The answer to this is unquestionably yes. I’ve been walking in the Scottish mountains regularly since 1993 and in that time I have noticed a definite change in the mountain environment, specifically the conditions in the winter months. Since about the year 2000, the number of trips during the winter months where I have needed to use my ice-axe and crampons to get to the summit of a mountain seems to have reduced noticeably. This is not only due to decreased snowfall and higher temperatures, but also because several of the winters in recent years have had spells where a major thaw has occured, and it has become possible to walk to altitudes of 1000 metres and higher and encounter no snow or ice at any month of the year. This happened when I climbed Ben Starav in February recently.
This has also meant that that the snowfields that remain on the high Scottish mountain plateaux and that have traditionally made for some adventurous walking and fantastic scenery in spring and even summer have reduced and in some cases disappeared completely in recent years. My first taste of walking in the Scottish mountains was during a school trip when I was 12, walking across the large plateau from the summit of Cairn Gorm to Ben Macdui nearly 24 years ago in late June in 1983. I vividly recall the large snowfields that remained from the previous winter, and which were especially noticeable in the high corries of Cairn Toul and Braeriach several kilometres to the west and in Coire Domhain, and how they turned a summer walk into a feeling of true mountain adventure. I have visited this plateau many times since then, most recently in late June of 2006, and there seems to be less and less spring and summer snow every time I go back. A photo I took of the plateau on the June 2006 trip is here, showing Ben Macdui and Cairn Toul in the distance. Compare this to a series of photos I took of Cairn Toul and Braeriach in early May in 1995 here.
Perhaps the most striking time I visited was in mid-April 2003, when I took this photo of the northern corries from the Ptarmigan Top Station, near the summit of Cairn Gorm. This was more like the snow cover I remember from late June in 1983. In April 1990 on an adventure training course, I learned ice-axe technique on slopes near the Chalamain gap, several hundred metres lower in altitude than the northern corries in this photograph, and that were completely covered by a thick blanket of hard snow. These photos are by no means useful as scientific evidence of anything but they are certainly suggestive.
This is not something that many people disagree about and it has had a very real impact on the ability of skiing centres to operate, so a warming trend is a reality and is having an economic effect. The real question perhaps is whether it is a symptom of a longer-term trend that is only going to get worse or a natural climate cycle that will oscillate the other way eventually. There seems to be no solid consensus about this, and I am fervently hoping that proper winter conditions will return at some point (hopefully before I get too old to go hillwalking!)
Another effect that this has had is that it is now possible to walk up to the highest altitudes in the Scottish mountains, during any month of the year, with no winter equipment, and no experience of using it. It is also getting harder to find an environment in which to gain that experience (e.g. fitting crampons on a steep slope in a blizzard is really something that has to be done, not read about, and that expensive walking jacket can only really be trusted when it has endured the worst that can be thrown at it). But there are still periods when ‘traditional’ winter conditions return to the Scottish mountains, even if only for a shorter period than before, so having the right equipment and experience to cope with those conditions safely is still a necessity.
Further afield, the effects of recent climate changes are even more marked in other mountainous areas with glacial ice (which Scotland hasn’t had since potentially the 1700s, but that’s a topic for another posting), notably the Alps. Somewhere I have always wanted to go is Mount Kilimanjaro (or Uhuru Peak), not only because it is possibly the highest mountain in the word that a reasonably fit person without technical mountaineering skills can get to the top of, but also because the thought of walking amongst glacial ice at nearly 6000 metres altitude on the equator several kilometres above African plains is something that sounds like a real adventure (not to mention a great photo opportunity).
However, the glacial ice that Hemingway used as a backdrop for his famous short story may not last much longer. Recent photographs taken show a marked reduction in the extent of the summit icefields. See here, here, here and here. The reasons for this disappearance are still disputed, and some sources have noted that the ice on the summit of Kilimanjaro has been receding since the late 19th century, long before commercial aviation and cars were around to pump CO2 into the atmosphere. It’s also thought that the ice on Kilimanjaro is only 11,000 years old (considerably less than the Greenland or Antarctic ice sheets), so before then the summit was free of ice – this would indicate that the extent of the ice coverage on the summit is much more affected by natural variations in the earth’s climate rather than anything human civilization can throw at it.
This is not much comfort for me though – I want to go before the ice melts – and that will probably mean going in the next few years while I still can. There are still large icefields left, as this photo from summitpost.org that was taken just a few weeks ago shows.
A contrasting experience I had was when I attempted to climb Mount Whitney in California in late June of 2005. The previous winter had seen a large amount of snowfall, and a large snowfield stopped me from attaining the summit at an altitude of about 4000 meters, even though I had an ice-axe and in-step crampons (which weren’t all that useful). Many of the mountain roads through the Sierra Nevada passes were also still shut due to snow. There didn’t seem to be much evidence of global warming in California that year.