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PARIS — Glaciers in at least a third of World Heritage sites, including Yosemite National Park, will disappear by mid-century even if emissions are curbed, the UN Educational, Scientific and Cultural Organization warned in a new report on Thursday.
Even if global warming is limited to just 1.5 degrees Celsius (2.7 degrees Fahrenheit), which now seems unlikely, all of the glaciers in Yosemite and the ice patches in Yellowstone National Park and the few glaciers that remain in Africa will , get lost.
Other glaciers can only be saved if greenhouse gas emissions are “drastically reduced” and global warming is limited to 1.5 degrees Celsius, Paris-based UNESCO warns in its report.
The world’s melting glaciers are giving up their secrets too quickly
About 50 of the organization’s more than 1,150 World Heritage Sites have glaciers, which together make up almost one-tenth of the world’s glaciated area.
The nearly 19,000 glaciers at heritage sites are losing more than 60 billion tons of ice annually, equivalent to the annual water consumption of Spain and France combined and accounting for about 5 percent of global sea level rise, according to UNESCO.
“Glaciers are retreating faster and faster around the world,” said Tales Carvalho Resende, a UNESCO hydrology expert.
The organization described a “warming cycle” in which melting glaciers create darker surfaces, which then absorb even more heat and accelerate ice retreat.
In addition to drastic emission reductions, the UNESCO report calls for better monitoring of glaciers and the use of early warning mechanisms to respond to natural disasters, including flooding from bursting glacial lakes. Such floods have already claimed thousands of lives and may have partly fueled Pakistan’s disastrous 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 expanding these experiments “could be extremely difficult because of cost reasons, but also because most glaciers are really difficult to access.” are. ”
Throughout history, glaciers have grown during very cold periods and shrunk at the end of those stretches. The world’s last very cold period ended over 10,000 years ago, and further natural melting was expected in Europe after the last “Little Ice Age” ended in 19th century.
But as carbon emissions spiked over the past century, human factors began to accelerate what had been expected to be a gradual natural retreat. In Switzerland, glaciers have lost a record-breaking 6 percent of their volume this year alone.
While the additional melting has partially offset other impacts of climate change — for example, preventing rivers from drying up despite heat waves — it is quickly reaching a critical threshold, according to UNESCO.
In the Forcle Glacier in Switzerland, scientists can discover ancient artifacts where the land was once frozen. (Video: Rick Noack/Washington Post)
In its report, the organization writes that peak meltwater may have already passed on many smaller glaciers, where the water is now beginning to recede.
If the trend continues, the organization warned, “little to no bottom flow will be available during the drier periods.”
The changes are expected to have significant impacts on agriculture, biodiversity and urban life. “Glaciers are critical sources of life on earth,” UNESCO wrote.
“They provide water resources for at least half of humanity,” said Carvalho Resende, who warned that the cultural losses would also be immense.
Around the world, global warming is uncovering ancient artifacts faster than archaeologists can save them.
“Some of these glaciers are sacred sites that are really important to indigenous peoples and local communities,” he said.
As an example, UNESCO cited the centuries-old Snow Star Festival in the Peruvian Andes, which is already suffering from ice loss. Spiritual leaders once shared blocks of glacial ice with pilgrims, but the practice stopped when locals noticed the rapid decline in recent years.
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Small glaciers at low or medium altitudes will be the first to disappear. UNESCO said rates of ice loss in small glaciated areas “more than doubled from the early 2000s to the late 2010s.”
This is consistent with observations made by researchers studying retreating glaciers. Matthias Huss, a European glaciologist, said scientists had seen “very strong melting over the past two decades” in Switzerland.
At the same time, there are fewer and fewer places cold enough for glaciers to actually grow. “Today, the limit where glaciers can still form new ice is around 3,000 meters [about 9,840 feet]’ he said, explaining that this height has increased by several hundred meters in recent decades.