The U.N. secretary general has called 2021 the “make it or break it year” for global climate action. Scientists say the world must cut its greenhouse gas emissions nearly in half by the end of the decade to avoid the most catastrophic impacts of climate change. Yet the world remains on a trajectory to blow past dangerous thresholds countries promised not to cross.

As leaders from nearly 200 nations prepare to gather in Scotland for the critical U.N. climate summit known as COP26, Secretary General António Guterres sat down with The Washington Post at U.N. headquarters in New York. He spoke about what is at stake next month in Glasgow, the mistrust between developed and developing nations, and what lessons the coronavirus pandemic offers for climate change.

Here are excerpts from that conversation, edited for length and clarity:

Q: You’ve talked about climate change passionately and bluntly, and the need for countries to do more to meet this moment. You’ve not always hidden your frustration or your disappointment when that hasn’t happened. How are you feeling ahead of the U.N. climate summit in Glasgow?

A: If I look back into my 72 years, which was essentially in politics or public service, this is the most important political battle of my life. In this context, I am looking at COP26 on one hand: extremely worried. On the other hand: still hopeful.

Why extremely worried? We see the impacts of climate change accelerating, and I don’t need to go on describing all the disasters and situations around the world that demonstrate that the planet is changing by the day. If the next decade goes wrong, we will have a number of tipping points and points of no return.

I am extremely worried because I have not seen the movement and the ambition that is necessary to reach targets compatible with [keeping postindustrial global warming within] 1.5 degrees [Celsius].

There is a level of mistrust that is worrying. Mistrust between the large developed countries and the large emerging economies, and mistrust in general between the developed and developing world. Developed countries were not able up until now to implement, or even to present, a set of commitments that guarantee the implementation of the $100 billion in support to developing countries per year that [was promised] to start in 2020.

People in the developed countries say: “Well, we have done our bit. We have now committed to net zero in 2050″ — even if there is a question of credibility of many of those commitments. “Now it is time for the emerging economies to do the same.” But based on the principle of common but differentiated responsibilities in the Paris agreement, developed countries need to do it before 2050 to allow emerging economies to do it after 2050.

So I’m worried, because if these things do not change between now and Glasgow, Glasgow can become a missed opportunity. And we have no time for missed opportunities.

But I’m still hopeful. Because I see that there is a growing consciousness that we are really at the verge of the abyss.

Q: I’m curious about your own journey on climate change. You were the prime minister of Portugal. You worked on refugee issues for the U.N. Since you became secretary general [in 2017], how did you decide to talk about it and to press countries on it? And in your life or your travels, have you seen impacts that shifted your thinking about climate change on a personal level?

A: It has been a concern for many years. In my time in government in Portugal, we approved legislation in relation to renewable energy, with an obligation for the grid to buy all renewable energy produced.

So, I mean, this is something I was always conscious of.

But, of course, now I have a global responsibility. And I’ve seen the impact of climate change in the movement of people. I see more and more people forced to abandon their communities, to move from their areas for the simple reason that life is no longer possible there, and I see the interconnection of climate change with poverty, but also with insecurity and with conflict. I see how terrorist groups take profit in the divisions between farmers and herders at the lack of water.

I strongly believe this is the biggest risk that we are facing as a world community, and this planet.

And when I look at my granddaughters, who will very probably [live] to the end of the century, I wouldn’t like them to come to say that the planet is hell, and that I have not done enough to avoid it.

Q: What would you want them to be able to say?

A: That finally, a few decades ago, there were some generations that understood that we were moving in the wrong direction and allowed us now to live in a world in which the peace with nature is creating the best possible conditions for human beings to inhabit planet Earth.

Q: You were the first secretary general who was an elected leader of a country. How sympathetic are you to the various domestic pressures each country faces?

A: When we want to do a reform, and you know that society will have resistance, you need to be smart. I’ll give you two examples.

I am strongly in favor of a carbon tax. The carbon tax will increase prices. The carbon tax will be unpopular. So what I’m always advocating is to say: “Let’s shift taxation from income to carbon. So let’s have a reduction in the taxation of income equivalent to the increase in the taxation of carbon.”

In some societies — I’m thinking about fishing communities — the subsidies to gas/oil, to fossil fuel, are important for their life. But instead of subsidizing fossil fuel, you can subsidize small fishermen.

We need to be able to understand that in any transformation, there are winners and losers. I know that the green economy will create many more jobs than the brown economy. But I know that some people will lose their jobs when their coal mines close.

And we need to make sure these people understand that the government and the other authorities care for them, will provide them with alternatives in training and will guarantee their social protection.

Because to say “we have a net creation of 1 million jobs” doesn’t make happy the one that lost the job.

And the truth is, when one looks at the evolution of public opinions and the political atmosphere in countries, 100 people angry have much more influence than 1,000 people that are happy. Especially because those that are happy consider it natural, and those that are angry are really angry.

Q: Do you spend much time thinking about what more you could be doing on climate? What kind of frustration is there in not being able to compel more action? You have a big platform but also many limitations.

A: There are many illusions about what the secretary general of the United Nations can do. I am a strongly committed multilateralist, but I recognize that our multilateral institutions — if you allow me to use an expression that I use many times — lack teeth. And sometimes, even if they have teeth, they have shown little appetite to bite.

We, as the U.N., need to be able to provide leadership. Unfortunately, in the world, power and leadership are not always aligned. Sometimes there is leadership where there is no power, and there is power where there is no leadership. And I think there is a strong risk that might happen in relation to climate change.

Q: How do you view the U.S. role on climate change? The country left the Paris agreement under the Trump administration. President Biden has made it a priority again. And Congress has yet to fund what he wants to do. Where do you feel there is trust or lack of trust for the U.S. on climate right now?

A: The fact that a policy has changed dramatically — twice, with changes of president — is not good for the trust that other countries can have in one country. But that is the reality in democratic life, and we need to accept that reality.

I think that the measures proposed by President Biden — and let’s hope that they will go through [Congress] — represent a solid commitment to the reduction of emissions.

Unfortunately, the U.S. has not yet assumed what would be its fair share in relation to support to developing countries. And also, I think the U.S. has not yet given enough attention to adaptation in the developing countries.

Q: You’ve spoken a lot in tandem about the coronavirus pandemic and climate change. These are obviously crises you’ve been dealing with — the world has been dealing with — simultaneously in the last couple of years. How has one affected the other? And are there lessons learned from one that you can apply to the other?

A: Covid has created a number of serious problems to economies that might make it more difficult to accelerate measures to fight climate change. But what covid has demonstrated is the enormous vulnerability of our global governance systems, the enormous vulnerability of our planet and of our societies.

And that is a wake-up call. And that wake-up call, I think, is working also for climate, at least in large sectors of public opinion.

The fact that there has been an extremely inequitable distribution of vaccines and that many developing countries still have a small percentage of the population vaccinated [is not good].

And the problems of debt and the absence of an effective mechanism of debt alleviation for many countries in distress — all these have helped to create this sense of inequality and injustice. It increases the mistrust between north and south, and this increasing mistrust between north and south is not helpful when we discuss climate change.

Q: Can the Paris agreement move as fast as climate change is demanding that the world move?

A: The Paris agreement is flexible. It is not a mandatory treaty, as you know. But the Paris agreement is not a static agreement. It is an agreement that foresees an evolution with increased ambition. And so, what we need now is to accelerate those mechanisms to increase ambition.

Q: If the world does not muster the commitments that you would like to see in Glasgow, I assume you don’t think that’s the end of the story. What comes next?

A: The next day, we start again.

Never give up. But, having said never give up, it’s not good to miss this opportunity.