A CHANGING WORLD
“Swiss glaciers, they lost about 10 percent of their volume in only two years, so the situation is really dramatic.” Stefan Uhlenbrook, Director of Hydrology, Water and Cryosphere at the World Meteorological Organization (WMO)
Annual global glacier mass changes, 1976-2023
Glacier mass change (gigatonnes): Negative values refer to ice loss while p ositive values refer to ice gain
-602
0
139
Source: C35/ECMWF/WGMS; Data – WGMS
In just a few seconds, rock and ice completely buried Blatten, destroying houses that had stood for centuries and, quite literally, wiped the town from the map. Before and after photos hardly seem like they were taken from the same place; only a few buildings and roads remained untouched. For all the destruction the Swiss glacier caused, only one death was recorded, a local shepherd who was outside the evacuation zone. The rest of the town of about 300 had fled to safety when it became clear that the Birch Glacier may not be entirely stable. Places without early warning systems, evacuation procedures or adequate protective infrastructure rarely fare as well. A melting glacier is not like an ice cube melting on the ground, which expands evenly. Glaciers often hold back huge
amounts of water and rock, so when they lose structural integrity they can quickly cause problems many miles away. For example, glacier lakes are a common, and picturesque, sight in the mountains. Yet like a bathtub slowly filling with water until it spills over, global warming and glacier melt create an ever-increasing risk that these lakes will spill over onto nearby communities. According to a 2023 estimate, 15 million people worldwide are at risk from these glacial lake “outburst” floods. “The changes we are making to our planet are increasing our collective risk,” said Jenty Kirsch-Wood, Head of Global Risk Management and Reporting at the United Nations Office for Disaster Risk Reduction. “As that risk is increasing, it is essential that we invest in better hazard monitoring.”
Monitoring every glacier in every country is an expensive endeavor and history is filled with stories of how quickly things can go wrong if there is no way to tell if danger is on its way, whether it is a slow drip or a force majeure. In 1941, a block of ice broke off from Peru’s Palcaraju mountain and fell into Lake Palcacocha. The resulting outburst flood killed at least 1,800 people and destroyed a third of the city of Huaraz. It only took the water 15 minutes from the initial crack of ice until the water reached the city. “The black water did not slide, but formed huge, inarticulate, boiling waves. Dense dust covered the scene. The sight was Dantesque,” a survivor later told an author researching the incident. “When I turned my face, my mother had disappeared.”
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