strategies. Here we provide an analysis of the meteorological and hypothermic risk parameters, wind chill temperature, and facial frostbite time, during the spring 2006 Mount Everest climbing season. This season was marked by two high profile events where a solo climber was forced to spend the night in highly exposed conditions near the summit. One climber survived, while the other did not. Although this retrospective examination of two individual cases has admittedly a small sample size, and there are other factors that undoubtedly contributed to the difference in outcomes, we show that wind chill temperature and facial frostbite time experienced by the two climbers were dramatically different. In particular, the climber who did not survive experienced conditions that were approximately one standard deviation more severe that usual for that time of the year; while the climber who survived experienced conditions that were approximately one standard deviation less severe then usual. This suggests that the environmental conditions associated with hypothermia played an important role in the outcomes. This report confirms the importance of providing quantitative guidance to climbers as the risk of hypothermia on high mountains.