Posted on 27 June 2023 by John Mason, BaerbelW

On February 14, 2023 we announced our Rebuttal Update Project. This included an ask for feedback about the added "At a glance" section in the updated basic rebuttal versions. This weekly blog post series highlights this new section of one of the updated basic rebuttal versions and serves as a "bump" for our ask. This week features "Are glaciers growing or retreating?". More will follow in the upcoming weeks. Please follow the Further Reading link at the bottom to read the full rebuttal and to join the discussion in the comment thread there.

At a glance

Glaciers are wonderful things, as any high mountain-climber will agree. Trekking up a glacier at sunrise to reach the start of a climb is one of the truly awesome experiences in mountaineering. They also act as vast cold-storage facilities, capturing and holding winter snowfall. People, animals and crops in the valleys below benefit from this meltwater supply when the warmer season arrives. That makes them really important. So let's take a look at what makes glaciers tick.

Glaciers form when perennial snow-cover starts building up, year upon year. Freeze-thaw cycles and compaction gradually turn the accumulated snow into glacial ice. The process takes years and for the glacier to survive, conditions need to remain cold, with a continual ample supply of new snow, year in year out, over the decades.

Because a glacier is a slow-moving river of ice with its motion driven by gravity, it will typically exhibit a distinctive set of physical features. There will be the break-line along which it pulls away from its headwall. This is marked by a system of large crevasses that divide the moving ice below from the static ice above.

Crevasses also form in the moving part of the glacier where the ice undergoes flexure and splits. Such features are commonest where a glacier is flowing over uneven ground or is rounding a bend. Where a glacier encounters a major steepening in its downhill course, it will break up into a chaotic system of unstable, crevasse-bounded blocks known as an ice-fall.

For a glacier to be stable, snowfall needs to be in balance with 'ablation'. Ablation is the term that covers the ways in which a glacier loses its snow and ice. If the glacier is going to endure, snow gain clearly has to be at least equal to ablation. Forms of ablation include surface melt, meltwater run-off, strong winds blasting snow away, sublimation (solid to vapour direct transition) and avalanches. In addition, ablation can also occur within and beneath a glacier. When meltwater is running along beneath the ice, it acts as a lubricant, so the glacier's flow may suddenly speed up, or surge, as it's called.

With any glacier, its status in terms of whether it is gaining or losing mass is termed its 'mass balance'. Mass balance is a mathematical expression of whether a glacier is retreating or advancing. It is based on various careful and long established measurement techniques, Unfortunately, mass balance measurements tell us that a very high percentage of Earth's mountain glaciers are in retreat. It is wrong to single out the few glaciers that are growing in the face of the overall trend of steep decline, in order to argue there is no global warming. It's the scientific sin of cherry-picking.

Please use this form to provide feedback about this new "at a glance" section. Read a more technical version via the link below!

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In case you'd like to explore more of our recently updated rebuttals, here are the links to all of them: