MADELEINE BRAND, host:
This is DAY TO DAY. I'm Madeleine Brand.
ALEX CHADWICK, host:
And I'm Alex Chadwick.
The U.N. today begins an international conference on global warming in Bali, Indonesia.
BRAND: We will visit a much chillier place now for the latest in our series with National Geographic on Climate Change.
Iceland is surrounded by the cold waters and blustery winds of the Atlantic Ocean right up at the Arctic Circle. You wouldn't think this would be a pleasant place to settle down.
CHADWICK: But more than 1,100 years ago swashbuckling Vikings from Scandinavia boarded their wooden ships and they packed on some livestock and some slaves to do the work, and they set out to settle the island.
Now researchers are coming to think that the story of the Vikings in Iceland was shaped by changes in climate.
Here's NPR's Richard Harris.
RICHARD HARRIS: It's easy to see how Iceland's history could be shaped by its climate once you experience the fickle weather here. When Unnsteinn Ingason steps out of the inn he runs in northern Iceland...
Mr. UNNSTEINN INGASON: (Unintelligible)
HARRIS: He first looks up at the sky to see whether it's sunny or snowing on this September afternoon. It could be both in this land of frequent rainbows. And when he gets behind the wheel of a four-wheel-drive SUV...
Mr. INGASON: (Unintelligible)
HARRIS: ...across the rolling grassy hills of the family farm, he is not just watching the road; he's also reading the landscape for telltale clues about Iceland's deep history, Viking history.
Mr. INGASON: (Unintelligible) you see more things. In the beginning I didn't see anything at all.
HARRIS: As we creep down a steep and rutted hillside, he says he can see the remains of a thousand-year-old farm boundary wall built by Vikings, or more likely by their Irish slaves.
Mr. INGASON: (Unintelligible)
Mr. INGASON: Look to your left.
HARRIS: We hop out of the truck, and he steps up onto a hump that runs parallel to the ridge.
This is an old wall you're standing on.
Mr. INGASON: Yeah.
Mr. INGASON: The local people has known of this for centuries, but nobody knows - knew what it was for.
HARRIS: Archaeologists eventually figured out that Vikings built a wall here out of piled up turf to coral their placid sheep and cows. That's not exactly the image we have of Vikings, who sailed their ships around Europe pillaging, murdering and otherwise terrifying the local populace.
But when Viking ships landed on Iceland sometime around 870 A.D., the island was essentially uninhabited. So they used their sharpened axes to cut down trees instead of doing battle.
Mr. INGASON: There will be just (unintelligible) not the Vikings like in the stories, robbing and killing everybody they saw.
HARRIS: Why would they settle down? We think of Vikings as going out there and making trouble.
Mr. INGASON: Yes. That that's a story.
(Soundbite of laughter)
HARRIS: One reason the Vikings may have settled down in Iceland was back then the climate was warmer and milder than it is today.
As Unnsteinn Ingason tells this story, a brisk wind whips up and a cloud blots up the sun. I reach for my jacket zipper, but he's happy in his fleece.
Mr. INGASON: You can always tell which are local people and which are tourists, because the tourists have more clothes on. You get used to it.
HARRIS: I wonder if the Vikings had a hard time dealing with changeable weather here also.
Mr. INGASON: Probably. And one theory is these huge boundary walls have been out of use between 1300 and 1400.
HARRIS: The boundary walls were abandoned during that century, probably because the climate changed; it turned cold. Animals died, farms failed, people starved. And here, it seems, there was nobody left to tend the boundary wall. So this hump on the ground hints at a much bigger story about just how much climate influenced the history of these early settlers.
Mr. INGASON: So it's like a giant puzzle which have been putting together very slowly.
HARRIS: Archaeologists are now on that case. They've been excavating Viking ruins up here in the farmland around Lake Myvatn for 100 years. And recently they've started to ask what these remains can tell them about how climate shaped the rise and fall of the Vikings.
Adolf Fridriksson runs the Icelandic Institute of Archaeology.
He stops his car on the road to let shepherds usher their flock of sheep down from their pastures, a tradition that dates back a thousand years.
Mr. ADOLF FRIDRIKSSON: (Icelandic Institute of Archaeology): When people came here first, I would think they found the place very inviting. It was covered with birch forests and people would have soon discovered the rich fishing grounds around to island, but also the trout and salmon rivers.
HARRIS: One of those salmon rivers flows through this gentle valley, past farmsteads that have been here for many centuries. Behind one of these farms we walk up to a long curving hollow at the foot of a hill, a Viking ruin.
Mr. FRIDRIKSSON: This farm was settled very early on, probably in the late 9th century. And people lived here, they for some reason they build this huge elongated with slightly curved (unintelligible). It's the biggest building from this period we know in Iceland.
HARRIS: People may have lived in it with their animals. Cows make pretty good radiators on cold winter nights. Or it might have been a temple to worship the Norse gods.
Mr. FRIDRIKSSON: (Unintelligible) now, but I think (unintelligible)
HARRIS: One thing's certain: the landscape soon changed. First, the farmers here chopped down all the birch trees to use as animal fodder and firewood. In fact, the Vikings deforested almost the entire island.
Also, volcanic eruptions spread ash and noxious chemicals across the land from time to time, poisoning the pastures. If that weren't enough, the temperature on this blustery Atlantic island rose and fell unpredictability. Livestock often couldn't survive that.
Mr. FRIDRIKSSON: When you're living at the edge of the inhabitable world, any small change may have a huge effect, especially if you are trying to live off nature, in isolation, as over here in Iceland.
HARRIS: Fridriksson says climate swings here were one reason Iceland's population didn't grow at all for nearly a thousand years,
Nowadays you can't find a Viking in Iceland. They inter-married with their Irish slaves and now walk the streets as native Icelanders.
You can even see hints of their tumultuous climate history in the culture of Iceland today.
Mr. FRIDRIKSSON: Some people complain that Icelanders, they never make any plans. Maybe that's because they have learned how to adapt to new and changing situations all the time. If you just look at the Icelandic weathers, there is this joke that if you're not happy with the weather, wait five minutes; it will change. And I am feeling bloody cold.
HARRIS: I am too.
Mr. FRIDRIKSSON: Okay.
HARRIS: So we stuff our hands in our pockets and head back toward shelter. Fridriksson says you might not notice it today, but the climate is once again getting warmer, and local farmers have told him that the birch trees are slowly but surely returning after centuries of absence.
Mr. FRIDRIKSSON: They said that they imagine that this land will become as it was when it was still untouched by humans in the Viking period.
HARRIS: So the environment here is changing yet again.
Richard Harris, NPR News.