DAVID POGUE: When it comes to building houses and roads, there are two different kinds of permafrost.

DAN WHITE: Gravelly materials.

DAVID POGUE: …the kind you can build on.

DAN WHITE: If you had a building, a road, on top of this, and you thaw that out, it would remain stable.

DAVID POGUE: The other kind of permafrost is the problem.

DAN WHITE: Fine grain soil.

DAVID POGUE: …which gets its structural integrity from frozen water that acts as cement.

DOUG GOERING: So long as it’s in the frozen state, you can see that it’s structurally sound. You can build roads or bridges or houses on something like this.

DAVID POGUE: Mm hmm.

DOUG GOERING: The problem, though, is that once it warms up, it turns into this.

DAVID POGUE: A scientific principle we call “melting..

DOUG GOERING: Exactly.

DAVID POGUE: And it’s only going to get worse as global temperatures rise. So how to stop it?

ED YARMAK: We use these thermosiphon devices.

DAVID POGUE: Thermosiphons. Ed Yarmak is chief engineer with the company that invented these things.

ED YARMAK: Well, it’s pretty simple; it’s just a tube.

DAVID POGUE: Here’s how it works: first, you put some liquid in. Next, you suck out all the air to create a vacuum. Then you get something cold.

ED YARMAK: I’ve got a little Fairbanks snow.

DAVID POGUE: Remember how things always move from hot to cold? Well, because the snow is colder than the air in the room…

Whoa! It’s going nuts!

…the cold draws the heat from the room into the tube, and.

It’s cool to the touch, it can’t be boiling.

Why is it doing that.

ED YARMAK: Your boiling point is dependent, not only on temperature, but on the pressure inside your tube or in your system.

DAVID POGUE: Because it’s in a vacuum, it boils at room temperature, moving the heat from the room into the snow.

Okay, got it. But how in the world is this going to save the permafrost.

Well, when you place one of these in permafrost, the heat from the permafrost moves into the thermosiphon.

One doesn’t think of permafrost as having heat.

ED YARMAK: Everything has heat, David. In the wintertime, the permafrost is warmer than the air above it. And we all know that heat goes from warm to cold.

DAVID POGUE: Okay, so the heat from the permafrost moves into the thermosiphon. The liquid inside boils, turning into a gas, which rises up, carrying the heat with it. When it gets to the surface, the heat moves out into the colder air.

So it stops thawing.

ED YARMAK: Exactly.

DAVID POGUE: And that works.

It’s true. In Fairbanks, you can see them around buildings, in roads, and along the 800 miles of the Alaskan pipeline, you’ll find 124,000 of them.