John Yang: At a climate conference three years ago, Defense Secretary Lloyd Austin said no nation can find lasting security without addressing the climate crisis.

That sentiment reflects the Pentagon's three decade evolution on climate change.

Ali Rogin sat down with a former Pentagon official whose new book chronicles that transformation, both as an eyewitness and as a key player.

Ali Rogin: In 1993 Sherri Goodman became the first ever Deputy Undersecretary of Defense for environmental security.

Since then, she's pushed military and civilian leaders to look at climate change not as a hindrance to the mission, but as a critical component of it.

Her new book is called "Threat multiplier," a phrase she coined to describe how climate change makes every conflict more dangerous.

Sherri Goodman, thank you so much for being here.

Let's talk first about this phrase, threat multiplier.

Why did you come up with it, and why is it such an effective way to describe climate change's effect on security?

Sherri Goodman, Author, "Threat Multiplier": It's a way to communicate to a broader audience the impact of climate change as a force for instability in fragile regions of the world, and how it affects our security globally, that it adds on to all the other threats we already face, from strategic competition to terrorism, weapons of mass destruction, cyber risks, and now we have the instability of a changing climate that acts as a threat multiplier on top of all those other threats.

Ali Rogin: And you really viewed this evolution through your career, when you started the military was much more focused on its impact on the environment, things like cleaning up waste, mitigating pollution, and over your career, it seems like the military's really shift to be focused on the environment's impact on it.

What has it been like witnessing that evolution?

Sherri Goodman: I've seen the military go from being seen as first environmental laggard to today, being seen as a climate and clean energy leader, and you're correct.

In the 1990s at the end of the Cold War, it was a lot about cleaning up messes in the wake of a new era of stronger environmental practices and working to correct problems of the past, but it's also very much about the future, and the future is all about the changing climate.

So now we see how a changing climate affects the mission, the ability to perform that mission anywhere around the world.

Ali Rogin: There are a number of hot wars around the world right now, from Sudan to Israel, Gaza to Ukraine, Russia.

How does climate change act as a threat multiplier in those sorts of conflicts?

Sherri Goodman: Well in drought stricken regions of the Middle East and North Africa, climate driven drought sends farmers and herders to the cities where they then can be recruited by terrorist organizations.

So we say it's a Petri dish for terrorism.

In an increasingly open Arctic because of climate change and rising global temperatures, we now have a region where Putin sees this as a toll road for transportation, from ports in Asia to ports in Europe and China, eyes this as a new region with shorter shipping routes.

So this is an era previously characterized by cooperation that is now increasingly about competition.

Ali Rogin: You've noted how the military has really come around to incorporating climate change into its planning.

What are some instances where they've really done that in impactful ways?

Sherri Goodman: Well, the first I would say, is we now have climate war games happening in every region of the world with every combatant command.

The second dimension of this is we think very seriously about resilience for military bases and for troops, because we can't operate if the base is flooded, or we have to fly the aircraft off in a hurricane because the winds are too strong.

And then third, it's about the energy transition.

How do we move to net zero and still be a militarily effective force.

Ali Rogin: One of the things that I found the most interesting in the book is how different military bases are becoming their own islands of energy independence and resilience.

Can you talk a little bit about some of those efforts that are taking place base by base?

Sherri Goodman: The military has an effort to be net zero by 2050, and to do that, it's deploying microgrids at many military bases.

And the first military base to become net zero is in Albany, Georgia, and it deployed a microgrid, and it has a waste to energy plant, and it's working with the community to enable it to operate net zero, and, in fact, even share energy into the community.

That's because military bases have to operate even if the power goes down on the larger national grid, there's a requirement to operate for two weeks without power off the grid.

So it's very important to be able to sustain that power in a responsible way.

Ali Rogin: You witness this evolution of military leaders who are in charge of deploying troops for these massive missions.

What did you see about how the mindset of military leaders changed when it comes to this issue, and how was that achieved.

Sherri Goodman: You know, the U.S. military, in many ways, is a barometer of change in society, and so as we've seen that over many decades and throughout history, racial integration, women in the military, it's not always at the forefront, but neither is it a laggard.

It's sort of in the middle.

And when it starts to lead, it can really because it's very big with a lot of people, like an aircraft carrier, when that finally starts to move, there's a lot of momentum behind it.

So yes, it took a while, but military leaders figured out that this is where they wanted to be.

They don't want to destroy the environment, and they also want to ensure that our troops, our soldiers, sailor, airmen and marine, are protected from all the threats, including the global climate health threats they now face when they further deploy into hotter temperatures and colder temperatures.

Ali Rogin: You write about how throughout your career, you are often the only woman in the room.

What was that like for you?

And what would your advice be to young women who are looking to get into this field now?

Sherri Goodman: Well, I came of age, you're right, Ali, when there weren't a lot of women in defense, but the doors were opening, and so I kept pushing through them.

And I felt that if I did a good job and I worked on the connections that were needed to advance an important issue, that people would take me seriously and that you could build a coalition of people inside.

I've been a really a change agent from the inside of a very large institution.

And so I want to give young people today, women and men, hope that there are opportunities to have an impact and to have change, even from large institutions.

It takes some staying power, and it takes building that network of people and leaders who are willing to make that change and then make sure it's enduring throughout.

Ali Rogin: The book, is "Threat multiplier."

Sherri Goodman, thank you so much for joining us.

Sherri Goodman: Thank you, Ali, it's been a pleasure.

John Yang: On the latest edition of PBS News weekly a year after the October 7 attack on Israel, an in depth look at how the wars change the region, all that and more is on the latest edition of PBS News Weekly.

And that is PBS News Weekend for this Sunday.

I'm John Yang, for all of my colleagues, thanks for joining us.

Have a good week.