Another private jet whined overhead as I crossed the frozen lake into St Moritz. This was only a few weeks back, "pre-volcano", but as a second plume of silicate dust from Iceland's Eyjafjallajökull crater keeps many European planes grounded, it already seems a long time ago.
I was in St Moritz after riding the famous Glacier Express railway across the top of the Alps from Zermatt, an eight-hour journey through scandalously spectacular scenery. During the trip I'd passed the valley in which Europe's biggest glacier, the monstrous Aletsch, edges it's way downhill. This 27bn-tonne river of ice is, like most glaciers, shrinking as a result of global warming.
I once went to the, perhaps excessive, length of circumnavigating the world without flying as part of my own personal exploration of the relationship between travel, carbon emissions and climate change. The retreat of Aletsch was a stark reminder of that journey and the motivations behind it.