Last month, President-elect Joe Biden said he would demonstrate his administration’s prioritization of the climate emergency by appointing former Secretary of State John Kerry to a high-profile role as the nation’s climate czar, a new position on the National Security Council that will report directly to President Biden, and through which Kerry will elevate the climate crisis in both the nation’s international diplomacy and its domestic policymaking.

Since the election, Kerry has said little about what he will do first, or what he believes a Biden administration’s highest priorities should be.

Earlier this fall, in the course of reporting for an in-depth series about a great global climate migration, I spoke with Kerry twice about the current state of the climate crisis, and its implications for the United States and for global security. In our conversations — the first streamed for the public on Sept. 10 through Kerry’s climate-focused organization World War Zero, and the second a private on-the-record interview Sept. 30 — we discussed his outlook on climate policy, the potential for warming to drive a mass global migration, his thoughts on immigration policy and what a new Biden administration might begin to do about it all.

Kerry spoke about the climate threats in unusually frank terms, portraying a crisis of catastrophic proportions demanding an urgent response. The following is a portion of our conversations, woven together and edited for clarity and brevity.

What’s the connection between climate change and human migration? You’ve been talking about this since you were secretary of state in 2015.

They’re integrally intertwined. I mean, this is not some pie-in-the sky future dilemma that we may face that people are talking about hypothetically, it’s already happening, and it has been happening for some period of time, and the linkage could not be more clear. We had 130 degrees in some communities in Pakistan last summer, also in the Middle East. We had 130 degrees in Death Valley in the United States. If places keep getting hotter like that, and fires keep devouring communities and so forth, places are going to become unlivable and people will migrate, period. And so people are going to move to places where they think they can live. They’ll fight over places that they want to move to. We will have millions, tens of millions of climate migrants.

In Syria, this was not the cause of the Arab uprising, and it was not the cause of the Civil War, but it contributed very significantly to the intensity of the war when a million plus people moved in from the desert where they no longer could raise their livestock, they no longer could live. They came into Damascus, and anyone will tell you that that contributed very significantly to the capacity for the unrest and insurgency that followed. I personally thought that the pressure of migration on Europe during the Syrian crisis was the great warning sign for everybody. That’s one country’s upset. The one group of people being relatively managed in their dislocation. But if it’s a massive movement of people, all of a sudden?

You can have wars that come from this migration as people fight for waterholes, as they fight for a homestead. You will have massive pushback by people in various countries that can amount to genocide. I think it is very clear that if we’re going to try to reestablish a means of managing the affairs of state and of the planet and dealing with global issues, we’re going to have to deal with this.

The pressure on borders, then, will be immense.

It could be very tense. Without proper leadership and without a lot of forethought and without an inclusivity to a process where people feel they are being heard, this could be a really, really messy process. I mean borders will be challenged. Societies will be challenged. There will be the nationalistic populism we see today, it will raise its ugly head in various countries and who knows where it goes? Remember what happened in Rwanda. If people are thrown together, all of a sudden that can get pretty ugly if it isn’t managed.

Climate has already been a driving factor for migrants coming to the United States. What are the implications of a future with even more people, as the climate warms, and how do you think a Biden administration would approach it?

The United States is a country — and I believe will remain a country — that will continue to welcome people to our shores through legal immigration. And legal immigration is the key. We’re having a huge political battle over that now. We’ve been stalemated on this issue, polarized for years, and we’ve seen how divisive and dangerous it is to our own country. We’ve had vigilantes — people going down as part of so-called national militia and reinforcing our border. You can imagine if 30 million people are trying to move in. I don’t think that’s going to happen because I think we’ll have a sensible policy between us and Latin America.

When Joe Biden was vice president and I was chairman of the Foreign Relations Committee, we were very involved with the Central American presidents of countries to help deal with the problem, particularly of child migration, which was coming about because of the violence, because of the lack of opportunity, because of the lack of education and so on. So we put together a plan, not unlike the plan we once put together called Plan Colombia, where we put a billion dollars on the table and managed to pull Colombia back from being a failed state. You can’t just talk about it, you can’t just exploit the idea of the emotions that go with it, and the building of a wall, which Donald Trump has done. You have to do something about it. And doing something is not just building a wall or trying to build a wall, it’s helping to provide an alternative life for those folks, helping to provide alternatives where millions of people will make a different decision. That’s critical to what we have to do.

But if we’re going to grow as a nation and our economy is going to continue to grow, we’re going to continue, I think, to have legitimate immigration, because that’s been the staple of our economy. The folks who come in beginning at the bottom of the ladder are the ones who have helped to build America in the best sense of the word, and they do a lot of jobs that other people just won’t do.

Are you saying you’re for open borders?

It’s a really important question. Democrats have been, I think, not as thoughtful as we might be in the language we’ve chosen and the ways that we approach this. I believe in borders. If you don’t have borders, you don’t have nations.

Now, that doesn’t mean you shut down immigration, you shut people out. You’ve got to deal with it so that people know they can legitimately find a way to be able to immigrate, and that we have a legitimate control of the border. You do have to have border enforcement. That said, you also have to have a humane and fundamentally fair system where people who came here 30 years ago, the dreamers, many of them, they played by the rules, they paid their taxes, they haven’t been arrested, some of them doing better for our country paying into Social Security and other things than other citizens.

So we have to stop exploiting the issue and get that pathway to citizenship that gives everybody a sense that the system is fair. And it doesn’t become an incentive for more people to break down the door and come in illegally. I think you can balance that.

All right. And you were saying, this is about more than North America.

The solution is not going to come by just dealing with this problem of people from Central America. This is a global problem. Eighty-five percent of all the emissions in the world are coming from 20 countries. Over 50% of all the emissions of the world are coming from three entities; the United States of America, the EU and China. Over 50%. So those are the countries, frankly, that have the greatest responsibility to move rapidly to do something. And we did that in the context of the Obama administration where we had what we call the Major Emitters group and we came together to talk about what we need to do.

But here’s the problem. Despite Paris, despite all the best intent, it’s just not happening. If you did everything that we laid out that we needed to do in Paris, we would still be rising 3.7 degrees centigrade. That’s catastrophic. But we’re not doing everything we laid out in Paris, so we’re going way beyond 3.7 degrees right now. We’re heading to 4.1 or 4.5 degrees. That is just such a catastrophic impact on our biosystem and on our planet that it’s hard to even describe to people.

So the United States has to step up again. We have to do what President Obama licensed me to do, which was go to China, sit down with President Xi and talk about mutual interests. Now, China is about to bring 21 gigawatts of coal fired power online. India is poised to do slightly less, but similarly huge amounts. That’s going to kill us. That’s going to kill the efforts to deal with climate. If we don’t get China on board to help us lead all development efforts over the next years, and then India and Brazil and a group of other countries, we’re not going to get this done. I’m just telling it like it is.

What’s the geopolitical long view? Do you see countries moving strategically to try to benefit from climate change?

Yeah. That’s manifested in the Arctic where you see competition for rare minerals and mineral exploitation, as well as claims being made about the opening of the Northwest Passage. Russia and China are beginning to get very aggressive in their hunt for commodities for the long term. That plays out differently as land mass changes its accessibility or its usability. [Migration, then] follows that. You’re going to have a bunch of nation states that are going to disappear over the course of this century. Who’s going to welcome them? What countries will they go to?

It’s possible, then, that the climate crisis writ large just becomes a new political wedge?

Some are already exploiting it. The greater threat is that if you don’t deal with climate, soon, rapidly, you will have a whole bevy of politicians who are exploiting the negative consequences of not having done so. So it’s not that you’re suddenly going to turn around and everybody will sing “Kumbaya” and respond to go get the job done. Don’t just blame China, or blame Brazil, or blame somebody else. We will have a nationalistic populace rising which will, I think, obscure much of the real debate that people need to have about health care and education and opportunity, and so forth. It will really get, I think, into an exploitative period.

The solution to climate change is energy policy, and energy policy is opportunity. If we will get about the business of being the world’s greatest innovator and the world’s greatest creative entity. This is our modern-day race to space.

Let’s talk about Asia for a moment. The U.S. relationship with China is increasingly adversarial. But China is key to solutions on climate.

Part of the increasing tension between our countries is created by President Trump. I think China is having a lot of difficulty figuring out his approach to trade. He just went straight to tariffs and straight to a trade war. I think the Chinese have very little use for our president, frankly. I think China is going to be, like it or not, one of the most important relationships that we work on over these next 10, 15, 20 years or longer. The point is, you’ve got to talk to people. You can’t run around the world bashing people and behaving like all you have to do is tell them what to do. So we’re going to have to reach out, build up, but also be absolutely firm about things that we disagree with.

What about Russia? Putin has said he wants to use climate to become a food-producing superpower, and he might need a lot of climate migrants to do it. China has been aiding these efforts, apparently eager to strengthen a new climate-era axis of Eastern power.

If Russia thinks that climate is going to benefit it, they haven’t done their calculations about Siberia and permafrost and tundra thawing and what the impact of methane is going to be on damaging the rest of the planet. That’s just not a thought-through concept.

Is there a competitive or security interest that the U.S. has in how Russia approaches the challenges of climate and migration?

Of course. I mean there are major security interests in what Russia decides to do. I mean how Russia responds to the challenge of climate is going to be critical. One of the great challenges is that Russia is an extraction-based economy, whether for fossil fuels or for minerals. The question looms large as to how serious Russia is prepared to be about contributing to resolving the final crisis. As long as the agriculture they’re employing, they grow and harvest it with sustainable and regenerative practices, that could be terrific. I mean there’s not exactly a surplus of food for lots of populations in the world.

Bring us back to the United States. We’ve seen record heat, fires and hurricanes this year, and early signs that climate change is displacing people here, within the United States. Do you think this nation will look different in a warmer world?

Yes, it will. There’s going to be some measure of disaster in that transformation, because various places will not be habitable. Smaller cities may become bigger, we may wind up with better, more modern design; Our school systems, transportation, et cetera. This is an opportunity to build sustainably for the long term. I don’t see it as all tragedy at all. I mean, yes, there will be tragedy associated with it. It’ll be hard for some people to give up homesteads and move away. But there are some farmers who just can’t survive where they are now already. So yes, life will be different, but it doesn’t have to be worse.

So what happens next? And how do you believe a Biden administration would take on these challenges?

We can manage much of this. If we get ahead of the curve and getting ahead of the curve means building out infrastructure that adapts and mitigates. It means helping populations to harden their physical structures, to be able to manage whatever the transformation is. It involves really trying to take seriously what the scientists have said.

The scientists gave us 12 years three years ago. We’ve squandered those three years. We had 70 degrees in Antarctica. If we don’t take those warnings, we’re doomed.