(Bloomberg) -- France’s largest glacier once looked so mighty sliding down the granite slopes of the Mont Blanc, Western Europe’s tallest peak, that early explorers struggled to find the words to capture it.
“You must imagine your lake put in agitation by a strong wind, all frozen at once,” wrote British adventurer William Windham, one of the first tourists to explore the glacier in 1741. “Perhaps even that would not produce the same appearance.”
That description gave the place its current name—la Mer de Glace, the Sea of Ice. At that time and until the late 1980s, thousands of years of ice covered the steep valley. Visitors walked from the nearby town of Chamonix to Montenvers, where the glacier was so close they only had to hike down a few meters to touch it.
Today, the Mer de Glace remains the biggest glacier in France, and the second-largest in the Alps. But it’s also become a symbol of the rapid pace of global warming. Mont Blanc is heating up more than twice as fast as the rest of the world. The Mer de Glace has been shrinking since the beginning of the 20th century, but the loss has accelerated over the past two decades. Since 1900, it’s shrunk by about a third of its volume. In total it’s lost around 1.5 cubic kilometers of ice. That's equivalent to more than half a million Olympic swimming pools of ice.
“Glaciers are symbols of climate change because they’re the elements in nature that react fastest to it,” says French glaciologist Luc Moreau. “Solar radiation, temperature, and greenhouse gases are all invisible things, but measuring glaciers gives us information of all of them.”
Glaciers go through melting and freezing cycles, losing mass in warm weather and gaining it back once the temperature drops. When Moreau arrived in Chamonix in 1987, the Mer de Glace was able to recover much, if not more of its volume over the winter. Now it just shrinks.
Regardless of how much the planet warms, glaciers in the Alps will lose about half their 2017 volume by 2050, according to Harry Zekollari, a glaciologist at the University of Technology Delft, in the Netherlands. If humans keep emitting greenhouse gases at our current pace, glaciers in the Alps will lose about 90% of their volume by the end of the century, according to a model he and others developed using data from the Alps’ 4,000 glaciers. If emissions are brought in line with the Paris climate agreement goal of limiting warming below 2° Celsius by the end of this century, they’ll lose about two-thirds. “We’ll be the ones to determine if there’s still ice left on the European Alps by the end of this century or not,” Zekollari says.
For decades Chamonix has been considered the world capital of alpinism. Some of the world’s most famous mountaineers learned climbing and ice walking on the slopes of Mont Blanc. On any given night last year, the Aubergne-Rhône-Alpes region to which Chamonix belongs hosted more than 440,000 visitors—although of course the actual number of visitors fluctuates seasonally, and might have been much higher in certain months. Half the people who traveled there did so for the winter sports, and they spent an estimated 21 billion euros ($24.7 billion), according to the region’s tourism authority.
Today’s visitors catch a little red train from Chamonix to Montenvers, where they’re treated to a view of the iceless valley floor, a gray plain that another glaciologist, Jean-Baptiste Bosson, describes as a “pebble lake.” Tourists who want to see the glacier itself must descend a set of steep metallic steps to reach a grotto carved into the ice. As the Mer de Glace retreated deeper into the valley, new grottos had to be carved, and more steps had to be added. There were three steps total in 1988; 118 by 2000. Today there are more than 500, with more being added all the time.
Among those feeling the effects of these changes firsthand is the Compagnie des Guides de Chamonix, the first organization to turn mountain guiding into a formal profession almost 200 years ago. Olivier Greber, the president of the Compagnie, says he remembers the days when it was possible to ski down the glacier, the famous Vallée Blanche descent, to the bottom of the valley and reach the Montenvers train station without taking your skis off. Now, the same descent requires a 15-minute walk across rocks that have been ground down by the glacier.
He and the other guides have adapted their routes to avoid areas covered by increasingly delicate frozen ground known as permafrost, and have become used to answering questions from visitors on climate change. “There’s sometimes a certain anxiety of seeing the Mer de Glace before it disappears,” Greber says. That kind of tourism isn’t necessarily bad, he says. “Awareness is important because we can’t protect things that we don’t love.”
Still, he says, he’s confident Chamonix and the Mer de Glace region will remain an attractive destination.
“We lived through a golden period in which we imagined we had something that would never change,” Greber says. “It is in fact changing, but we will continue to adapt.”
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