A Global Warning

By: Daniel Schorn

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International Atomic Energy Agency chief Yukiya Amano, left, shakes hands with Iran's chief nuclear negotiator Saeed Jalili in Tehran, Iran, May 21, 2012. (AFP/Getty Images)

60 Minutes got a bird's-eye view of how unstable the ice is becoming on a flight with glaciologist Carl Boggild.

Boggild anchored 10 research stations to the ice. But every time he comes to visit, the ice and his stations have moved.

Flying over the ice, Pelley noticed lots of fissures and crevices breaking through the ice.

Asked what causes this, Boggild explained, "This is actually the ice flow, where you have so much tension in the ice that it cannot stick together. And it breaks and opens a crevice which goes about 150, 200 feet down."

The ice is also melting on the sides, Boggild says.

High overhead, Pelley remarked that one could hear the water running.

"It's like a small river," Boggild said.

A leading theory says those little rivers lubricate the bottom of the ice sheet, helping it move off the bedrock and out to sea.

And there may be no stopping it. Arctic warming is accelerating. It's a chain reaction. As snow and ice melt they reveal dark land and water that absorb solar heat. That melts more snow and ice, and around it goes.

There's long been a debate about how much of this is earth's naturally changing climate and how much is man's doing. Paul Mayewski, at the University of Maine, says the answer to that question is frozen inside an ice core from Greenland.

With funding from the National Science Foundation, Mayewski has led 35 expeditions collecting deep ice cores from glaciers. The ice captures everything in the air, laying down a record covering half a million years.

"We can go to any section of the ice core, to tell, basically, what the greenhouse gas levels were; we can tell whether or not it was stormy, what the temperatures were like," Mayewski explains.

60 Minutes brought Mayewski back to Greenland, where he says his research has proven that the ice and the atmosphere have man's fingerprints all over them.

Mayewski says we haven't seen a temperature rise to this level going back at least 2,000 years, and arguably several thousand years.

As for carbon dioxide (CO₂) levels, Mayewski says, "we haven't seen CO₂ levels like this in hundreds of thousands of years, if not millions of years."

What does that tell him?

"It all points to something that has changed and something that has impacted the system which wasn't doing it more than 100 years ago. And we know exactly what it is. It's human activity," he says.

It's activity like burning fossil fuels, releasing carbon dioxide and other greenhouse gases. The U.S. is by far the largest polluter. Corell says there's so much greenhouse gas in the air already that more temperature rise is inevitable.

Even if we stopped using every car, truck, and power plant — stopping all greenhouse gas emissions — Mayewski says the planet would continue to warm anyway. "Would continue to warm for another, about another degree," he says.

That's enough to melt the Arctic — and if greenhouse gases continue to increase, the temperature will rise even more. The ice that's melting already is changing the weather by disrupting ocean currents.