The effects of climate change have once again manifested in much more tangible ways.

This was shown in a rather disconcerting series of photos captured by two mountaineers in the French Alps.

Lake formed where there should only be snow

Bryan Mestre, an avid mountaineer and rock climber, posted two photos of the Dent du Géant mountain in France and Italy on his Instagram @bryanthealpinist.

Mestre apparently first spotted a crystal blue lake at the base of Dent du Géant, 3,400 metres high in altitude on the Mont Blanc massif, the highest mountain region in the Alps and Western Europe.

However, what is most shocking about this find was that the lake wasn't always there.

According to Mestre, the pool of water had reportedly formed in just 10 days time.

A photo previously taken by fellow mountaineer Paul Todhunter showed the mountainscape completely covered in snow.

Here's what the mountain looked like before:

And what it looked like only 10 days later on June 28, 2019 when Mestre took the photo of the lake.

More ice has clearly melted, exposing more of the rock structure beneath.

The lake isn't as small as it seems either—according to National Geographic France, it measured approximately 10 metres wide and 30 metres long.

View this post on Instagram

To all the people claiming it was a fake or a photoshopped picture, a false flag or whatever... It’s very real, the glacier is in terrible shape and liquid water only accelerates the melting process... There’s now a lake at the base of Dent du Géant and Aiguilles Marbrées.... Keep sharing! Thank you to my sponsor @barrabes.ski.mountain who supports me and allows me to keep on exploring! #climbing #climber #climb #frenchalps #savoie #savoiemontblanc #hautesavoie #outdoors #globalwarming #mountaineering #mountains #mountain #montagne #montagna #montaña #montanhismo #mountaineer #alpinist #alpinism #alpinisme #alpinismo #alpi #alps #alpes #environment #savetheplanet #climatechange #montblanc @beal.official @millet_mountain @patagonia @blueiceclimbing

A post shared by Bryan Mestre (@nomad__tactical) on Jun 30, 2019 at 6:59am PDT

Mestre, equally baffled, stated in his Instagram caption that "this is the first time anything like that has ever happened".

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Time to sound the alarm... The problem here? These two pictures were taken only 10 days apart... It was taken earlier on June 28th, the second one was shared by Guide Mont Blanc Only 10 days of extreme heat were enough to collapse, melt and form a lake at the base of the Dent du Géant and the Aiguilles Marbrées That I know, this is the first time anything like that as ever happened. Southern Europe and the Alps have been struck by a massive heatwave with temperature ranging from 40 to 50 degrees, the below 0 freezing altitude was as high as 4,700m (15,400ft) and during the day temperatures as high as 10 degrees Celsius (50 F) were felt on top of Mont Blanc 4,810m (15,780ft)... This is truly alarming glaciers all over the world are melting at an exponential speed... Photo Credit : Gianlunca Marra (@guidemontblanc ) Thank you to my sponsor @barrabes.ski.mountain who supports me and allows me to keep on exploring! #climbing #climber #climb #frenchalps #savoie #savoiemontblanc #hautesavoie #outdoors #globalwarming #mountaineering #mountains #mountain #montagne #montaña #montagna #montanhismo #mountaineer #alpinist #alpinism #alpinisme #alpinismo #alpi #alps #environment #savetheplanet #climatechange #montblanc @patagonia @beal.official @millet_mountain @blueiceclimbing

A post shared by Bryan Mestre (@nomad__tactical) on Jun 30, 2019 at 3:10am PDT

Heatwave in France

Lakes are a rare occurrence this high up, and Mestre has attributed its formation to the massive heatwave Europe is currently experiencing.

"Only 10 days of extreme heat were enough to collapse, melt and form a lake at the base of the Dent du Géant and the Aiguilles Marbrées."

In the last week of June, the various parts of the continent experienced scorching temperatures of up to 40ºC.

And France has not been spared.

The day when Mestre took the photo of the lake also saw temperature in France hitting a record-breaking 45.9ºC, reported IFLScience.

The previous highest record was 44.1ºC in 2003.

Meanwhile, the Mont Blanc region in the Alps where the lake was found, experienced temperatures 9.3ºC on June 29.

Additionally, the isotherm (freezing point) usually hovers around the 3,000-meter line at the Mont Blanc, said Mestre.

However, in that period, the isotherm had risen to an altitude of 4,700m instead, meaning that ice below that level would melt.

Mestre said to IFLScience that liquid water is an abnormality at such high altitudes. As an experienced mountaineer, he also stated that even "during the hottest days, you may find snow melting, but that's it."

"It's located in the 3,400 to 3,500-meter area. You're supposed to find ice and snow at this altitude, not liquid water. Most of the time when we stay for a day at this altitude, the water in our water bottles starts freezing.”

Top photo from Bryan Mestre/Instagram