Not far from the South Pole, more than half a mile below the ocean in a region that was once covered by ice, a layer of ancient fossils tells a surprising story about the coldest continent on Earth. Today, the South Pole records average winter temperatures of 78 degrees Fahrenheit below zero. But roughly 90 million years ago, the fossils suggest, Antarctica was as warm as Italy and covered by a green expanse of rainforest.

“That was an exciting time for Antarctica,” Johann P. Klages, a marine geologist who helped unearth the fossils, told Vox. “It was basically the last time the whole continent was covered by vegetation and probably also wildlife — dinosaurs, and all that.”

Intrepid polar scientists like Klages, who works at the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, are revealing new sides of the Antarctica we know today. In the April 2020 issue of the journal Nature, he and 39 colleagues described networks of fossilized tree roots that they pulled up from the seafloor in 2017. They’re a sign of just how much the polar climate has changed since the “supergreenhouse” of the Cretaceous period — and perhaps how much the climate could change again.

Even since that paper, the Antarctic surprises have kept coming. In October, a Brazilian research team announced that it found 75-million-year-old pieces of charcoal on James Ross Island, hundreds of miles south of South America. In the journal Polar Research, the researchers concluded that “paleofires,” which were common in the rest of the prehistoric world, also scorched the Antarctic Peninsula. “That’s exciting work,” Klages said. “It’s the first evidence for these wildfires.”

As climate change warms Antarctica and shrinks its enormous ice sheet, many scientists are wondering whether history could repeat itself. But relatively few research teams have the tools to work in a place where Titanic-sized icebergs pepper the ocean.

I sat down with Klages at the Falling Walls Science Summit in Berlin to talk about how his team conducted research from the RV Polarstern, a research icebreaker that translates “North Star” and regularly carries around 50 scientists and 50 crew members to the Arctic and Antarctic. He told me about the place where his team drilled into the seafloor — an area where geology somehow brought layers of 90-million-year-old sediment, or “strata,” within reach of their enormous and powerful drill.

The layers, he said, are like the pages in a book. “You walk along the pages; you walk along history,” he said. Our conversation has been edited and condensed.

Daniel Gross

Can you tell me a little bit about the 2017 voyage itself?

Johann Klages

All Antarctic expeditions I’ve been a part of are extremely exciting because everywhere you go, usually, it’s for the first time. It’s like this white spot on the map. Every time we go there we discover new things.

Polarstern is one of the largest research icebreakers in the world — it can break through thick ice. That makes it possible to reach locations that are usually not reachable for other ships. In the Northern Hemisphere summer, it’s usually in the Arctic, and in the Southern Hemisphere summer, it’s usually in the Antarctic.

This particular cruise was exciting because we tried this special seafloor drill rig for the first time. It’s huge. It’s almost 10 tons. It needs seven 20-foot containers of equipment to be shipped. There are only two of them available on the planet right now. They were developed and built in Bremen, Germany, at the Center for Marine Environmental Sciences (MARUM).

For this drill rig, you need special conditions. It sits on the seafloor and it’s connected with a long cable, in this case about 1,000 meters, for power supply and a glass fiber cable that ensures the communication. We have eight HD cameras that are observing each step. We the scientists are standing behind the technicians, because they are the specialists, in the communication container with all the screens that show you what’s going on.

Daniel Gross

It must look like a cockpit of an airplane.

Johann Klages

Yeah, or like in Houston when rockets go up. It’s very exciting. We know, when we drill, that no one has seen this material before.

It’s also extremely exciting because sea ice drifting toward the ship would be the end of the cable. Canceling the drill takes five to six hours. Therefore, we have a joint collaboration with the German aerospace center, and every day we get high-resolution imagery of the particular location where we drill. Then we have two helicopters on board. We fly around the ship to make sure there is no sea ice.

You need around 30 to 50 hours of operation time on one particular location. So for this time window, you have to make sure that everything runs relatively smoothly.

We had to drill through 25 meters 82 feet of sandstone, which is always the worst to drill, especially when there’s water involved, because it crumbles and falls apart. It’s really annoying. The drilling crew wanted to cancel the drill because of the sandstone and because ice was coming. We had to decide. I think the ice was eight or nine hours away.

Daniel Gross

Why did you drill there?

Johann Klages

Because during past expeditions, with geophysical methods looking deep into the seafloor, we saw that the geological strata were kind of tilted.

Daniel Gross

And that signals just how old it is.

Johann Klages

Exactly. If you have tilted strata, some kind of bigger tectonic process brought it up. Then the ice eroded into it, so that these strata are so close to the surface — just a few meters below the surface.

Daniel Gross

Is the drill sort of like a straw, in that it holds the sediment in place as it drills down?

Johann Klages

Yeah, you have an inner and outer barrel. At the bottom, you have a diamond drill head.

The seafloor drill rig has two magazines in it — one with empty barrels and one with filled barrels. You pull out the inner barrel every 3.5 meters. We then go and get the material from the technicians. That was the first moment we realized we have something very special because it had a color that we never saw before in Antarctica. Very dark brown, and very fine-grained.

At the surface, every once in a while, you could see these black spots. We were all wondering, what are these black spots about? Must be something organic.

We decided to drill one more section, which means 3.5 meters, and then go away. And in those 3.5 meters, there were those exciting strata. If we hadn’t, there would have been nothing exciting, really. That made the difference.

It’s always a combination of knowledge and good conditions, but then there are two more things: luck and intuition. If you don’t follow them, you shouldn’t go there in the first place.

We came home. The cores came home a couple of weeks later, shipped home on Polarstern. Then we decided to go to a hospital we have a collaboration with that has these human computed tomography (CT) scanners. When we first saw the CT data, that was the moment we realized we have something very special. It was this interconnected network of fossil roots.

Daniel Gross

Was there evidence of plant life in Antartica before you came along?

Johann Klages

Yes, but all of that evidence is 1,000 to 1,500 kilometers about 600 to 900 miles farther north. There was no evidence from near the South Pole. We reconstructed this environment only 900 kilometers away from the South Pole.

No one really knew what the climate was like during the “supergreenhouse” period near the South Pole. But this is actually what you need when you want to know the severity of a particular climate in Earth’s past. The poles are currently warming much more quickly than the rest of the planet, and as polar ice melts, global warming accelerates. This is what we could reveal with this study.

The problem in Antarctica is, right now, is the ice sheet. The particular site where we drilled was covered by grounded ice for millions of years, but since we are in an interglacial period right now, the ice retreated to a point that it just made it possible to get to it and drill into it.

Daniel Gross

Could you describe what was happening in the atmosphere at the time that could have created these conditions?

Johann Klages

That was the final question we asked ourselves. Such a diverse environment with such mild temperatures — temperatures that today you have in northern Italy, for example. What is necessary to maintain that for a long stretch of time 90 million years ago?

Therefore, we invited some climate modelers into our team. They came up with [a carbon dioxide concentration of] at least 1,100 parts per million CO2, which is four times preindustrial the CO2 concentration before the Industrial Revolution. This was needed, at least, to meet the conditions we reconstructed.

We knew this period was the warmest in the last 145 million years. Now we had much better numbers on the CO2 content.

The model still has a problem: It can’t really simulate well enough the gradient between lower latitudes and high latitudes. We now know that the gradient was very shallow.

Daniel Gross

So it’s likely that the climate was hotter but more even at the time.

Johann Klages

Yeah! This is something that models can’t do right now properly — to simulate this gradient. So there is a bug with the modeling.

This is now what brings it to the significance for the future of the climate, if we drift into a high-CO2 future. We are doing that right now. We are 420 parts per million CO2, something around that. If we go to this high-CO2 future, we know that models struggle. This is a chance to use moments in Earth’s past to calibrate those models, to improve their predictive capabilities for tomorrow.

Daniel Gross

And the predictions your colleagues are starting to make suggest that it’s very concerning — but the presence of the ice sheet itself could protect us?

Johann Klages

Yes. We are quite lucky now that we have ice, and that two big areas of our planet are covered by permanent ice mass: Greenland and Antarctica. You have this self-cooling process. You have a gigantic mirror that sends short-wave radiation that comes in, back into space. If this is gone, this is transformed into heat.

This is something that we should not take for granted. Ice is vanishing. Every year we go there, we see. We think “Oh my gosh — it’s really going quickly now.” The rapid changes going on are unprecedented, as far as we know so far from the geological past.

We are doing a big experiment right now. We take fossil fuels from the Earth’s crust that were deposited over millions of years, and usually would have been released back to the atmosphere over millions of years — but we did it within 150 years. Boom. That has never happened before. That has a massive impact.

This is something we need to incorporate when we talk about the future — to start learning what the planet already went through in its history. It’s the only chance we have. It’s not about environmental protection — it’s about human protection. It’s about us.

Daniel Gross

When you set out to become a marine geologist, did you ever think you’d end up researching something so pressing — the future of our climate?

Johann Klages

No. You drift into things. I was just fascinated by the planet and by its history. We are lucky to be part of it. But this particular discovery — if someone would have told me the story like three years ago, I would have laughed. I never thought it would have such an impact.

Correction, December 6, 11:30 am: Klages told Vox after publication that his team used eight HD cameras to monitor the drill rig on the RV Polarstern, not 20.