Glaciers worldwide are retreating.
Of the 250 alpine glaciers studied, the Taku Glacier in Alaska was the only stable glacier – until 2019, when it also began to retreat. At 1,500 metres thick, it’s one of the world’s thickest mountain glaciers, now retreating by up to 390 billion tons of snow and ice a year.
(This is a big deal. Mighty glacier finally succumbs to climate change: The Age: 8 Nov 2019)
The glacier altitude feedback cycle
This feedback occurs because the average temperature at the top of a mountain is lower than at sea level, and this is relevant because we have some thick ice sheets, for example:
- up to 4,900 meters deep in Antarctica,
- up to 3,000 metres in Greenland, &
- up to 1,500 meters for mountain glaciers.
In this amplifying feedback cycle:
- more glacial surface melting tends to cause
- a drop in the altitude of the glacial surface, which tends to cause
- higher temperatures at these lower glacial surfaces, which tends to cause
- more glacial surface melting, and then the cycle repeats.
This feedback cycle indirectly increases global temperatures as it (1) decreases the area of reflective glacial ice, and so (2) increases the absorption of the sun’s energy and (3) warms the planet.
The Dangers of Glacial Melting
- Glacial Outburst Floods: Melting ice forms unstable glacial lakes that can suddenly burst without warning. These Glacial Lake Outburst Floods (GLOFs) can be destructive, as seen in the devastating floods in Nepal in August 2026. They can also drive increasingly severe annual flooding. This is happening in Juneau, Alaska’s capital.
(Nepal’s Glacier Time Bomb: ABC Radio Podcast: If You’re Listening: September 2026)
- Freshwater Depletion: Glacial retreat directly threatens to reduce flows in some major river systems, including the Ganges in Asia and the Colorado River in North America. Millions of people who rely on these waterways face shrinking water supplies for drinking, crop irrigation, and hydroelectric power.
- Extreme Sea-Level Rise: Melting ice sheets in Greenland and Antarctica pose a severe long-term threat to global coastlines. Rising sea levels threaten to submerge major coastal cities, displace populations, and destroy critical infrastructure worldwide.
The Extreme Ice Survey
The Extreme Ice Survey collects visual evidence of global warming’s impact on our planet, such as time-lapse photos of glacier contraction. Excluding Antarctica, 95% of the world’s glaciers are retreating. See:
- the film “Chasing Ice”, produced in cooperation with National Geographic. It won an Emmy Award as an outstanding nature program, or
- the TED talk by James Balog in July 2009.
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Loaded May 2015: Modified 6 September 2026