Michael Oppenheimer has been thinking about climate change about as long as most Americans have been alive. For almost four decades, he has worked on answering the phenomenon’s two most pressing questions: How dangerous will climate change get? And what can humanity do about it? So after President Donald Trump announced his decision to withdraw from the Paris Agreement on Thursday, Oppenheimer was one of the experts I most wanted to hear from.

It helps that Oppenheimer, a Princeton professor since 2002, has worked on or in some of the most important environmental programs of the modern era. He is currently a coordinating lead author of the UN Intergovernmental Panel on Climate Change, and he edits the journal Climatic Change. From 1981 to 1996, he worked as the senior scientist at the Environmental Defense Fund, where he helped frame the 1990 amendments to the Clean Air Act that reduced acid rain.

Along with other scientists, he lobbied the United States to start negotiating the UN Framework Convention on Climate Change, which President George H.W. Bush signed 25 years ago this week. Since then, he has attended the major UN climate negotiations, including Paris in 2015.

I spoke to him on Friday about his outlook for climate treaties looking forward, Trump’s ability to roll back older climate policies, and whether the U.S. withdrawal from Paris could make global warming significantly worse. Our conversation has been edited for concision and clarity.


Robinson Meyer: You’ve been involved in climate diplomacy for a long, long time. How are you feeling today?

Michael Oppenheimer: I’m upset and troubled—as I rarely am, because I’ve been involved in this issue for 35 years. I’ve seen a lot of ups and downs, but this is the most discouraging. It is more discouraging than when George W. Bush withdrew from the Kyoto Protocol.

The reality is the clock has been ticking all this time, all those 35 years the clock has been ticking. And because the clock has been ticking, Earth is already a degree warmer than it would otherwise have been. We don’t have much time to avoid the two degrees of warming that would destabilize ice sheets, entail extreme heatwaves, and potentially undermine food security. And this decision is just enough to push us over the edge, in my view. I think it’s totally unrealistic now to believe that we are going to meet that objective.

So in a personal way, for someone who has worked on the issue for decades, this more so than any other setback seems to indicate that it’s highly unlikely that we can make the two-degree goal. The Trump action pushed us over the edge, and basically Trump owns the responsibility now for this problem.

Meyer: Do you think it’s the withdrawal from Paris that puts us over the edge? The Trump administration has already cancelled a lot of the Obama programs to reduce greenhouse-gas emissions—are those more important?

Oppenheimer: No, I don’t think that cancelling domestic regulations will actually have as much effect as the withdrawal from Paris could. I am fairly confident it’s going to discourage some other countries from being aggressive in their commitments.

The two do go together, they’re of a piece. But, in fact, there is no immediate effect from some of the work the Trump administration has done on the Obama regulations. Because you can’t just cancel them. Even with the Clean Power Plan—if the courts determine that the plan is legal, then it will take years for the adminstration to rewrite it. They can slow down implementation but they can’t eliminate it. Also, a lot of the momentum in the markets—in terms of low prices for solar and wind and natural gas—is going to continue, no matter what.

But the point is: All that wasn’t enough. We needed a ratcheting up of stringency over the next decade or so, if we were going to be assured of meeting the U.S. plan under Paris—and certainly if we wanted to go beyond that and keep decreasing emissions at an accelerating pace.

Meyer: And what’s the mechanism there? How does the U.S. leaving the treaty affect the behavior of other countries?  

Oppenheimer: Two ways. There’s a direct way in terms of lower contributions to the Green Climate Fund—it sounds like we’re not going to give anything to that fund anymore. That will actually inhibit some countries—particularly newly emerging economies—from being able to invest in some of the technologies that would bring their emissions down.

And the second way is this: Some of those very same countries are newly emerging—not just in terms of their economy, but in terms of their attitude towards climate change. Those countries are not so sure they want to go ahead with a climate policy, and they need encouragement. So you’ll see, I think, countries like India, Vietnam, the Philippines, Indonesia, Brazil—all of which have other problems that probably come first—you’ll see a lot of them backing off the seriousness with which their commitments are pursued and implemented.

Now, some of this stuff they may want to do anyway. India, probably, is going to come around to dealing with its air-pollution problem, like China is doing. In the process, it will deal with some of its greenhouse contribution.

But the Trump action can’t actually have any positive effect on any of that. I don’t believe the arguments that the rest of the countries are going to buckle up, redouble their efforts, and compensate for the absence of U.S. leadership and participation. I think the immediate consequence will be a ripple effect, making countries think twice about doing much about climate change. It won’t be China or Europe. It will be a lot of countries whose economies will exert substantial leverage on global emissions over the next 10, 20, 30 years, as they grow—those are the ones that I expect to hesitate. And that hesitation, in and of itself, could be enough to condemn the two-degree target to oblivion.

Meyer: A lot of people would respond to that: Well, Paris was already symbolic, so what difference—

Oppenheimer: That would be wrong. Paris was far more than symbolic. Paris didn’t have a hard ironclad binding requirement, except to submit new plans, and I criticized it for that at the time. Paris did not have hard obligations and penalties, like the Montreal Protocol on ozone depletion did. There are no trade sanctions in Paris. All that made it a relatively soft agreement.

But nonetheless, that’s the furthest countries were willing to go. And within that context, it held promise. I think we would have wound up in a situation where commitments [to reduce carbon emissions] would have been met at probably the lower level, but a heck of a lot more would have been done than if Paris didn’t exist at all.

And then we could also have used the name-and-shame game: the business of having to report your emissions under a transparent system, and say what you did and what you didn’t do. And that technique is effective in some international circumstances, like human rights treaties. It’s not like there was nothing there.

Meyer: You just mentioned a “transparent system.” I’ve heard American diplomats be concerned about transparency now that the U.S. is out of the treaty. What would make Paris a transparent system?

Oppenheimer: Paris doesn’t have a clear set of provisions yet on what’s called “transparency.” Those were critically important, because those are the provisions for monitoring, validating, and reporting emissions, which make the whole thing clear to everyone and make other countries trust that you’re doing what you said you would do. Those are still in the process of development, and we don’t know how those negotiations will turn out. But with the U.S. out, it’s much more likely they’ll turn out badly, because China doesn’t like transparency and the U.S. did. If for no other reason, the Trump administration should have stayed in Paris to make sure that China doesn’t create a set of rules that let countries obfuscate what they’re doing, which is generally China’s tendency.

Meyer: There’s another counter-argument I’ve heard to staying in the agreement—that China and India issued plans that were largely what they would have done anyway. That renewable prices are falling, and these countries want to combat air pollution, so they just submitted plans describing what they would probably do without Paris.

Oppenheimer: Well, it’s the same for the U.S., by the way. We just codified what we were going to do under the EPA regulations that Obama was planning to implement.

Meyer: The argument, I think, is that the Clean Power Plan required a more ambitious change in the pre-existing U.S. electricity sector, but China and India benefited because they’re building all of their infrastructure from scratch.

Oppenheimer: I wouldn’t say that’s true for China. China’s had an industrial revolution, and part of it is aimed at renewable energy—and making money off other countries, by the way, including us. China is now the leading purveyor of photovoltaic cells and wind turbines. All this is all fitting into a pattern where China gets to fix up its air-pollution problem, reduce its dependence on coal, sell stuff to the rest of the world—and, in the end, fix up part of the climate problem.

So it made sense, and it was credible, that they would move forward. And in fact they have an interest, to some extent, in making sure other countries move forward because they want to sell the equipment to them. But India is one of the countries which is iffy. There’s no doubt about it. They may or may not come forward.

So it’s a different situation in different countries. I think, when you take it together, you see Paris—if it’s operating with transparency—as a framework which allows countries to really see what other countries are doing. And it’s that public forum, that knowledge sharing, that confidence built between countries that actually is the value of Paris. It’s not binding, but it’s the trust that’s instilled, and the desire to not get too much criticism at the international level for non-performance. That was worth something, and that’s what’s been lost.

Meyer: Something that I’ve heard allusions to, that’s been a little hard for me to pin down, is that China has this whole scheme going that you just described. They’re fixing their air-pollution problem, they’re getting better at making solar panels, and then they’re selling that infrastructure to the rest of the world. Do U.S. companies miss out by not having something similar?

Oppenheimer: Yes, so U.S. companies miss out in three ways.

Number one: This is bound to soften the U.S. demand for low-carbon technologies, across a whole variety of fronts. That ranges from Elon Musk’s electric vehicles to the possibility that the U.S. will never develop a major photovoltaic or wind-generating company again. So it softens the prospect for U.S. innovation and increase the likelihood that we’ll be buying from China. Because no matter what, China has this big domestic market, and that’s the basis of their industry and allows it to have a big export industry.

Number two: It’s going to drive industry crazy, eventually, because about half of the states are going to go ahead and build a crazy quilt of regulatory requirements. And companies hate that. That’s why companies—no matter what they say about the government—love the federal government, because it brings regulatory uniformity. But what you’re going to see instead is the states going ahead, and companies having to meet 50 different requirements in some cases.

You’re going to see some of these companies come back and actually plead for some level of regulatory uniformity. They may not want as much as I do—but they’re going to want something.

Number three: Look to the Europeans to start threatening what they’ve talked about many times, which is border tax adjustments to compensate for the fact that the U.S. doesn’t have a price on carbon. I don’t see it as necessarily likely, but it’s in the air and it could happen and companies aren’t going to like that either.

Meyer: Earlier, you alluded to George W. Bush’s decision to withdraw from the Kyoto Protocol in 2001. How is this different from Kyoto?

Oppenheimer: Let me frame that by saying that the speech Trump made yesterday was about Kyoto. He wasn’t talking about Paris. I don’t think there was one thing about Paris.

Meyer: Yeah, it was all these recycled arguments that actually applied to Kyoto.  

Oppenheimer: It’s all bullshit. That’s all there is to it. But it was a speech that could have been written—that was written—by industrial lobbyists twenty years ago. It was the same criticism they made of Kyoto, but Paris is entirely different than Kyoto.

For Paris, the world’s countries had finally gotten together in a framework that had allowed each, in their own way, to find a pathway to reducing their greenhouse-gas emissions. All the important emitters had indicated that they were willing and eager to do so. And that was a major step forward, because previously—in the UN Framework Convention or the Kyoto Protocol—significant emitters were either left out of having any obligations, or they clearly weren’t serious in what they would do. But [Paris] had a level of seriousness that was credible.

Another way that Paris is different is that, in some ways, the Kyoto Protocol was premature. China was growing fast [in 1997], yet it hadn’t grown to the point that it was inevitable it would agree to some sort of emissions reductions. And because it hadn’t come to grips with its air-pollution problem yet, and because the climate problem hadn’t matured in China yet, it wouldn’t agree to binding limits on emissions like the U.S. did.

If it had been five years later, and if there had been a different U.S. administration, a different agreement might have been negotiated. China might have been part of it, and it might have survived. But Kyoto was developed at a time where the configuration of countries was such that it really didn’t have much chance of survival.

What’s different now is that an agreement like Paris should have a chance to work, and there’s no reason the U.S. should have pulled out. We had something that got everybody on board, and with Kyoto we didn’t have everybody on board. That’s why this is a more devastating blow. Things were really set up in a way that could have worked.

Meyer: Did you think when we were negotiating the UN framework convention—I guess that was signed almost exactly 25 years ago—did you think it would be 2017, and we’d still be having these kinds of domestic policy fights about climate change? Or there would still be this level of polarization?

Oppenheimer: No—I mean, I don’t remember what I actually thought.

But in trying to reconstruct, I do remember thinking that, about 10 years after the framework convention, there would be a solid international agreement in place. It would be a protocol to implement, in a binding way, the obligations that were necessary to start turning the curve around on emissions. And if you asked me what I thought would happen 25 years later—where we are now—I would have thought global emissions would have been well on their way to stabilizing, and we’d be decreasing emissions around 2030.

In some ways, there have been a lot of surprises along the way. The rise of China came after the framework convention—you know, people sort of thought it would come, but no one thought it would accelerate as quickly as it did. On the other hand, the global peak in emissions may have already happened. The last three years, global emissions have actually stabilized and declined a little bit.

I was the chief scientist at the Environmental Defense Fund in the early ’90s, and I remember one of the board members standing up and saying that we should have a goal for the organization: “No Coal After 2030.” And a lot of people said, that was great, but it wasn’t going to happen. But if you looked today at making a global no-coal commitment, you wouldn’t say 2030, but if you looked at what’s necessary to avoid two degrees, you might say 2050.

Meyer: Did you know it would be a life’s work in 1992?

Oppenheimer: I think I knew this was going to be a life’s work from when I took up the problem, which was basically 1981.

When I took it up, I knew it was so big and I was only one person—I’m a cog in the gears for God’s sake, and I’ve never had any illusions that I was going to solve the problem. It will take millions of people. I just thought: ‘This is such a big problem, and I’m going to be working with other people on this problem probably for the rest of my professional life’—and that’s the way it’s turned out.

And it’s great! It’s a fascinating problem intellectually, and if we had all the time in the world, it would be terrific: Today’s setback would just lead to tomorrow’s advance. The trouble is the clock has been ticking, and we’re running out of time to avoid very serious consequences, some of which have already started to occur.

So when you see someone come along and sort of cavalierly, with a mouthful of lies, just sort of blow off the latest incarnation of progress on this issue, it can be temporarily discouraging, very discouraging. But look: I’m sure humanity is going to muddle through. I’m sure that relatively well off countries, and relatively well off people, will muddle through. I’m very worried about people who have less resources, countries that are poor, and the whole natural world. All those are the ones that suffer first. Of course, all of us, eventually, are going to suffer if we don’t bring this under control.