ARI SHAPIRO, HOST:
One of the common arguments that American politicians use to question the threat of climate change is to say in various ways that the climate is always changing.
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PRESIDENT DONALD TRUMP: I think something's happening. Something's changing, and it'll change back again.
SHAPIRO: This is President Trump on CBS' "60 Minutes" in October just days after Hurricane Michael devastated the Florida Panhandle.
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TRUMP: I'm not denying climate change, but it could very well go back. You know, we're talking about over years and years.
LESLEY STAHL: Well, that's denying it.
TRUMP: They say that we had hurricanes that were far worse than what we just had with Michael.
SHAPIRO: And here's Senator Marco Rubio of Florida in 2016 at a Republican presidential debate.
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MARCO RUBIO: Sure, the climate is changing. And one of the reasons why the climate is changing is because the climate has always been changing. There has never been a time when the climate has not changed.
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SHAPIRO: Scientists find a lot wrong with this argument, and Stephanie Herring is here to tell us why. She's a climate scientist with the National Oceanic and Atmospheric Administration. Hi there.
STEPHANIE HERRING: Hello.
SHAPIRO: So is it true or not true that, as we just heard Rubio say, there has never been a time when the climate has not changed?
HERRING: So technically that's true. The climate has always been changing. But for various reasons, the current change that we're experiencing now is particularly alarming, and that is because in the history of human civilization, the climate has never changed this rapidly. And that's really what concerns scientists. It's not the fact that there is change, but it's the speed of that change.
SHAPIRO: Has there been a time when the climate was warmer than it is now?
HERRING: Yes, there has been. There's been several. Certainly when the planet was forming, it was incredibly hot here. But since there's been life on Earth - and one of the most notable in recent periods was about 56 million years ago. Temperatures were about 11 degrees Fahrenheit warmer than today plus or minus a couple degrees. Today's global average, for reference, runs around 60 degrees Fahrenheit over the course of a year. And then back then, it was probably closer to 70 or 73 degrees Fahrenheit.
SHAPIRO: And when the Earth was 11 degrees warmer than it is today, I imagine the continents looked very different than today. The places where cities are today might not have been places you would have built back then.
HERRING: That's correct.
SHAPIRO: So what makes this moment different? What has happened since industrialization that is a change from what we've seen over the last thousands of years of human existence?
HERRING: So if you were to walk back about 11,000 years, which is when most research tends to agree that human civilization began, global temperatures were actually really consistent. And that was great for human civilization. Most research thinks that because of the stability in our climate, it's allowed things like agriculture to thrive and our civilization to thrive.
And in fact, a study was done a couple of years ago that looked at temperature over the past 11,000 years, and it showed that temperatures climb for a few thousand years, and they kind of leveled off. And then it started to cool, and we had what's commonly known as the Little Ice Age where temps dropped. And that lasted about until the 17th century.
And then towards the end of the 17th century, we start to see them rise. And then we see the Industrial Revolution, and we see temperatures rise quite quickly. Global temperatures hit this cliff face in just 100 years, and we go from some of the coldest temperatures that human civilization has experienced to some of the hottest. And you actually need to go back around 125,000 years to find temperatures as high as they are today.
SHAPIRO: Well, what does that kind of change mean for human civilization?
HERRING: Yeah. So that's the second part of the question really - is, so what? Why should we worry about this? And the reason is really because our entire society is built around the climate that we know and that we've experienced. And the real question is, what kind of changes are we experiencing today that are going to impact the way we live our lives? The planet's still going to be here. The question is, what kind of lives do we want to be living while we're on it?
The other component of this is we actually know that changes in concentration in greenhouse gases are most likely due to human activity. Scientists actually have a way to look at the fingerprint of these different greenhouse gases, and so they can distinguish between greenhouse gases that have been burned through fossil fuel emissions versus just naturally occurring CO2 and other greenhouse gases in the atmosphere. And so we have a great deal of confidence that not only are we increasing greenhouse gas levels, but we're doing it because of human activity. And really then the question is, what kind of future do we want?
SHAPIRO: Stephanie Herring, climate scientist with the National Oceanic and Atmospheric Administration, thanks so much for joining us today.
HERRING: Thanks so much for having me, Ari. Transcript provided by NPR, Copyright NPR.