As the UN prepares its report on the fate of the world’s ice, Adam Vaughan visits the dramatically changing landscape of Mer de Glace near Mont Blanc

The Mer de Glace glacier Katie Moore for New Scientist

“IT’S very fast. We are confronted with the reality of the retreat,” says glaciologist Luc Moreau about the rapidly vanishing ice at France’s biggest glacier. We are looking at the unmistakeable fingerprint of climate change as told by the historical photos hanging in a hotel overlooking the Mer de Glace, the “sea of ice” near the Alps’ highest summit, Mont Blanc.

About a century ago, women with boaters and parasols sat near the Montenvers train station above the glacier, which then was almost level with a tongue of jagged ice snaking into the distance. Today, visitors are greeted by a slightly sad and largely grey glacier that is about 100 metres lower.

From the station, a short trip by cable car takes me to the height where, in 1988, a visitor could descend down three steps to reach the glacier. There are 580 steps down to the glacier now. Of these, 80 were added this year – a stark illustration of the accelerating effects of global warming.

The fate of the world’s glaciers will be laid bare by the UN climate science panel on 25 September, just days after research is expected to confirm that the extent of Arctic sea ice this summer reached the second lowest level ever recorded.

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There are some 170,000 glaciers worldwide covering an area of about 730,000 square kilometres. Monitoring of 500 glaciers globally shows they are retreating across the board and, since 1960, the rate at which they are losing ice has increased. A leaked draft of a report from the Intergovernmental Panel on Climate Change (IPCC) on our planet’s oceans and ice warns that, this century, melting glaciers will “first give too much water and then too little”.

“France’s two largest glaciers have both lost 800m of their lengths over the past 30 years”

Many places mentioned in the IPCC report will seem remote to some people, but the Mer de Glace and nearby Argentière glacier are in the heart of Europe, next to Chamonix, a holiday destination visited by millions every year.

Tourists can see the effects clearly. The steps down to the Mer de Glace are punctuated by “level of the glacier” signs from 1985 through to 2015, the year the world agreed the Paris accord to avert dangerous global warming.

Steps lead down to the Mer de Glace glacier Katie Moore for New Scientist

At the ice cave carved in the glacier, white sheets have been laid atop the ice to slow the melting. Sébastien Payot tells me he is running out of ways to adapt. Since 1946, his family’s business has carved a cave here for tourists every year. But this year, the diggers encountered a spit of rock, indicating that they are nearing the bottom of the glacier. He fears that the ice’s retreat means next year’s cave will be the last. “It’s a barometer of global warming,” he says.

An ice cave is dug in the glacier every year Katie Moore for New Scientist

Recent measurements by Christian Vincent of the University of Grenoble show that the Mer de Glace and Argentière glacier, France’s second greatest glacier, have both lost around 800 metres in length in the past three decades. Researchers have gone further back in time by working out the glacier’s depths using photos taken from a balloon in the early twentieth century, and comparing them with photos taken from a helicopter more recently (see pictures below).

Aerial shots of the Mer de Glace glacier from 1919 and 2019 reveal how much ice has been lost Left: Walter Mittelholzer, ETH-Bibliothek Zürich; Right: Kieran Baxter, University of Dundee

The lift and the steps down to the shrinking glacier will soon be dismantled if plans by ski-lift firm Compagnie du Mont Blanc go ahead. It hopes to move access to the glacier 500 metres up the valley, and build an educational centre focused on climate change. “It should allow us to dig a new cave in a place where scientists think there should still be some ice in the next 20 years, even with the most pessimistic scenarios,” says Mathieu Dechavanne at Compagnie du Mont Blanc.

In this area, mountaineers are seeing the changes up close. “Eighteen years ago, people used to ask ‘have you seen evidence of climate change?’ They don’t ask that anymore, because it’s clear there is,” says Andy Perkins, a British mountain guide who has guided climbers here since 2001.

Warming is leading to more rockfall and thawing permafrost, causing havoc with infrastructure, he says. “You have to take greater care because there is no normal anymore,” says Perkins.

In August, Perkins took a client on the Cosmiques Arête, a route above Chamonix that is considered stable. A day later, a large piece of rock fell from it. A recent study of 95 Mont Blanc massif climbing itineraries from a famous 1973 book found that all but two of the routes have been affected by climate change.

Becky Coles, part of an all-female team midway through climbing all the 4000-metre peaks in the Alps, found the heatwave in June closed several route options. It is hard to show rockfall is getting worse because of a lack of data, she says, but it feels worse than in the past. “I think there’s more rockfall, without a doubt.” The heatwave was made more probable by climate change.

The retreat of the glaciers is affecting flora and fauna too, says Hillary Gerardi of the Research Centre for Alpine Ecosystems in Chamonix. “We are seeing the productivity of vegetation going way up, plants are moving up the slope and the growing season is getting longer,” she says, citing the example of a large tree that was found growing above Chamonix where a glacier had been situated just a decade ago.

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Another example comes from the keeper of the Vignettes hut, a stop on a popular walking route in the area. A local plant known as génépi, used to make an alcoholic drink, is usually picked at about 2400 metres above sea level. This year, the keeper picked it at 3100 metres, the highest so far. Meanwhile, some species will lose out, like the rock ptarmigan, a bird whose Alps habitat is shrinking.

The world is currently on the path to dangerous warming, but on 23 September, some 60 heads of state are expected to present new climate change plans at a UN summit in New York. The UN special climate envoy, Luis Alfonso de Alba, says the European Union’s contribution will be fundamental to the meeting’s success.

Unless global action is taken to curb carbon emissions, France’s two greatest glaciers are doomed. A recent study by Vincent shows that on the current emissions trajectory, Argentière will be gone by 2080 and Mer de Glace by the end of the century. “Almost nothing” can be done locally to stop their decline, he says. Their future rests on the course the world takes.

We corrected the year the historical picture of the glacier was taken and the spelling of photographer Katie Moore’s name