More than 90 deaths this season: Are we seeing more avalanches?

Recent deadly incidents in California and Europe are putting avalanches - and how to avoid them - in the spotlight. More than 90 deaths this season: Are we seeing more avalanches?29 minutes agoShareSaveRobert GreenallBBC NewsShareSaveAvalanches in Switzerland and Italy caught on cameraIt is not unusual for avalanches to be in the news in the northern hemisphere at this time of year, the height of the annual ski season.But Tuesday's deadly incident in California, which took the lives of eight skiers and left one more unaccounted for, and the difficult situation in much of the Alps - where there have been more fatalities than usual this year - has put a spotlight on avalanches and how prepared winter sports enthusiasts should be for them.The two situations would seem to be very different. California has been coming out of a so-called snow drought and experts do not consider the latest snowfall exceptional. But droughts followed by intense snow can cause problems - the new snow is unable to bind to old snow underneath, which can either be very hard or non-existent, and therefore remains loose.ReutersRescuers are searching for one skier still unaccounted for in blizzard conditions in Nevada County, CaliforniaEurope, however, has seen two major storms in a week and a large amount of heavy snow combined with strong winds, leading to high avalanche warning levels across an unusually large part of the Alps. Three Britons were among dozens killed in incidents so far over the season.One Alpine resort suggested that the current conditions could be the worst there this century.Recent snows have also led to evacuations of several communities in Switzerland and northern Italy, as well as power outages and a train derailment at Goppenstein in the south-western Swiss canton of Valais.But is there a connection between events in Europe and California? Is climate change to blame?Climate change might seem an obvious culprit for the unstable weather conditions that have brought them about."There is evidence that climate change will lead to sharper, more intense precipitation followed by long periods without," Simon Mason, senior scientist at SEI US, told the BBC. This would seem to be the case in Europe, which has recently had several seasons with lower than average snowfall, and some dry periods in the early part of this season."However, since many factors control avalanche risk and precipitation is only one controlling influence, it is difficult to conclude how risks may evolve with future climate change," Mason said.Climatologist Christoph Marthy told Swiss outlet SRF the current Alpine winter - with weather until recently dominated by high pressure and several long, dry periods - is exactly the opposite of a typical climate change winter.Benjamin Zweifel, of the Swiss Federal Institute for Snow and Avalanche Research, told the BBC the storms were "only one piece of the puzzle"."The main challenge this winter was a very weak snowpack [an accumulation of snow that compresses and melts seasonally] with very persistent weak layers, caused by long periods without new snow and low temperatures," he said.Antoine MartignonThe Val d'Isere resort described the situation as of Thursday as perhaps the worst this centuryWhile global warming affects weather patterns, the temperature itself could also have a direct impact on avalanches. According to the US Northern Rocky Mountain Science Center, wet snow avalanches - which are likely to become more frequent as temperatures rise - are dangerous, difficult to predict and relatively poorly understood compared with the dry snow equivalent."Wet snow avalanches are caused by weakening in the strength of the snowpack, often triggered by rain, abundant sunshine, or warm temperatures," the centre says in an article on wet snow avalanche research, adding their frequency was expected to increase with changing temperatures. A 2021 research paper in the journal Frontiers in Physiology suggests wetter and warmer snow may also adversely affect a person's chances of surviving an avalanche, while thinner snow cover may increase the risk of blunt trauma injuries.Broadly, there would seem to be four destabilising issues that are changing the dynamics of avalanches - switching between droughts and heavy precipitation, the precipitation itself, wetter snow and snow which is actually melting.How are resorts mitigating the risk?Blaise Agresti, a high-mountain guide at Chamonix, told France's Sud radio that there was another important factor in Europe's spike in avalanche deaths - the changing behaviour of skiers and higher levels of risk."People are increasingly practising off-piste skiing. Among skiers, 25% go off-piste," he said.Way-marked pistes are generally protected by pre-emptive avalanche blasting, and their snow is flattened and compacted to further reduce the risk. If there is still a danger of avalanches, pistes can be closed off, as has happened during the recent warnings.But while forecasting and blasting techniques have improved in recent years, it is not impossible for avalanches to hi