Comment PARIS — Glaciers in at least a third of the World Heritage Sites that hold them, including Yosemite National Park, will disappear by mid-century even if emissions are curbed, the U.N.’s 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 the glaciers in Yosemite and ice patches in Yellowstone National Park, as well as the few glaciers that have left in Africa, they will perish. 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 warned in its report. The world’s melting glaciers are revealing their secrets very quickly About 50 of the organization’s more than 1,150 World Heritage sites have glaciers, which together make up nearly a tenth of the world’s globalized area. The nearly 19,000 glaciers located at cultural heritage sites lose more than 60 billion tons of ice a year, equivalent to the annual water consumption of Spain and France combined and accounting for about 5 percent of global sea-level rise, UNESCO said. “Glaciers are retreating at an accelerating rate worldwide,” said Tales Carvalho Resende, a UNESCO hydrology expert. The agency 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 deal with natural disasters, including floods caused by glacial eruptions. Such floods have already claimed thousands of lives and may have partly fueled Pakistan’s devastating floods this year. While there have been some local efforts to reduce melting rates – for example, by covering the ice with blankets – Carvalho Resende warned that scaling up these experiments “could be extremely difficult, because of costs but also because most glaciers are really hard to access . “ Throughout history, glaciers grew during very cold periods and shrank when those areas ended. The world’s last very cold period ended 10,000 years ago and some further natural melting was expected in Europe since the last “Little Ice Age” ended in 19th century. But as carbon dioxide emissions rose over the past century, human factors began to accelerate what was expected to be a gradual natural retreat. In Switzerland, glaciers lost a record 6 percent of their volume this year alone. While the additional melting has to some extent offset other effects of climate change — for example, by preventing rivers from drying up despite heat waves — it is quickly reaching a critical threshold, according to UNESCO. At the Forcle Glacier in Switzerland, scientists are able to discover ancient artifacts where the earth was once frozen. (Video: Rick Noack/The Washington Post) In its report, the agency writes that the peak meltwater may have already passed on many smaller glaciers, where water is now beginning to recede. If the trend continues, the agency warned, “little to no baseflow will be available during dry 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 to at least half of humanity,” said Carvalho Resende, who warned that cultural losses would also be huge. Around the world, global warming is exposing ancient artifacts faster than archaeologists can save them. “Some of these glaciers are sacred sites, which are really important to indigenous peoples 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 shared chunks of glacier ice with pilgrims, but the practice stopped when locals noticed the rapid retreat in recent years. Sign up for the latest news on climate change, energy and the environment, delivered every Thursday 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 fits with observations from researchers who have studied the retreat of glaciers. 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 actually 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 this elevation has risen several hundred meters.
