These rocks are just chunky silt stones that are quite near the petrified forest. KIRK JOHNSON: Oh, there’s a 30,000-year-old piece of ground squirrel poo. …an Arctic that was once a warm, humid swamp; Antarctica, full of dinosaurs; and a time when ice sheets extended from pole to pole, turning Earth into a giant snowball. Since all plants use carbon dioxide to grow, a plant that’s been around that long might be able to tell us how CO2 levels have changed. Black Hole Apocalypse. This is great. This is an extraordinary piece of evidence that demands extraordinary (not simple) conclusions, such as is often said in popular media: just reduce human-generated atmospheric carbon and we'll be OK. To his credit, the host-Kirk Johnson, who holds a doctorate in geology and paleobotany from Yale University-takes the opportunity to assert: "Today we live on a planet that has ice at both poles, and we think that's normal because that's our world-but when we look at the fossil record we realize that it has had only four episodes where there's been glacial ice-only about 25% of the last 500 million years has our planet been like it is today. JEREMY SHAKUN: Oh, wow. If we go deeper into the cave system, we can see what happened when it warmed in the past. And what Rich is discovering is that adding extra CO2 does something striking to the stomata. Nowhere is that more dramatic than at the mighty Jakobshavn glacier in Greenland. I lived here when I was eight years old, until I went to college. So, it’s a good idea, but the science says nope, there really were polar warm forests. Now we have to ask ourselves: is this the world we want? Each year, the sea ice at the poles melts and refreezes with the seasons, growing in the winter and shrinking in the summer. So, let me show you this. Last year it froze in January. Back then, though there was ice at the South Pole, the north was mostly ice-free. When this gingko was alive, 56-million years ago, about the same time that swampy forests were growing on Ellesmere Island in the Arctic, the amount of CO2 in the air was roughly four times what it is today. Water ran off the land, forming a surface layer of freshwater. KIRK JOHNSON: It’s like a gigantic igloo. Just like a little scoop? The rock and soil beneath the surface are permanently frozen all through the summer. (60 minutes) Can't find the episode you're looking for? KIRK JOHNSON: So, this goes around this side. This material is based upon work supported by the National Science Foundation under Grant No. It’s almost unimaginable to think that I can paddle a kayak around in a landscape of floating frozen ice. KIRK JOHNSON: The helicopter hovers just above the surface. And once it was there, ice sheets could spread quickly, sometimes, even reaching Seattle, my hometown. It hasn’t rained in a while. The crops we depend on for food will be vulnerable to the extreme hothouse weather. It’s the final stage of a process that’s been driving our climate for millions of years: the carbon cycle. JAELYN EBERLE: Ah, probably not, but could be a little piece of bone. KIRK JOHNSON: Lots of little crevasses here. And almost everything you pick up is undiscovered. So, it sort of keeps the refrigerator door closed on this mighty icy continent, because the current was then allowed to go right around the continent, endlessly around, endlessly around, keeping it cold and frozen. CLIFFORD WEYIOUANNA: Well, all these years, you know, the sea ice was dependable. The question is, are we clever enough and forward-thinking enough to flip that switch back? You could think of them like a frozen lasagna you’ve put in a pre-heated oven, you know? This is a huge rock. So, you want to use this little tiny mud pot? I love it here. There’s an evolutionary advantage: smaller bodies lose heat more quickly. During the hunting season, he flies his drone to help the villagers find the safest path across the sea ice. But it hasn’t always been this way. And that depended on a stable climate. This little coastal town in Alaska is only 30 miles south of the Arctic Circle. DAVID HOLLAND: Is it possible to go slightly lower? It just goes around and around in the sky. KIRK JOHNSON: Geologist Kayla Iacovino studies volcanoes all over the world. KIRK JOHNSON: With South America and Antarctica connected into one continuous continent, these munching monsters had plenty of forest to roam in search of a good meal. We’ll just dump it on this side. KAYLA IACOVINO: Do you want hold on to this? But what kind of trees were these? KIRK JOHNSON: …to unlock the hidden history…. It’s big, but it’s nothing compared to the biggest dinosaurs. KIRK JOHNSON: …and then go destroy another forest. Are you all ready to go? 1713552. KIRK JOHNSON: So, we’re sitting here in Death Valley, and it’s about 95 degrees, and you’re pointing to a rock and saying that it was deposited by a giant slab of glacial ice? Around 56-million years ago, this stretch of Wyoming was a warm lush floodplain, covered in a subtropical forest of laurels, legumes and palms, a bit like northern Florida today. There is no rain and there are no rivers. Look at that. And what does it mean for our planet’s future? JULIE BRIGHAM-GRETTE: This isn’t found anywhere earlier in the lake history. This is the greenhouse effect, which drove Venus to get hotter and hotter. The weathering part of the carbon cycle is stalled. KIRK JOHNSON: Yeah. Watch Preview. We had waves in January. Paleontologist Kirk Johnson explores the polar extremes of the planet, including miles-high ice sheets and warm polar forests brimming with life. Cold knees. As has been done elsewhere, this NOVA episode presents the irresistible comparison of the runaway greenhouse on the planet Venus and its components (e.g., carbon as the greenhouse accomplice) against reported current era carbon increases on Earth to draw towards a conclusion that we're on track to a similar state of affairs, though (clearly) Earth need not resemble Venus closely to become barren and lifeless. KIRK JOHNSON: Jaelyn’s spent many summers up here searching for fossils. JEREMY SHAKUN: It’s just old dead stuff. (Kirk Johnson, Sant Director of the Smithsonian Institution’s National Museum of Natural History, stands at the edge of an ice sheet in Greenland). And the pools are literally boiling beneath our feet, because right under these mountains is one of the largest super-volcanoes in America. Net-net, this episode comes out on the plus side of that criterion. We don’t think anything about them. We’ll see if there’s any water in it. Piecing together data from sites across the globe, scientists can build a temperature timeline going all the way back to 500-million years ago. We’ll zoom in. How old is this one? of Culture and Heritage Location, NYU Abu Dhabi Center for Sea Level Change (CSLC), Vulcan Lands Inc and Vulcan Construction Materials, LLC, Jason Amundson/University of Alaska Southeast, A NOVA Production by Windfall Films (part of the Argonon Group) for WGBH Boston. Now they use giant water jets that make a firehose seem like a garden sprinkler. Following a trail of fossils found in all the wrong places–beech trees in Antarctica, redwoods and hippo-like mammals in the Arctic–NOVA uncovers the bizarre history of the poles, from miles-thick ice sheets to warm polar forests teeming with life. KIRK JOHNSON: There’s almost no ice at all. The ice eventually started to retreat, leaving an ice-free corridor that allowed ice age animals, and later people, to migrate between Asia and North America. Following a trail of fossils found in all the wrong places–beech trees in Antarctica, redwoods and hippo-like mammals in the Arctic–NOVA uncovers the bizarre history of the poles, from miles-thick ice sheets to warm polar forests teeming with life. KIRK JOHNSON: I’m not leaving. GRANT ZAZULA: That’s 25- or 30-thousand year old ice in there. ALEXANDRA ROTHERMEL (United States Department of the Interior, Death Valley National Park Ranger): So this is our rain gauge. What’s falling on my hands and my face right now is rain in the mountains, and it’s got dissolved CO2 in it. Polar Extremes. KIRK JOHNSON: Shishmaref is just one example. In fact, we can use the chemistry of rocks and fossils to find the temperature at the time those rocks formed. You see, here’s, get a close up of that thing. KIRK JOHNSON: We’re trying to reach a layer of mud that dates back 3,000,000 years. For me, this is a pretty mind-blowing realization. BRIAN ROUGEUX: Malick, if you’re able to drop me and then take off for a bit, that, that makes it quite a bit easier for me. To find what Maureen’s looking for, we need to dig deeper, and my rock hammer just isn’t going to cut it. DENNIS DAVIS: …where the ocean is open, when it’s supposed to be frozen. Let’s call that fire “sun” and here’s…I’ve got a little bit of a globe right here. Many scientists say we’ve entered a new geologic age: the “Anthropocene,” with humans now altering Earth’s climate on a geological scale. That’s what we call an Arctic landing right there. Then the permafrost kept on melting. How much warmer was it 400,000 years ago? That takes us way out of whatever boundaries existed over the last 800,000 years. This is telling me that this landscape is covered by expansive grasslands. Even minor variations in temperature cause very rapid evolutionary change. KIRK JOHNSON: The team takes readings from 12 different positions along the length of the fjord. The one that sank the Titanic probably came from here. Etna, in Italy, is built on carbon-rich rocks and belches out more CO2 than almost any other volcano. And layer by layer they build this thing up. We can find clues from a close neighbor in our solar system. What caused such dramatic changes at the ends of the Earth? JON BLOCH: You can see this very strong red bed that’s really consistent…. KIRK JOHNSON: What these rocks tell us is that 640-million years ago, the climate here in Death Valley must have been much colder, so cold that what’s now a scorching desert was covered in giant sheets of ice, as big as you’d find in the polar regions today. Later in the summer, David and Denise witnessed one of the biggest calving events ever captured on camera. This is a control tree at 400 parts per million; 600, the next treatment up; 800 parts per million; and the final tree is a thousand parts per million. Over thousands of years, these layers build up until they form an ice sheet. My first stop on this journey is one of the most remote places on Earth, with some surprising secrets locked in its rocks. I’m joining Denise and David Holland and their team of scientists from New York University. KIRK JOHNSON: And there’s no, there’s no Arctic grasslands today at all? That is pretty weird. Hey, first carnivore. Some of these are dripping just a little bit. After hundreds of generations of humans have settled across this icehouse world, the planet’s temperature is rising and the polar regions are changing. Polar Extremes . DAVID HOLLAND: So, we’re going to deploy carefully. KIRK JOHNSON: Searching for animal fossils in the permafrost is really tough. I mean, this leaf and that leaf are almost identical. NOVA: Polar Extremes Join renowned paleontologist Kirk Johnson on an epic adventure through time at the polar extremes of our planet. We are doing a circle around the position. Following a trail of fossils found in all the wrong places–beech trees in Antarctica, redwoods and hippo-like mammals in the Arctic–NOVA uncovers the bizarre history of the poles, from miles-thick ice sheets to warm polar forests teeming with life. Further, with oceans begining to turn to water vapor there would be increasingly no "sink" for the emissions from volcanoes other than the atmosphere, so the greenhouse effect would gain momentum in such conditions. I think everything that could be found has been found. This is incredible man. Episode Clips. Once camp is set up, Jason is going to help me find a special site that I never got to see the last time I was here. This time, they need to drop probes into the water just in front of the calving edge. Nova: Polar Extremes Following a trail of fossils found in all the wrong places–beech trees in Antarctica, redwoods and hippo-like mammals in the Arctic–NOVA uncovers the bizarre history of the poles, from miles-thick ice sheets to warm polar forests teeming with life. At a remote site in Argentina, a team of paleontologists has just discovered the remains of a forest dweller that must have had a very large appetite. KIRK JOHNSON: The level of carbon dioxide in the air is around 410 parts per million, but the reading from the mud pot is much higher. It’s right before we slid into the ice ages. KIRK JOHNSON: Today, Earth’s volcanoes are relatively quiet and aren’t cooking up a whole lot of CO2, but in the past it’s been a very different story. MARCELO LEPPE (Director, Chilean Antarctic Institute): After a week, we didn’t find a fossil. It just looks like Mars, it’s a magical place. JULIE BRIGHAM-GRETTE: Yeah. Here, in Antarctica, this mountain terrain is encased in ice year round. And some species grew to be the biggest animals that ever walked on land. I’m looking at Venus. KIRK JOHNSON: These are the earliest horses to evolve on Earth, 56-million years ago, and they lived right here in Wyoming. We know that at certain points throughout Earth’s long history, volcanoes and other geologic activity released much more CO2 into the atmosphere than today. This leaf is from southern South America, and it’s very characteristic of the beech family, as is this leaf from Antarctica, that we just collected this morning. JASON HILLIER: Yeah, it’s definitely something we have to be careful of with this mud. Even in summer, the temperatures rarely ever get above freezing. The amount of CO2 that we’ve added to the atmosphere, that’s now raised us up to 400 parts per million. To understand how, you need to get the big picture, and luckily, I know a place with a spectacular view, a spot I dreamed of climbing when I was a kid….

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