In the previous post we examined recent trends in snow and ice including glaciers and seasonal snowpack. Here we look at future projections.
I use the word projection rather than forecasts because projections explore "what-if" scenarios whereas forecasts try to predict a future outcome. For climate projections, the primary what if scenarios are often based on future greenhouse gas emissions scenarios or pathways and in some cases socioeconomic pathways. These include, for example, moderate emissions pathways in which greenhouse gas emissions peak during the mid-21st century, so-called "business as usual" scenarios in which emissions increase through the 21st century, and others.
These scenarios produce increases in globally average temperature over pre-industrial values. For instance, the moderate-emissions scenario produces an increase of about 2°C and the high-emissions scenario produces an increase of about 4°C. These are sometimes referred to as global warming levels (GWL) and I'll be using those for this post. For a given global warming level, the amount of warming for a region may differ from the global average and in the case of Austria (and Utah) the amount of warming is greater.
We will start with glaciers in the European Alps based on work presented by Zekollari et al. (2019). If interested, I have a deeper dive on this topic (see The Fate of Alpine Glaciers). The graph below presents the recent (prior to 2017) and projected future volume of glacier ice in the Alps, the latter under four scenarios. One is the committed loss, which is an estimate of the future loss of glacier volume if the climate stabilized around what occurred from 1988-2017. The others are with an additional levels of global warming.
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| Source: Zekollari et al. (2019), with annotations added |
Because the Alpine glaciers are currently out of equilibrium with the rapid warming that has occurred in recent decades, they will continue to shrink even if the climate remains unchanged relative to 1988–2017. Under such a scenario, the volume fraction of glacier ice would decline about 40% from 2017 levels. Increasing amounts of glacier loss occur for higher global warming levels. Under high global warming levels, nearly all of the glacier ice in the Alps is gone by 2100 (see red line) with the only glacier remnants remaining in the high terrain region from Mt. Blanc to Zermatt and the Swiss Jungfrau.
Moving to snowfall, below are estimated changes (from 1981–2010 to 2070–2099) in the water-equivalent of snowfall for the Alpine region (September to May) as a function of elevation under a global warming level of ~2°C and a global warming level of ~4°C. Similar to recent trends, declines are very much elevation dependent and largest in the lower elevations and smallest in the upper elevations. For the 1000-1250 m elevation band, the various models call for declines of 15-40% for 2°C of global warming and 40–60% for 4°C of global warming. Declines are larger at lower elevations and smaller at upper elevations.
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| Source: Frei et al. 2018, with annotations added. |
Another perspective is provided by trends in the number of days with at least 30 cm of snow on the ground. The graph below is now for the Austrian Alps, which are a bit colder at a given elevation than the western Alps and the Italian Alps. Again, the percentage changes are elevation and scenario dependent. For the 1500-2000 m elevation range, snow cover of at least 30 cm persisted for about 175 days a year. For 1991-2000, this has declined to about 130. For a global warming level of 2°C, that drops to about 110 days with additional declines for larger global warming levels. At upper elevations, the percentage declines are smaller, but there are still declines.
Finally, groups have estimated changes in ski resort snow reliability based on projections like those above but also considering changes in snowmaking conditions and projected advances in snowmaking capacity. In the case of Austria, the regions that see the largest declines in snow reliability, especially under a high-emissions scenario (right figure below), are in eastern Austria (the Austrian States of Lower Austria, Upper Austria, and Styria) and the northern Alpine Rim in western Austria near the German border. These are areas where ski resorts are at low-to-moderate elevations.
The highest snow reliability persists in the inner Alps in western Austria near the Italian border where the terrain is high (green ellipse), and in the Arlberg region in western Austria near the border between the Austrian states of Voralberg and Tyrol (red ellipse). In the case of the former, there are several resorts with substantial terrain above 2000 meters (Kaunertal, Pitztal, Sölden, Obergurgl, Ischgl), whereas the latter is currently Austria's snowiest region and will likely maintain some level of snow reliability even as a greater fraction of wintertime precipitation falls as rain instead of snow. This does not mean those regions will not see declines in natural snow reliability and hours with favorable snowmaking conditions, but that they are more resilient to warming given their elevation or more abundant natural snowfall. Everywhere will experience the pain of global warming, but the "competitive advantages" of these regions will increase with time as other regions suffer more.
We will see similar effects in Utah as the high-elevation, snow-abundant terrain around Little Cottonwood Canyon suffers less than lower elevation regions in the Wasatch. High elevation (and north facing) resorts like Alta and Snowbird will see an increasing competitive advantage in the future, as was evident this past season.
What I takeaway from this and other research is that there still will be snow and snowstorms in the future, although we can expect downward trends in snowfall and snow-cover duration in most regions. The size of the decline, however, is strongly dependent on the amount of warming, which is tied to future greenhouse gas emissions. Thus, the fate of snow and skiing are ultimately in our hands.
