Where global warming gets real: inside NASA’s mission to the north pole

From the window of a NASA aircraft flying over the Arctic, looking down on the ice sheet that covers most of Greenland, it’s easy to see why it is so hard to describe climate change. The scale of polar ice, so dramatic and so clear from a plane flying at 450 metres (1,500ft) – high enough to appreciate the scope of the ice and low enough to sense its mass – is nearly impossible to fathom when you aren’t sitting at that particular vantage point.

But it’s different when you are there, cruising over the ice for hours, with NASA’s monitors all over the cabin streaming data output, documenting in real time – dramatising, in a sense – the depth of the ice beneath. You get it, because you can see it all there in front of you, in three dimensions.

Imagine a thousand centuries of heavy snowfall, piled up and compacted into stone-like ice atop the bedrock of Greenland, an Arctic island almost a quarter the size of the US. Imagine all of modern human history, from the Neolithic revolution 12,000 years ago – when humans moved from hunting and gathering to agriculture, and from there, eventually, to urban societies – until today. All of the snow that fell on the Arctic during that entire history is gathered up in just the top layers of the ice sheet.

Imagine the dimensions of that ice: 1.71m sq km (656,000 sq miles), three times the size of Texas. At its belly – from the top layer, yesterday’s snowfall, to the bottom layer, which is made of snow that fell out of the sky 115,000-130,000 years ago – it reaches 3,200 metres (10,500ft) thick, nearly four times taller than the world’s highest skyscraper.

Imagine the weight of this thing: at the centre of Greenland, the ice is so heavy that it warps the land itself, pushing bedrock 359 metres (1,180ft) below sea level. Under its own immense weight, the ice comes alive, folding and rolling in solid streams, in glaciers that slowly push outward. This is a head-spinningly dynamic system that we still don’t fully understand – and that we really ought to learn far more about, and quickly. In theory, if this massive thing were fully drained, and melted into the sea, the water contained in it would make the world’s oceans rise by 7 metres (23ft).

When you fly over entire mountain ranges whose tips barely peek out from under the ice – and these are just the visible ones – it’s possible to imagine what would happen if even a fraction of this quantity of pent-up freshwater were unleashed. You can plainly see how this thing would flood the coasts of the world, from Brooklyn to Bangladesh.