IRA FLATOW: This is Science Friday. I’m Ira Flatow. Our current era of climate change is unprecedented in human history. But it’s not the first time the Earth has been through such a change.

56 million years ago, shortly after the extinction of the dinosaurs, the planet warmed faster than it has at any other point in time except for today. Can something be learned from history repeating itself? Here to discuss that question and other short subjects in science is Sarah Kaplan, science reporter for The Washington Post. Welcome back.

SARAH KAPLAN: Thanks.

IRA FLATOW: Good to see you in person.

SARAH KAPLAN: Yeah. Good to see you too.

IRA FLATOW: All right. Let’s talk about this. So what happened 56 million years ago? Why was it getting warmer?

SARAH KAPLAN: Yeah. So it’s this period called the Paleocene-Eocene Thermal Maximum, which–

IRA FLATOW: Whoa!

SARAH KAPLAN: –if you don’t run out of oxygen just getting the name out, it’s actually a really critical period in Earth’s history. Over the course of about 5,000 years, huge amounts of carbon were released into the atmosphere, something between 4 and 7 trillion tons. And 5,000 years doesn’t sound like a lot– it doesn’t sound very short, but it’s really fast, geologically speaking.

And we know what happens when carbon goes into the atmosphere. The Earth heats up. So we think that the Earth heated about 5 to 8 degrees Celsius. And if you think about that in today’s terms, we’re talking about trying to limit Earth’s– the rise in temperature to 2 degrees. So that was quite a lot at the time.

IRA FLATOW: So you had ocean warming and acidification and weird weather and all the stuff that went along–

SARAH KAPLAN: Yeah so–

IRA FLATOW: –with that.

SARAH KAPLAN: I mean, some of the things we’re seeing now, those same things happened during the PETM. There were mass extinctions. Mammals actually got smaller. That’s something we haven’t see yet.

IRA FLATOW: They got smaller?

SARAH KAPLAN: Yeah. The ancestors of modern day horses, which, at the time, had been roughly the size of dogs, they shrunk down to the size of house cats–

IRA FLATOW: Wow.

SARAH KAPLAN: About 30%. And then, also, like, things started showing up in places where they shouldn’t be. So the main place to look at the PETM is in the Big Horn Basin in Wyoming. It’s kind of like a Badlands area. But right before the PETM, it was kind of like Florida. It was sort of a swampy, warm place, and very wet.

And then during the PETM it got super dry, and the kinds of plants that you see there change. And also, they have a lot more insect bites in them, which is weird.

IRA FLATOW: So is this what we have to look forward to?

SARAH KAPLAN: Well– [LAUGHS] You know, the hope is that we’ll learn from the past, right? We know what the consequences are. And climatologists, who are trying to predict, you know, what will happen as we continue to add carbon to the atmosphere today, maybe knowing what some of the consequences are, including the fact that it’s going to take 150,000 years to get back to normal. That’s how long the PETM took to recover. So maybe we can learn from Earth’s past.

IRA FLATOW: Oh, we hope– we hope so.

SARAH KAPLAN: Yeah. Yeah.

IRA FLATOW: All right. Let’s move on to something different. Scientists have uncovered the fossilized footprints of ancient Americans doing something. What were they doing? What was happening there?

SARAH KAPLAN: Yeah. So on this island off the coast of British Columbia, they’ve actually uncovered 29 prints from people living 13,000 years ago. And it kind of looks like they were climbing out of a boat. There’s sort of– there’s three different sets of prints representing three different sizes. So they look kind of like two adults and a child. And they’re all kind of trampling over each other. And so it kind of looks like they were getting out of a boat and coming on to land.

IRA FLATOW: Wow. It’s amazing they could be preserved.

SARAH KAPLAN: Yeah.

IRA FLATOW: Especially in that kind of watery situation, where you might have– you know, if we were walking on the sand, it would be gone.

SARAH KAPLAN: Yeah. So you have to get very lucky. I mean, there’s not that many fossil footprints in the world. And sort of just the right circumstances have to collide. But these prints are really important because scientists have been questioning for a while, how did people get down into the Americas once they crossed the Bering Land Bridge at the end of the Ice Age?

And they couldn’t cross through the middle of Canada because it’s covered in a gigantic ice sheet. So one thought is that they took boats down what’s called the Kelp Highway. And this is sort of suggestive of that.

But it’s also really important to the native community that lives there, the Heiltsuk First Nation. They have an oral history that says that their people arrived in this area at a time when the continent was covered in ice. And I spoke with a representative from the community who said, now we can see, this is a place where ancestors walked. And here we still are today.

IRA FLATOW: Wow. What a great story. We also received news this week that the launch of the James Webb Space Telescope is going to be pushed back yet again. This time, to 2020, right?

SARAH KAPLAN: Poor James Webb just can’t get off the ground. This telescope is conceived as kind of the bigger and even more impressive successor to Hubble. It’s supposed to be able to look back to Cosmic dawn, when the first stars emerged. And it was originally conceived in 1996 and was supposed to launch sort of in the mid-2000s, if you can believe it.

It is now 2018, and it’s still in what’s known as the integration and testing phase. It’s been delayed so many times. And now, more problems have popped up. So this week, NASA said they’re going to push back the launch at least a year, from– it was supposed to launch next spring, and now it’ll be May 2020 at the earliest.

IRA FLATOW: I mean, they’ve spent $8 billion on it so far. Are they’re going to go over budget even more than that?

SARAH KAPLAN: Yeah.

IRA FLATOW: Congress will give them more money to do this?

SARAH KAPLAN: Well, we hope so. Or, I guess, astronomers hope so. Congress had passed a $8 billion funding cap on the telescope, and they’re probably going to exceed that. So now NASA’s going to have to go and ask for re-authorization.

IRA FLATOW: You know, the thing is I remember when the Hubble Space Telescope went up. I remember, we interviewed the crew that, you know, went up and fixed it. The kind of stuff like that. They could actually go up and replace parts. They can’t do that? Send it up a little bit broken?

SARAH KAPLAN: No.

IRA FLATOW: Then fix it?

SARAH KAPLAN: James Webb is going to go out four times farther than the moon, about a million miles from Earth, which is further than any human has ever been, and way too far to be fixed in orbit. So NASA kind of– I mean, that’s what the folks at NASA say, is that they need to make sure that the telescope is perfect when it launches, because if it goes into orbit, that’s it. That’s what we’ve got.

IRA FLATOW: That’s it. You’re stuck with the– you have to go into orbit with the satellite you have, not the one–

SARAH KAPLAN: Yeah.

IRA FLATOW: All right. Well, something that is in space but won’t be there for much longer is this Chinese space station that is tumbling out of orbit. It’s going to come crashing down.

SARAH KAPLAN: Yeah. It’s Tiangong-1. It was launched in 2011, and China lost contact with it in 2016. So we’ve sort of known for a while it was going to– its orbit would decay and eventually would crash down to Earth. And now it’s finally going to happen this weekend, probably sometime between midday Saturday and midday Sunday.

And the chance of anyone getting bonked is pretty unlikely. I think it’s been estimated to less than 1 in 1 trillion. But if you find a piece, don’t touch it because there’s hazardous hydrazine fuel, probably, on the pieces. And also, they’re technically still the property of the Chinese government, and they may want it back.

IRA FLATOW: You have to pay tariffs on it also.

SARAH KAPLAN: Yeah.

IRA FLATOW: In this new environment. Thank you very much, Sarah.

SARAH KAPLAN: Yeah.

IRA FLATOW: Sarah Kaplan, science reporter for The Washington Post.

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