IRA FLATOW: This is Science Friday. I’m Ira Flatow. Yesterday, President Trump pulled the United States from the Paris Climate Agreement, leaving the list of other 194 countries that signed on in 2015 to reduce greenhouse emissions. Trump said the agreement imposed, quote, “draconian financial burdens,” unquote, on the US and that he would renegotiate the terms to make, quote, “a deal that is fair.”

Maggie Koerth-Baker’s here to fill us in on this historic decision. She’s Senior Science Reporter at FiveThirtyEight.com. She joins us from NPR Studios. Welcome back, Maggie.

MAGGIE KOERTH-BAKER: Hi. Thanks for having me.

IRA FLATOW: Let’s talk about this. First of all, President Trump held this press conference announcing the withdrawal. And his basis for pulling the US out of the agreement?

MAGGIE KOERTH-BAKER: Well, basically, his position is this was just a bad, bad deal. In his speech yesterday, he told the audience at the White House that the agreement was designed to hobble US economic success and transfer our money to other countries.

IRA FLATOW: And it’s interesting to note that in the agreement, the agreement says the withdrawal period is three or four years. So it would not take place while he would be in his first term.

MAGGIE KOERTH-BAKER: Well, there is one way that he could do that faster and that would be to withdraw from not just this agreement but from the 1992 UN treaty that the Paris Agreement is an outgrowth of. But that’s considered a lot less likely.

So yeah, it kind of comes down to this sort of interesting reality where President Obama signed us into this treaty as an executive order, which means that Trump can just turn around and take us out as an executive order. But with all of this being done by executive order, that just means that the next president can double undo what Trump already undid.

IRA FLATOW: Hmm. And there has been a response from some mayors and other officials around the country.

MAGGIE KOERTH-BAKER: Yeah. Cities and states are signaling that they might be willing to stay in the agreement, even if the federal government does pull out. So The New York Times was reporting today that there are 30 cities, three states, and more than 100 companies that are going to band together to submit a plan to the UN about the Paris Agreement.

And that’s really interesting politically. That’s something we’re watching at FiveThirtyEight because if cities start entering into global agreements on their own separate from the US government, that’s really weird.

IRA FLATOW: Yeah. Well, it’s free for them to do that, right? They can do whatever they’d like, free on their own?

MAGGIE KOERTH-BAKER: Yeah, for sure. It’s just definitely a different norm.

IRA FLATOW: Well, you could apply that to a lot of things going on in Washington, a different norm. That would be the title of your book.

You wrote a story this week that looked at when the environment became a bipartisan issue. I’ve always wondered what’s your take on this.

MAGGIE KOERTH-BAKER: So what was really interesting about this to me is that it sort of turns out that the fate of this agreement was kind of sealed all the way back in the early 1990s, which is when environmentalism really became highly partisan. So we were looking at several different lines of evidence. We were looking at how Republican Congress people voted and also at polling on the beliefs and opinions of conservatives and liberals and Republicans and Democrats.

And what we found is that there is this huge shift that you see starting around 1988 or so. And in just three to four years, you go very quickly from environmentalism being a fairly bipartisan idea to it being a complete nonstarter in conservative circles. Democrats got more entrenched around the same time period, too, but there’s this big split that happened and it wasn’t there before. And it happened quick.

IRA FLATOW: See, I always thought it had something to do with Al Gore’s book and his participation in it.

MAGGIE KOERTH-BAKER: Well, what the researchers spoke with– Aaron McCright at the University of Michigan, he thinks that it actually has a lot to do with the Cold War. So he’s working on this paper where he went back and read every issue of several conservative magazines between 1970 and 2014. And he saw the rhetoric shifting a lot in the late ’80s, too.

So you went with environmentalism sort of being this replacement for communism, actually, that there was this new threat to the free market and you started seeing even these slurs tossed around, like people being called “watermelons,” green on the outside, but inside, it’s red.

IRA FLATOW: Wow. Wow. Let’s move on from this because we could be here all day long.

Let’s go on to CRISPR. CRISPR’s an exciting topic. There are a couple of CRISPR trials happening in humans.

MAGGIE KOERTH-BAKER: Yeah. So this week has been good news, bad news for CRISPR. On Tuesday, New Scientist reported that there are at least 20 new human trials that are kind of getting off the ground, most of them in China– a couple also in the UK. There’s one that’s supposed to be starting in the US sometime next year.

And these include a trial of a technique to fight cancer-causing HPV virus, where researchers will actually take a gel containing that CRISPR machinery and put it directly on women’s cervixes. So it’ll kill the virus in infected cells but leave the healthy cells alone. And this was really cool, but then later in the week, you got this other bit of news that there’s a new study where researchers found that the algorithms that they’ve been using to predict unwanted side effects of CRISPR maybe don’t work as well as we thought they did.

IRA FLATOW: What do you mean by that?

MAGGIE KOERTH-BAKER: Well, so CRISPR causes mutations, effectively, right? And they’re mutations that we want and we know that there’s this risk of it causing some mutations we don’t want. So what people have been doing is using these algorithms to sort of predict the amount of mutations based on what genes you’re targeting and how you’re using the tool.

But it turns out that this works better in a test tube than it does in an actual living body. So they did the study of a CRISPR fix for blindness in mice and they successfully altered the gene that was causing blindness. The mice could see. But they also found that it caused more than 1,500 unintended mutations that weren’t predicted by the algorithm.

The mice didn’t experience these high rates across the board. There were two mice that were particularly affected in ways that others weren’t. But it’s really hard to guess what impacts these gene mutations would have and cancer’s always the big risk.

IRA FLATOW: Yeah. CRISPR’s not a very precise way yet.

We’ve been talking here about the solar eclipse. We’re all looking forward to that in August. There will be a lot of sun science happening. But NASA is sending a probe– first probe that goes right into the Sun?

MAGGIE KOERTH-BAKER: Well, not right into the Sun.

IRA FLATOW: Close enough?

MAGGIE KOERTH-BAKER: It’s pretty close. Four million miles– is that close enough for you?

IRA FLATOW: I think so. It’s a little toasty at that point.

MAGGIE KOERTH-BAKER: It’s definitely a little toasty. And what it’s actually studying is the corona, which is kind of like the Sun’s atmosphere. And the corona is actually hotter than the sun itself– so 1.8 million degrees Fahrenheit, which is really hot. So the probe is going to be at least four million miles away from that in an area where it’s only 2,500 degrees Fahrenheit. And it’s expected that its mission will last until 2025 and then it’ll just stay in orbit around the Sun after that.

IRA FLATOW: Hmm. Collecting data– has it got all kinds of heat-resistant material built around it?

MAGGIE KOERTH-BAKER: It does, yeah, carbon composite materials. And one of the reasons that we’re only doing this now is because these materials just became available. And before that we couldn’t have done this kind of study.

IRA FLATOW: Hmm. Well, visiting the corona– I’ll drink to that, Maggie. Thank you.

MAGGIE KOERTH-BAKER: Absolutely.

IRA FLATOW: Thank you for taking time with us today. Maggie Koerth-Baker is senior science editor or science reporter, senior reporter– all those things– at FiveThirtyEight.com.

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