SOUTH PORTLAND — Twenty-five springs ago, U.S. Sen. George J. Mitchell of Maine put the finishing touches on a book called “World on Fire,” subtitled “Saving an Endangered Earth.” Mitchell had worked extensively on amendments to the Clean Air Act since he joined the Senate in 1980 and now, as majority leader he’d just completed months of negotiating to get a reauthorized Clean Air Act through the Senate.

The book, which addressed what Mitchell called “the gathering environmental tragedy,” sent out a clarion call on the dire ways the Earth’s climate was changing, from rising tides caused by climate change to the hole in the ozone layer and acid rain destroying lakes.

But “World on Fire” wasn’t intended to depress readers; it was meant to stir their blood, make them aware of the full impact of industrialized human life on Earth and make them act.

In January 1991, Scribner’s released the book, which was Mitchell’s first solo venture as an author. There’s a term that veteran writers use for the days immediately preceding a publication date, “Enjoy the calm … before the calm!” they tell a debut author, laughing knowingly.

For Mitchell, it was more of a storm, because his publication date, Jan. 16, 1991, was the same day President George H. W. Bush ordered the invasion of Iraq, Operation Desert Storm, hoping to thwart Saddam Hussein’s plans to expand his dictatorship in the Gulf region.

Mitchell canceled all plans to publicize the book. He never gave a single reading. It had one print run – Mitchell thinks of about 10,000 – and then faded away. He himself has only one copy.

A quarter-century later, we were startled to see how prescient “World on Fire” was, and how despite environmental progress in some areas, we’ve slipped backward – psychologically, certainly – on the issue of climate change. If the world felt on fire to Mitchell then, it certainly hasn’t cooled down.

While Mitchell is so well known (and loved) for his negotiations in Northern Ireland, the Middle East and the world of professional baseball, his work on behalf of the environment tends to get underplayed, so much so that we were surprised to come across the book. As world leaders were in Paris negotiating a pact that will require action on emissions from nearly every country, we sat down with him at a hotel in South Portland to talk about the book that got lost in wartime and why he remains hopeful about the future. The interview has been condensed and edited for clarity.

Q: How long has it been since you looked at “World on Fire”?

A: After you called me, I skimmed through it to refamiliarize myself with it so I have a general recollection of what is in it. But I haven’t reread the whole thing.

Q: Did anything surprise you? So many of the predictions you made have come true, from the statistical, like what the population of China would be today, or the broader, such as how the oceans would be rising.

A: Honestly, to me the biggest surprise is that there are still those who believe, or who say they believe, that there is no such thing as global warming. It was clear to me 25 years ago and the evidence then was far less compelling or as overwhelming as it is now. I just can’t get over seeing these prominent public officials, some of them running for president, saying there is no such thing as global warming. And the chairman of the Senate Committee on the Environment (Sen. Jim Inhofe, R-Oklahoma) saying that global warming is a hoax and a conspiracy.

I could and did understand people who said that 25 years ago, who challenged me and the assertions made in that book, because the evidence was not as clear then. But the events of the last quarter-century have validated the view that the Earth is warming, that man-made activities are contributing to that warming. And that unless we, meaning the people of the world, human beings, take action to drastically slow down emissions, that there will be severe and in some cases, catastrophic consequences for people all around the world.

I don’t think my predictions are 100 percent correct – some of them are more accurate than others – but I think largely what I anticipated would occur has occurred.… It isn’t any longer speculation. It is a reality.

Q: The book opens with you having shepherded a reauthorized Clean Air Act through the Senate. You started in on this as soon as you got to the Senate in 1980 and had been fighting for it ever since. That is a long battle.

A: The conflict continues today in another form and that is on the president’s so-called Clean Power Plan, which is intended to reduce emissions. (The plan is an extensive effort to reduce emissions that has been challenged in court by 24 states, with lawyers arguing that the Clean Air Act, on which Mitchell was the principal author, doesn’t give the EPA legal grounds to enact the plan. He says it does.) Not only should the EPA do something about emissions, they are required by law to do something about emissions. And so it is particularly unfortunate that we now have this rear-guard action of trying to prevent implementation of a major step toward dealing with the issue of global warming and climate change.

Q: What is the most frustrating aspect of climate change denial?

A: There is this constant effort by those who oppose environmental protection to cast it in either/or terms – you either have economic growth or you protect the environment, you can’t do both – but the fact is, we can do both and we have done both in this country.

Our economy hasn’t collapsed in the past 25 years since we passed the Clean Air Act and we have been able to protect the health of the American people from air pollution and water pollution at the same time that we have had substantial economic growth – with some ups and downs as we always have.

As the president has said many times, moving to an energy structure that is less reliant on fossil fuels and carbon can be a source of economic growth. Clean energy is an industry in and of itself and you can create jobs doing that.… There are tremendous economic opportunities in solar power and all the rest of it (green energies). Nobody can doubt that over time electric cars are going to replace gasoline-fueled vehicles. The only question is, is it going to be 50 years or is it going to be less or more?

Q: And will we have moved completely away from coal-fired electricity?

A: Many, many are now switching to natural gas. Natural gas has its own consequences, less severe but different.

The maxim I like to keep in mind is that the solution to every human problem contains within it the seeds of a new problem. And what it requires for societies to succeed is flexibility, innovation and a willingness to adapt, all of which requires greater research, more science, more knowledge.

One of the most disturbing things about the political debate in the United States today is the extent to which it is an effort to deny science, to deny the obvious in search of a mythical past, which is viewed through rose-colored glasses as if there weren’t problems at that time.

Q: Are you encouraged by what you see happening in the sustainability movement in Maine? Would you have expected, for instance, our passion for local food?

A: If you grow up in Maine, you by definition spend time with nature. I would guess almost every Mainer has been in the woods and hiked and been on the coast and been on our inland lakes and it is part of our lives. Maybe we have a more ready acceptance.

Secondly, I think politically there have been strong and effective political leaders, both Democrats and Republicans, who have recognized the importance of environmental protections.… In the Republican Party (now) there are very few voices of what I would call moderation on the issue of environmental protection. Luckily we still have them in Maine. Sen. Collins and Sen. King and of course Rep. Pingree are outstanding advocates of protecting the environment.

Q: You wrote a lot about acid rain in “World on Fire,” and that’s one of the pieces of good news, we’ve managed to roll that back, thanks to emissions controls. Now we worry about ocean acidification, particularly right here in Casco Bay. It’s different, but …

A: There is no perfect solution that will solve all of our environmental problems in a single bit of legislation or a single policy or a single approach. Life is change. And you have to think of it as managing a steady flow of change and events. Take for example – this is roughly analogous – every civilized society has laws against murder and other forms of crime. There is not a single person I am aware of that believes murder and crime are going to end. They are part of life, part of human nature. So we do our best to manage it, to limit it, to prevent, to deter, to punish it when it occurs.

And we recognize that there is an ever-changing nature, and we have to keep abreast of it with changes as we acquire greater knowledge of the causes and consequences of our actions.

What matters most is the state of mind of the society. There you really do have two sharply diverging choices: angry, frustrated, clinging to the past, denying science, resisting change – always and ever a prescription for failure. And on the other hand, encouraging and accepting science, open minds, encouraging research, innovation, more and better education so you not only have people who are trained and adaptable to the work needs of the future society but also people who are better citizens.

Q: What about the growing numbers of people in general? What do we do about overpopulation?

A: Among the main factors that affect population growth, none is more important than the status of women. Where women are fully independent and empowered, populations tend to stabilize unless increased by a surge in immigration.

Where women are not independent and empowered, populations grow rapidly. Most recent U.N. estimates are that the world’s population, now at 7.5 billion, will peak at 11 billion at the end of this century, 85 years from now. The U.S. population, now 320 million, will reach 440 million by 2050, just 35 years from now. So that means we face tremendous opportunities for growth and prosperity and tremendous challenges.

We have to accept the reality of change and figure out the way to give everybody a chance to succeed in our society. And I think it is possible.

Q: So you remain hopeful?

A: Very much so. I got married late in life, and I had children late in life, I have an 18-year-old son and a daughter who will be 15 in a few weeks. And I tell them they are going to live a much better life than I have because our society is progressing in so many ways.

Q: And despite all the obstacles we face from climate change, is it gratifying to look back on your work on the Clean Air Act of 1990? You’ve said that it wasn’t as strong as you originally hoped, but compromise was needed to get it passed.

A: The Natural Resources Defense Council published a detailed report (in 2013) estimating that a very large number of people have lived longer, in the millions, as a consequence of the benefits of cleaner air, and there have been far fewer people suffering from respiratory and other ailments. It is indeed very gratifying. And I think that is especially true when you come from Maine. Look out the window now. How lucky we are.