Has the snow climate changed in western Canadian mountains?
Climate change has been a focus for the avalanche world over the last few years, and our group has recently contributed two papers to the discussion, which we have summarised here. They both look at avalanches and how they have changed over the last 30 - 50 years. Before we get into those, let’s take a minute to explore why this is such a tricky topic, and why it is important to understand better.
So why is it tricky? There are at least three reasons as to why it is hard to find a trend amongst the noise for avalanches:
1) It is not realistic to attribute any change in avalanche activity to any one single weather factor. We all know that avalanches depend on combinations of precipitation, wind, temperature etc.
2) Avalanche activity occurs on a weather system scale of days, rather than climate scale of decades. This is further complicated by atmospheric phenomena such as El Nino or PDO. 3) Third, avalanche-related data are often incomplete, inconsistent or spread across vast geographic regions. For example, in Canada, we can go back only about 50 years for reliable written records. Unfortunately the records are usually in populated areas where there has been human interference or involvement in the natural behaviour of avalanches through explosives (mountain passes) or compaction (ski hills).
And why is it important to understand? Apart from the obvious concern we all have for the alpine environment, we also need to consider that avalanche risk assessment and mitigation techniques assume that avalanche occurrence is stationary, meaning it doesn’t change over time. We use return periods to design hazard maps, defense structures and industrial operations plans. Often these return periods are derived from historical data, which we assume won’t change into the future. Studies such as these will help us decide if changes in explosive control may be required or if the boundaries of hazard zones should be adjusted.
