Okay. We had a team out watching this glacier, and we recorded the biggest calving event that's ever been put on film.

The water comes straight from the glacier.

Drangajökull Glacier

Helicopter in front of the calving face for scale, quickly dwarfed.

The one glacier up in Greenland that puts more ice into the global ocean than all the other glaciers in the northern hemisphere combined is the Ilulissat Glacier.

Falling rocks present a danger to climbers.

A 400 foot tall calving face breaking off.

That's the retreat of this glacier.

The Godwin Austen Glacier is close to K2 in the Gilgit Baltistan region of Pakistan.

And all the way along the glacier we saw these big pools of melting ice.

We're now at the Columbia Glacier in Alaska.

This is pitched on a glacier at 17,500 feet.

This lake has been formed in the last couple of years because of the melting of the glacier.

And to the right hand side of us was this great Khumbu Glacier.

We have some cameras on the south edge of the Ilulissat, watching the calving face as it goes through this dramatic retreat.

This is a view of what's called the calving face.

The monument is a glacial cirque and is part of the El Volcán River basin.

When I meet a glacier for the very first time, what do I do?

I thought I would start with the logo. What's missing here, of course, is the North Polar ice cap.

No. It was retreating through the winter because it's an unhealthy glacier.

A mile of retreat in 75 minutes across the calving face, in that particular event, three miles wide.

The main stem, the main flow of the glacier is coming from the right and it's going very rapidly up that stem.

A glacier loses mass when the water that forms it melts.

The calving face is the wall where the visible ice breaks off, but in fact, it goes down below sea level another couple thousand feet.

It issues from the Nenana Glacier in the northern Alaska Range, southwest of Mount Deborah, approximately 100 mi (160 km) south of Fairbanks.

They actually have these buses that drive up and over the lateral moraine and drop people off on the surface of the glacier.

This glacier has doubled its flow speed in the past 15 years.

If you look in the middle background, you can see the calving face bobbing up and down like a yo yo.

The glacier can be approached via the important Balti town of Skardu.

A week before we got to the workshop, a massive landslide, caused by Hurricane Stan, last October, came in and buried 600 people alive in their village.

For India, Daulat Beg Oldie is an important outpost near the entrance to the Karakoram Pass and the Siachen Glacier region.

The block was three fifths of a mile deep, and if you compare the expanse of the calving face to the Tower Bridge in London, about 20 bridges wide.

But, in any case, the deflation of this glacier since 1984 has been higher than the Eiffel Tower, higher than the Empire State Building.

You see the glacier flowing in from the right, dropping off into the sea, camera shooting every hour.

The glacier's gone all the way up the mountain and left in its place this big lake.

This very basic shift in my physical orientation helped me shift my perspective in relation to the glacier.

The calving face is four and a half miles across, and in this shot, as we pull back, you're only seeing about a mile and a half.

That means that glacier's floating and it's unstable, and you're about to see the consequences of that floating.

To give you a little bit of a sense of scale, that calving face in this picture is about 325 feet tall. That's 32 stories.

And these cameras are positioned on rocks on the sides of the glaciers, and they look in on the glacier from permanent, bedrock positions, and they watch the evolution of the landscape.

And so this is constructed out of a heat reflected material that serves to mediate the difference in temperature between the human body and the glacial ice.

For India, the Chinese incursion also threatens its access to the 6,300 meter high Siachen Glacier, to the west of Depsang.

And once again, it's this invitation that asks people to lay down on the glacier and give it a hug.

The greatest depth of the lake is 33.3 m, and the average depth is 7.6 m. The basin of the lake was formed during the movement of the glaciers by two perpendicular channels, which expanded north to south and west to east.

It's kind of like an Andean Woodstock 60,000 Indians on pilgrimage to the end of a dirt road that leads to the sacred valley, called the Sinakara, which is dominated by three tongues of the great glacier.