High Hopes and Broken Dreams – The interplay of climate change, natural hazards, and the mortality of high mountain expeditions in the Nepal Himalayas

High mountain expeditions in the Nepal Himalayas occur in a region particularly prone to natural hazards, fueled by the accelerating impacts of ongoing climate change. These hazards, such as avalanches, rockfalls and serac falls, are amplified by rising temperatures and glacier melt. Despite growing awareness, a systematic exploration of the interplay between climate change, natural hazards, and the high-altitude mountaineering, which plays a dominant economic role for Nepal remains absent.

Our study addresses this gap by analyzing how climate change, natural hazards, and expedition success and/or mortality rates relate. Leveraging a comprehensive dataset (The Himalayan Database, spanning 1905–2019), state-of-the-art meteorological reanalysis data (ERA5-Land), we developed Bayesian hierarchical multilevel models to quantify temporal trends in success and/or mortality and how they relate to trends in natural hazard occurrence. We selected 29 peaks above 7,000 m with over 20 expedition entries resulting in an expedition catalogue containing 7,747 expedition entries. We focused on impacts of extreme conditions, storms, avalanches, and seracs. A text-mining approach classified climbing routes and identified hazard occurrences based on expedition logs.

Our first findings reveal notable trends. First, summit bid time windows, i.e. the time between leaving the basecamp and reaching the summit, has consistently decreased over time, potentially reflecting a shortening of optimal and stable climbing conditions which we demonstrate to deteriorate as a function of climate change. Alternatively, shortened summit bid time windows may be indicative of increasing efficiency of touristic mountain expeditions. Second, the reported incidence of storms and avalanches has declined relative to the total number of expeditions, while the mortality rate associated with these hazards, however, has increased, with avalanche-related fatalities rising from 0.150 to 0.195. Likewise, storm-related mortality also slightly increased from 0.010 to 0.014. This finding suggests that expeditions are likely better prepared for summit bids, e.g. improved weather forecasts, yet that the magnitude of deadly incidents may have increased over time. Third, our analysis of climate and weather data reveals that mountaineering expeditions in the Himalayan region are increasingly subject to extreme weather events and hazardous compound events such as snowstorms.

Our findings underscore the need for enhanced safety measures and a deeper understanding of climate-hazard dynamics to mitigate risks to mountaineers. This study may help advancing our knowledge of how global warming alters the risk portfolio high mountain explorers are exposed to, eventually providing valuable insights for stakeholders in mountaineering and tourism.