You mean cap-and-trade?
Two-thousand pages of giveaways to everybody. That year I went to John Kerry’s office, and had a long discussion with him. And in principle he seemed persuaded a carbon fee made more sense than cap-and-trade, but he said, I can’t get one vote for it. In order to get a senator or representative to vote for it, you have to give them something, for their district.

It’s interesting, there’s this whole little school in political science which argues the ending of earmarks was actually disastrous for the working of American politics, because now we don’t even have that to bargain with any more. And so the only thing politicians can strategize about is how close they are to party leadership. Obviously partisan cooperation was declining well before that, but the end of earmarks have made compromise even harder.
That’s interesting.

In your view, why is a fee so much more effective than a cap-and-trade system?
What’s the cap on India? You have to have a system that can go international. You only need, frankly, the U.S. to have a carbon fee, and then you have border duties on products from countries that don’t have a carbon fee, and that’s incentive for other countries to have their own carbon fee. When you try to cap something — unless it’s across the board, on everything, it just reduces the demand. A successful cap that reduces the demand makes it cheaper. And how would you put a cap across coal, oil, and gas? That’s not the way it works. And also the public is simply not going to let it happen. They see the price at the pump going up, and they’re not going to get the money … It doesn’t even have to go up very far.

You know, over the weekend, I was trying to finish this paper — it’s called “Young People’s Burden.”

Yeah, you sent it to me.
I think it’s about to be accepted. People have been so reluctant to accept these papers.

Why do you think that is?
Because — it’s what I call ‘scientific reticence.’ I wrote a paper in 2007 called ‘Scientific Reticence and Sea Level Rise.’ You’re rewarded in science for not stepping out too rapidly.

But I was working on a video over the weekend with my oldest grandchild, to try to get people to understand this. The narrative that is out there is completely wrong. The narrative is, Al Gore says we’ve turned a corner. It’s actually getting worse! The annual addition is increasing — it’s not only that we’re not going down, we’re increasing the forcing.

One of the few areas where encouraging news is coming from is green energy — that seems to be coming a bit faster than most people expected, and more cheaply than most people expected.
But it also seems like the news we’re receiving from the Arctic in particular is just much worse. You also think carbon removal is important, right?
At the time of our 2013 paper, for the first lawsuit, we argued that you could get carbon down to 350 parts per million by the end of the century without technological extraction. But now, in our new paper — which I hope will be accepted this week — we are saying until 2020 emissions are going to be more or less similar than they are now. To start reduction at that time, in order to get back to 350 ppm by the end of the century, we’ll have extract 50 gigatons of carbon technologically, in addition to 100 gigatons we’d need to extract in these quasi-natural agricultural and forestry ways. Fifty gigatons is a lot. The cost of that is in the trillions of dollars.

And I know a lot of scientists are really worried about how to do that. It doesn’t seem like a consensus that we know how to do it even if we had the will and the money.
And it is going to cost to money, because it takes energy. So I just don’t think that’s very plausible.

When I read the IPCC stuff, but also other academic papers, it seems like that two-degree threshold is really quite optimistic, and that we’re on track for something more like four or five degrees. You’ve mostly focused on the danger of that optimistic outcome — 1.5 to 2 degrees. I’m curious why you’ve focused on that level, that end of the spectrum, and also what worries you have about things getting somewhat significantly worse than that.
What I focused on is, what is the carbon that you should aim for, if you want to avoid some strong feedbacks and large consequences. In 2006 I think it was … Bill McKibben asked me what should be the target for CO2. He was going to form this organization,, and that’s when I told him, hold on, what I’m finding is that’s actually a pretty dangerous level. So he did hold on for a while. So what should humanity aim for? It’s not any larger than 350 ppm, and it might be less. It just turns out that if you look at the paleoclimate, it’s really very sensitive.

I just think about all those greenhouse extinctions, and how dramatically those changes unfolded.
The natural climate changes move much slower. The one that looks like a spike, like a delta function, the biggest one, is the PETM — and that took a couple thousand years. We’re talking about a couple of centuries.

The rapidity with which we’re going through it makes it all that much harder for ecosystems to adapt, and species to adapt.

To think for a minute at the scarier end of the spectrum. If we do end up four or five degrees warmer, within a relatively short period of time — that’s the IPCC’s RCP8.5 scenario, by the end of the century, and that’s not counting some of these dramatic feedback mechanisms, what would that do to the planet, in your mind?
I don’t think we’re going to get four or five degrees this century, because we get a cooling effect from the melting ice. But the biggest effect will be that melting ice. In my opinion that’s the big thing — sea-level rise. Because we have such a large fraction of people on coastlines — more than half of the large cities in the world are on coastlines. The economic implications of that, and the migrations and the social effects of migrations — the planet could become practically ungovernable, it seems to me. But if you’re really talking about four or five degrees, that means the tropics and the subtropics are going to be practically uninhabitable. It’s already becoming uncomfortable in the summers, in the subtropics — you can’t work outdoors. And agriculture — more than half of the jobs are outdoors.

Food production seems a real worry.
Population is a problem. That’s why you want to have energy that’s needed for people to eliminate poverty, because countries that have become wealthy have the population under control. But if you do begin to lose major cities than the planet becomes ungovernable.

And what level of sea-level rise would precipitate that? What worries you?
Once sea levels go up significantly, you won’t have stable shorelines. Just parts of the city will go under water, but then it doesn’t make sense to continue to build there. So, I don’t know. By the time you get to even one-meter rise, you’re going to be losing more land. We argue in our paper “Ice Melt, Sea Level Rise, and Superstorms,” which we published in 2016, that you could get multi-meter sea-level rise in 50 to 150 years.

To switch subjects for a moment, can you tell me about the end of your time at NASA?
It became— I was getting involved in more and more of these outside activities. I mean, suing the government is not something you can do on government time! And getting arrested five different times — NASA was not very happy about this. Plus, I needed more time for my other work.

When was that?
Early 2013.

And how do you think the new administration changes things?Now we have an easy target, because what they’re doing is so crazy. I don’t see how we can lose. Because what they’re doing is so dangerous. Obama —he was continuing to approve offshore drilling and the things which, we would argue, don’t make sense, since we have to phase out fossil fuels. But now, it’s just so extreme, I think that makes it a much easier case. They’re willingly doing things that are certain to cause great harm to young people and future generations.

It seems almost out of spite. The Obama record is obviously mixed on these issues, but you at least got the sense there was some intellectual sympathy, even if they were compromised in what they were able to do. But the motivations of this entire administration just seem so … nasty.
But they’re consistent with what the fossil-fuel industry wants, and they’re providing a lot of funding to Republicans especially.

Although some of the reporting I’ve seen is that the people in the fossil-fuel industry have been shocked at how much they’re getting from the new administration.

Like they were asking for a hundred bucks and getting a thousand and going, “Okay, we’ll take it!” What do you think is going to happen to Paris?
I doubt that Paris withdrawal makes much difference. Countries that only promised to do what they felt was in their best interest anyhow, so I don’t think countries will back off. And I think this will be a short-lived reversal by the U.S., whether it’s from the courts or the next election.

And are you encouraged by the news out of India and China?
Yeah, although it’s misstated by the environmental community as if they’re solving the problem. They’re not closing their coal plants, and as I mentioned globally the rate of greenhouse-gas growth is actually accelerating. So you do have to have some carbon-free alternative energies to complement the renewables. I don’t know of any alternatives — you have hydropower, for a certain amount, in certain countries, but I think we should have been working with China to develop safe nuclear power. That’s the only way that they will get rapidly off of coal. That has been a mistake. We should have put a price on carbon rather than trying to have regulations that choose specific technologies.

Do you think people are too scared about the risks of nuclear power?
I think there’s a lot of misinformation. It’s incredible. More than 10,000 people are dying each day from the small particles coming out from fossil-fuel burning, which is more than have been killed in history from the radiation from nuclear-power plants. It’s an irrational fear of low-level radiation. You have to avoid high levels of radiation, but we know ways to do nuclear which are much safer — that will not explode, that won’t produce a meltdown. But the real thing that’s needed is a simple, honest carbon price.

I know you started your career working on Venus, and some of the fringier people I’ve talked to point to Venus as a scary allegory for how climate change can really transform a planet.
Well, yeah, but it took a very long time. One flaw in my book Storms of My Grandchildren is my inference you can get runaway climate change on a relatively short timescale. You have to get rid of the ocean before you get to a Venus situation, and that requires you getting the water to escape. That took hundreds of millions of years for that to occur on Venus. You could certainly get to a disastrous situation without getting rid of the ocean, but if you want to go to a Venus-type situation, then you have to lose the ocean. Venus did. Hydrogen isotopes on Venus do indicate that it once had a lot of water, but doesn’t now.

Do you think that’s possible on a many-millions-of-years timescale?
It can’t be done with fossil-fuel burning. It can and will be done as the sun becomes a red giant. But that’s going to be billions of years.

Is there anything you’d say about the shorter-term disaster scenario?
I think on the shorter term, the planet becomes much less habitable — low latitudes become less habitable, and if we lose coastal cities everything starts going backwards. The progress we’ve had over the last centuries, more people having a higher standard of living — that’s going to go in the other direction. So we really have to stabilize it at a level that allows ice sheets to remain on Greenland and Antarctica with sizes comparable to what they have now. And that requires that the warming be not more than a degree or so. But the business community really doesn’t understand that.

I remember when we wrote our first paper on this, in 1981, and the New York Times reported it on the front page. I remember saying to one of my co-authors, “This is going to be very interesting, sometime during our careers, we’re going to see these things beginning to happen.”

You probably thought you’d see the world responding.
Yeah! And it worked with the ozone.

Is that just because it was a smaller problem?
DuPont told Reagan it was okay, because they were working on alternative chemicals and could make just as much money at that. That’s what the whole fossil-fuel industry should be working on — alternative energies. But they chose instead to double down on fossil fuels.

* This interview has been condensed and edited. It has also been updated to properly identify Taro Takahashi, and to clarify the precise nature of the argument of the lawsuit.