Other glaciers can be saved only if greenhouse gas emissions “are drastically reduced” and global warming is limited to 1.5 degrees Celsius, the Paris-based UNESCO warned in its report.
“This report is a call to action,” UNESCO director-general Audrey Azoulay said in a statement, linking the report to the upcoming climate change conference in Egypt. “COP27 will play a crucial role in helping to find solutions to this problem.”
About 50 of the organization’s more than 1,150 World Heritage sites have glaciers, which together make up almost a tenth of the world’s glacier-covered area.
The almost 19,000 glaciers located in heritage sites are losing more than 60,000 million tons of ice a year, which is equivalent to the annual water consumption of Spain and France combined, and represents about 5 percent of global sea level rise, UNESCO said.
“Glaciers are retreating at an accelerating rate all over the world,” said Tales Carvalho Resende, a UNESCO hydrology expert.
The organization described a “warming cycle” in which melting glaciers cause darker surfaces to appear, which then absorb even more heat and accelerate ice retreat.
In addition to drastic cuts in emissions, the UNESCO report calls for better monitoring of glaciers and the use of early warning mechanisms to respond to natural disasters, including floods caused by glacial lake outbursts. Such floods already cost thousands of lives and may have partly fueled Pakistan’s catastrophic floods this year.
While there have been some local attempts to reduce melt rates, for example by covering the ice with blankets — Carvalho Resende warned that scaling up such experiments “could be extremely challenging, because of costs, but also because most glaciers are very difficult to access.”
Throughout history, glaciers grew during very cold periods and shrank when those periods ended. The world’s last very cold period ended more than 10,000 years ago, and some additional natural melting was expected in Europe after the last “Little Ice Age” ended in the 19th century.
But as carbon dioxide emissions increased over the past century, human factors began to speed up what was expected to be a gradual natural retreat. In Switzerland, glaciers lost a record 6 percent of their volume this year alone.
While additional melting has to some extent offset other impacts of climate change, for example keeping rivers from drying up despite heat waves, it is fast reaching a critical threshold, according to UNESCO.
In its report, the organization writes that peak meltwater may have already passed in many smaller glaciers, where the water is now starting to recede.
If the trend continues, the organization warned, “there will be little or no base flow available during dry periods.”
The changes are expected to have important ramifications for agriculture, biodiversity and urban life. “Glaciers are crucial sources of life on Earth,” UNESCO wrote.
“They provide water resources to at least half of humanity,” said Carvalho Resende, who warned that cultural losses would also be immense.
Around the world, global warming is exposing ancient artifacts faster than they can be saved by archaeologists.
“Some of these glaciers are sacred places, which are really important to indigenous people and local communities,” he said.
UNESCO cited the example of the centuries-old Snow Star Festival in the Peruvian Andes, which has already been affected by ice loss. Spiritual leaders once covered the glacier’s ice blocks with pilgrims, but the practice stopped when locals noted the rapid retreat in recent years.
The small glaciers at low or medium altitude will be the first to disappear. UNESCO said rates of ice loss from small glacial areas “more than doubled from the early 2000s to the late 2010s”.
This matches the observations of researchers who have studied glacial retreat. Matthias Huss, a European glaciologist, said scientists had seen “very strong melting in the last two decades” in Switzerland.
At the same time, there are fewer and fewer places cold enough for glaciers to grow. “Today, the limit where glaciers can still form new ice is about 3,000 meters. [about 9,840 feet]”, he said, explaining that in recent decades that altitude has risen several hundred meters.
