In the debate over how to respond to the perils posed by the earth’s changing climate, the ground has been rapidly shifting in recent years: as the Trump administration has retreated from efforts to curb greenhouse gas emissions and engage in climate diplomacy and public demand for action has grown—particularly among younger generations—cities and states have stepped into the breach.

Last Friday 16-year-old Swedish climate activist Greta Thunberg led the largest of her global climate strikes in advance of today’s United Nations Climate Action Summit, an attempt to spur countries and businesses to step up their efforts at reducing carbon emissions. These calls to action come just days after the Trump administration announced it would revoke California’s prerogative to set its own air pollution rules in a battle over vehicle-emissions standards. Though President Donald Trump plans to withdraw the U.S. from the landmark Paris climate agreement next year, dozens of cities and seven states, along with Washington, D.C., and Puerto Rico, have pledged to shift to 100 percent renewable energy to honor the agreement. The next few years will show whether this is a watershed moment.

During Gina McCarthy’s time as administrator of the Environmental Protection Agency under former president Barack Obama, she spearheaded many of the hallmark climate regulations that Trump is now undoing. Scientific American spoke with her about why she thinks we may be turning a corner on combatting climate change, the work she is doing in her new role as director of Harvard University’s Center for Climate, Health, and the Global Environment and what it has been like to watch as her signature accomplishments have been dismantled.

[An edited transcript of the interview follows.]

Are we, as a society, at a turning point in our willingness to combat climate change? And if so, what do you believe is fueling that shift?

I do think that we are at a bit of a turning point. I think everybody has different views on why that’s the case, but clearly, the science is getting more urgent. I think you have now a new generation of young people—such as [those in] the Sunrise Movement—and they’re just not letting the rest of us off the hook anymore. They don’t seem to have the same kind of reluctance to embrace the science, and they’re seeing that it is their future that is at stake.

There are also a lot of things happening in the world that make climate change much more visible, such as the more intense and frequent storms that we’re seeing—the fires, the floods that we’re seeing. It’s very hard now to ignore it and to think it’s anything like business as usual—because it really isn’t. So I do think there's a lot more ability for people to understand that it’s not just real, but it is really here. It has an ability to impact them.

And I think it’s just really important that we personalize it, and we have found that the health message is a very clear and compelling one. Climate change is the most significant public health challenge of our time. And it’s showing itself not just in the developing world—with millions of people who have water and food insecurity—it’s about the challenges in the U.S. that are becoming very visible to people. It’s showing that health has always been inequitable—both access to it, as well as who is most at risk and most vulnerable. And it’s those communities that are getting hammered by climate change.

All those things come together: It’s greater visibility; it’s more understanding; it’s better science; it’s more solutions on the table. It’s opportunities, as mayors and states and urban and rural communities are starting to step up. The actions that we can take are more robust than they’ve ever been before. And they’re not sacrificial acts; they are better for us economically. So there are lots of reasons why I think people are beginning to get it and admit it and want to do something about it.

We also seem to be moving away from relitigating the basic tenets of climate science to focusing more on solutions. How do you think science can be used to inform those policy questions?

I think the trick is to use climate as a lens in how you look at the challenges of today. You have to make sure that whatever you’re doing for climate, you’re looking at providing immediate benefits—health benefits, as well as economic benefits—and there are huge opportunities there.

And part of the trick is that if you’re going to do that, how do you do it in a way that is more equitable and that brings value to vulnerable communities first? So part of it is not thinking about one thing but thinking of this as a system approach. [During the CNN Democratic climate forum this month, Senator] Cory Booker [of New Jersey] basically said he's going to demand that his entire cabinet looks at their work through a climate lens. That’s exactly what should be done. Why wouldn’t we want to have the military—who totally recognizes climate change as being a huge national and international instability issue—why wouldn’t we want to support it in its interest in having renewable energy instead of fossil fuels? Why wouldn’t we want to become a leader in clean energy, so we’re not fighting about oil fields overseas? All these things provide opportunities for the entire complexion of the discussion to change from “I want to scare you into doing something on climate” to “Let's be smarter about federal dollars being spent and the way in which people are demanding action that’s going to be beneficial for their health.”

So we want to look for where there are the proverbial win-win scenarios.

Yes, because there an awful lot of them. They won’t get you to zero carbon emissions, but they’re building momentum. And they’re providing an opportunity for the private sector to start investing, because it knows people will want it, and people will buy it. Those are the kinds of signals that that have been—how shall I say it?—less clear in this administration than the prior [one]. For somebody that wants a strong economy, [this administration is] doing it in the damnedest way. It is trying to look at what drove our economy from the industrial era and not recognizing that we’re just not there anymore.

What is some of the work your group at Harvard is doing to see which solutions will be the ones that meet those climate, health and economic goals in an equitable way?

We’ve been doing research, in collaboration with a number of other universities, on how we look at the transportation sector. [Along with Washington, D.C.,] there are several states—[in New England and the mid-Atlantic]—that are actually getting together to develop a cap-and-trade strategy. And what we’re doing for them is to take a look at the policies and do an analysis on how you can maximize the health benefits.

We’re also working on some of the rollbacks [of environmental regulations] at the federal level—to take a look at the health outcomes. And we've been able to point out some significant deficiencies in those that we can submit (and have submitted) as a comment so that the EPA can take cognizance of them when it does its final ruling—and if it fails to, then that opens up the potential for litigation against a final rule.

We’re also doing a lot of work in the health care sector—working with medical professionals. They’re beginning to really step up and actually do work in the climate realm. There are things from preventing health problems to looking at where health problems currently exist and how we [can] design solutions that benefit them to how we actually get into the medical profession itself and do work here. [Aaron] Bernstein [McCarthy’s co-director], he’s been really pushing the medical profession to look at things like how heat stress can really do damage to patients if you’re not thinking about the drugs that you give them—things in which the medical care profession itself needs to look at its own work and adjust because of the changing climate.

What has it been like to watch the Trump administration reverse a lot of the key climate change efforts you led while at the EPA?

Well, because you’re taping this, I won’t tell you how I really feel in the most graphic terms. Really, to be honest, it’s very frustrating to keep up with, because [the administration is] doing things gratuitously. On the Mercury and Air Toxics Standards—which is the first limit on mercury emissions from power plants—the major lobbyists for the utility sector wrote to the current EPA administrator and said, “Don't touch it. We’ve completed it. You're going to cause us stranded assets, because we’ll have all this equipment that we’re no longer required to run, and that means we have to pay the bill for it in regulated sectors.” And [the EPA] still went ahead and did it. It’s about emissions of neurotoxins that directly impact fetuses and young kids, and since we did the Mercury and Air Toxic Standards, the amount of mercury being emitted has taken a nosedive. It’s just frustrating to me.

And then [the administration] goes on to do the car rules [to lower fuel efficiency standards]. And the only fun thing about that is it was taking such a drastic sort of rollback on an industry that needs years of certainty to be able to figure out what to make. So you’ve got some of the largest car companies—such as Ford, Volkswagen, Honda, BMW—that have run to the welcoming arms of California regulators. Go figure how a president figured out how to do that. So my head spins.

One of the good things is that [the administration is] very poor at regulating and analysis. It’s looking to get an outcome—not follow the science and not follow the law—which means it has somewhere in the area of an 8 percent success rate in the courts [when rules are challenged].

[The administration also has] an inability to recognize that one of the federal government's best tools to grow the economy—and one of our best tools to remain the strongest economy in the world and compete against China—is not about Paris [the 2014 climate agreement]. It’s about federal dollars being invested wisely in innovation. That’s what the federal government does. There’s always years of a gap between a technology being devised and tested and ready to go and when it gets a significant enough amount of the market share that it’s costs drop, and it becomes truly marketable. That's the gap that’s always been filled by federal dollars. And the really sad thing is while [Trump] is yapping about Paris, we’re seeing China eat our lunch on cars and on renewable energy and equipment. We’re just losing ground, in terms of our ability to grab the clean energy economy and turn it into jobs and economic growth for us.

And that’s perhaps, in the end, the most damaging legacy of this administration: this willingness to look backward and to think that our future is about being oil-independent. It just amazes me that it hasn’t at all recognized where the world is today and where it ultimately will head—whether this president likes it or not.

This story is part of Covering Climate Now, a global collaboration of more than 250 news outlets to strengthen coverage of the climate story.