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IRA FLATOW, host:

You're listening to TALK OF THE NATION: SCIENCE FRIDAY. I'm Ira Flatow.

Up next, they look at what ancient DNA might tell us about the effects of global warming. You know, Greenland is covered with glaciers, which due to global warming are melting at a very high rate. And to turn back the clock and better understand the Greenland of thousands of years ago, scientists working there have taken ice cores from the southern part of the island.

Now, as you know ice cores are sort of a time capsule stretching into the past, because embedded in the layers of ice are samples of DNA, you have water, you have air, and all off taken together. They offer us a glimpse of what was the life like at that time, what was covering the land of Greenland thousands of years ago. And an analysis of the ice cores has led to some surprising discoveries about Greenland's past.

Joining me now to talk about the samples taken in Greenland and what they might tell us about what's happening on our planet today is my guest, Eske Willerslev. He is professor in evolutionary biology at the University of Copenhagen. He is the director of the Center for Ancient Genetics there and he joins us from Denmark. Thanks for taking the time to be with us tonight.

Dr. ESKE WILLERSLEV (Director, Center for Ancient Genetics): Yeah, thank you very much.

FLATOW: What was surprising about this ice cores from Greenland?

Dr. WILLERSEV: Well, first of all, the surprising discovery was when we went down to what is called the silty ice, it means basically the dirty part of the ice, the very close to the bedrock, and we try to obtain DNA from there. We've found, you can say, evidence of any ancient forests on Greenland, the conifer forest consisting of pine and spruce and taxus and alnus as well as some insects like butterflies and beetles and spiders. So that was, by itself, quite surprising because you don't find that kind of biological community on Greenland today.

FLATOW: How long ago was that?

Dr. WILLERSEV: Yeah, that was the next surprise. I mean, because most models that are, you can say, modeling the ice cap history of Greenland suggests that the southern part of the Greenland ice sheet melted away during the Eemian period for about 125,000 years ago where the temperature on Greenland was about five degrees higher than today.

But what our results suggested, I would say, is that that this ice had actually persisted there in southern Greenland for a longer period of time. So the forest community probably dates back to between 450,000 and 800,000 years A.D. And this is probably the vegetation for the last time that this area of Greenland was ice-free.

And this, you could say, as some implications also on our understanding on what ice caps and glaciers actually contributed to the enormous sea level rise that you saw during the Eemian period. You had a sea level rise of between, I think, three and five meters. And many people, I believe, that the southern part of the Greenland ice sheet actually contributed massively.

So it completely disappeared during this period of time. But because we found this very old ice, it could suggest that, although the southern part of the Greenland ice, it contributed for sure, it might not have contributed as much to the sea level rise as people previously would thought.

FLATOW: Hmm. How much…

Dr. WILLERSEV: However, with the emphasis, though, that this doesn't mean - you can say that in the future when we get temperature when we get temperature increasement that we will not see as sea level rise, it's just that we have to go back and find other sources for these, you can say, for the sea level rise than just the sort of Greenland ice cap.

FLATOW: Hmm. Couple of surprising results then.

Dr. WILLERSEV: Yup.

FLATOW: Yeah. I mean, to think that there was this forest and all that, all that wildlife there.

Dr. WILLERSEV: Yeah.

FLATOW: Consider what we see today.

Dr. WILLERSEV: Yeah, exactly. I mean, today, this area here's covered by two kilometers of ice. And the only very interesting thing about, I think the analysis was that it's actually quite surprisingly, you know, it's 10 percent of Earth's terrestrial surface today is covered with ice caps and glaciers.

And we have only very limited knowledge, you know, about what was the environment like in these areas prior to the last ice formation, and that because you can't really get access to fossils and all information because it's covered by these kilometer of thick ice. But - by the way, if you show that these ice cores that people drill in order to do climate analysis, climate studies, those can actually be used as well for reconstructing the environment.

So we could see that this forest community, for example, because it contains DNA from taxus, it probably did not have temperatures in the wintertime that was colder than minus 17.

And because you have spruce and pine, it probably didn't have temperatures in the summertime that was lower than about 10 degrees Celsius. So it also gives you some information about, you can say both the biology and the climate in the past.

FLATOW: Well, Dr. Willerslev, I want thank you for taking time to be with us. Good luck to you.

Dr. WILLERSEV: Okay, thanks.

FLATOW: Eske Willerslev is a professor in evolutionary biology section at the University of Copenhagen. He's also director of the Center for Ancient Genetics there.

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