by Avalanche forecasters say they are seeing the likely impacts of climate change on Scottish mountains.
The Scottish Avalanche Information Service said conditions are changing faster and avalanches are happening in shorter timescales.
He said named storms — such as 2021’s Storm Barra — brought brief, significant periods of “true winter,” increasing avalanche risk.
The storms were often followed by rising temperatures and snow loss.
But SAIS warned that even in those ‘thinner’ times when there was less snow the potential dangers remained, often higher towards the top of gullies and mountain peaks.
Coordinator Mark Diggins said: “It’s always been harsh weather in Scotland in winter and things can happen quite quickly.
“This is something we’re continually trying to convey to people who go out into the hills who may not appreciate that they’re basically entering a subarctic landscape.”
But he added: “I would say what we’re experiencing now is really rapid changes from one extreme to the other, both in terms of temperature and wind speed, and in the amount of snow.
“For us who broadcast forecasts, which are offered over a 24-hour period, the risk could be considerable when we broadcast it and then the next day everything has been transformed and it’s a smaller risk.”
The rapid changes in conditions in the Scottish mountains have been evident over the last few weeks.
The snowy days were followed by warmer temperatures and significant snow loss over the weekend.
The potential avalanche danger in the six mountain areas monitored by SAIS went from “considerable” to “low” almost overnight.
Meteorologists in Torridon reported burns and rivers at levels usually seen after heavy rains, but this time swollen by snowmelt.
SAIS Lochaber said temperatures rose rapidly in the early hours of Saturday, while the Northern Cairngorms service team ironically described conditions as “tropical” on Monday.
Since then the various teams have again reported dropping temperatures.
Diggins said data from the Met Office showed January/February temperatures atop Cairn Gorm, one of Scotland’s most famous mountains, have averaged two degrees higher over the past 30 years than in the previous 30.
He said another likely sign of climate change was that the snow line, the boundary between snow-covered and snow-free terrain, seemed to creep higher up the mountains.
SAIS forecasting teams use internationally recognized criteria to assess the avalanche risk on mountain slopes.
Most of the work is done in the hills, and some of the work involves digging boreholes in large areas of snowpack, known as the snowpack, to find weak spots in the snow layers that could trigger an avalanche.
Mr Diggins said it had previously been possible for meteorologists to identify ‘signals’ – signs of potential hazards – soon after deciding to carry out an avalanche assessment.
But he said: “What we’re seeing in general is the snowline, which used to be quite low, is now much higher, so we don’t see those signs that we generally have to start thinking about any avalanche danger.”
Almost 90 avalanches have been recorded so far this season and 162 last winter.
In the last 13 winters, the maximum number of avalanches recorded by SAIS was 350 in 2013-14 while the minimum was 90 in 2016-17.
SAIS provides daily avalanche danger forecasts from mid-December to mid-April for six areas: Lochaber, Glen Coe, Northern Cairngorms, Southern Cairngorms, Creag Meagaidh and Torridon.
Areas include Britain’s highest mountains including Ben Nevis, Ben Macdui and Braeriach, and popular peaks such as Cairn Gorm, Liathach and Buachaille Etive Mòr.
The service was started by Hamish MacInnes, a legendary Scottish mountaineer nicknamed the Fox of Glencoe. It has been running in its current format since the 1980s.
SAIS provides daily avalanche danger forecasts on its website and an app.
It uses colors to indicate the level of avalanche probability, with green for low and rising to black when the risk is deemed very high.
There’s also a “rose,” a graph showing the distribution and altitude of potential avalanche hazards, and a set of symbols to help explain the cause of the problem.
Mr Diggins said it was important for people to delve into the details of reports to understand the potential danger of avalanches before embarking on trips to the mountains.
Dr Mike Spencer, who works on financial and climate challenges with the University of Edinburgh’s Smart Data Foundry, said research suggests Scottish winters are changing.
He said the Snow Survey of Great Britain, a dataset collected from the 1940s to the mid-2000s, had recorded that the number of days with lying snow had decreased since the 1990s.
Dr Spencer said: ‘Since the snow survey ended there have been a handful of very snowy winters, 2009/10 and 2017/18, but many winters the snow cover has been less consistent than in the past.’
He said the future was expected to see warmer average temperatures and more changing weather conditions due to climate change.
Dr Spencer added: ‘This changeable weather is likely to mean periods of heavy rainfall alternating with drought conditions, something we are already seeing with increased frequency.
“In the mountains, rising temperatures are likely to mean fewer days of precipitation falling as snow, and when it does, the duration it lies for will be reduced.”
He said climate models suggest Scotland could still see winters with very heavy snowfall, but over time this should become a less frequent occurrence as average temperatures warm.
