Jane Fonda says climate change is singularly vital issue after decades of activism: 'This is the future of the entire planet'

Fonda says climate change is the most urgent issue in decades of her activism.

For every Friday of fall 2019, Jane Fonda was on Capitol Hill, protesting climate change alongside friends like Gloria Steinem and actresses Rosanna Arquette, Sally Field and Catherine Keener.

Fonda could spend her time in retirement, enjoying the fruits of an illustrious Hollywood career. Instead, on the eve of her 82nd birthday, she was led out of the Hart Senate Building in handcuffs. She had been arrested for civil disobedience.

Since September, Fonda says she’s “lost count” of how many times she’s been arrested. Since October, she had begun organizing weekly protests with the catchy nickname “Fire Drill Fridays.” She said she was inspired by activist Greta Thunberg, who every Friday since last year has been boycotting school to protest climate change.

Watch the full story on "Nightline" TONIGHT at 12:35 a.m. ET on ABC

“All of these young people striking on Friday, saying, ‘Come on, adults, where are you? We didn't cause this, but it's our future that's at stake. Don't let us fight for this by ourselves,’” Fonda said. “So I said, ‘Right, I'm not doing enough.’ … I want to be able to [put] my body on the line and kind of role-model what the next step should look like.”

Fonda acknowledges that climate activism can “seem overwhelming.”

“But here's the thing. In cities all over the country and states…they're all at the table figuring out what has to be done to reduce the carbon footprint of their particular city or state,” she said. “It's happening. It's just now it has to happen globally.”

Fonda believes that right now, “the most important thing is that all new fossil fuel expansion has to stop.”

“We can have windmills and solar panels and hydroelectric and all of those things. But if they keep drilling and keep emitting fossil fuel carbon dioxide, we're not gonna get there,” she said.

Prior to her workout empire, Fonda is perhaps best known for her on-screen roles in films like “Barbarella” and “Klute.”

But activism, like her Hollywood career, has been a lifelong journey for the star who’s been a regular at protests for years, and both revered and reviled for her efforts.

It all began in the 1960s, when Fonda took a stand against the Vietnam War. A trip to Hanoi landed the actress in hot water with veterans who believed the act was anti-American. That was just the beginning for Fonda.

In the decades since, she’s made her voice heard on arctic drilling, civil rights, reproductive rights, indigenous people’s rights, violence against women, the Iraq War and much more.

What’s different now, Fonda said, is the urgency of climate change.

“There's never been a ticking time bomb hanging over our heads. You know, this isn't one war or one issue in one place. This is the future of the entire planet,” Fonda said. “There's a looming catastrophe that will affect all of humanity. That's what's different. That's never happened before in the history of humankind.”

Fonda is making changes in her own life to combat climate change. She says the now-infamous red coat she wears to protests will be the last clothing purchase she’ll ever make.

“I had to get something red…it was on sale, and so I bought it,” she said. “I'm not ever buying anything new again. Of course, it's easy for me to say. I'm 82 and I don't have that much time to worry about it. It's becoming a thing, consumerism. And so, I thought, well, that's another way that I can try to be a role model.”

Fonda is serious about not buying new clothes, saying that the only exceptions would be underwear and socks.

In addition, she said, “I try to fly less… I’ve gotten rid of single-use plastics. I drive an electric car. I had a windmill and photovoltaic XLs on my roof since the ‘70s.”

Over the course of 13 weeks, Fonda has been joined on the steps of the Capitol by people like Taylor Schilling of “Orange is the New Black”; Ben Cohen and Jerry Greenfield, founders of Ben & Jerry’s ice cream; actor Ted Danson; and Lily Tomlin, Fonda’s “Grace and Frankie” co-star.

Fonda marched for her birthday, flanked by photographer Annie Lebovitz, activist Dolores Huerta and, of course, some serious Hollywood star power.

“There's so many fantastic people that are coming…to engage in civil disobedience with me. It moves me so much,” Fonda said. “I think that together we're gonna be braver and stronger to then go out each in our [own] way and step it up.”

Fonda’s longtime friend and fellow activist Sally Field also spoke to “Nightline” as she prepared for her first arrest.

“I'm here today because I know Jane is right. It's now we have to get loud. This is now… If you think climate change isn't happening, come live in California for a few months,” Field said. “The whole state is being systematically burned to the ground. It's terrifying… In the United States, there is not a region that is left untouched. It has to be done now. This is about me, maybe not so much. It's about my children and my grandchildren.”

Field said that at 73 years old, “it’s time to get arrested with Jane. I’m putting it on the line. I love this woman. I admire her so greatly.”

Later in the afternoon, true to her word, Field was led down the steps of the Capitol in zip ties. She had been arrested for civil disobedience, a misdemeanor.

“Most of the time, we're engaging in civil disobedience, which is a time-honored, noble thing to do,” Fonda said. “Martin Luther King helped changed civil rights laws, Gandhi freed India from British colonialism through civil disobedience and, you know, you get held for a little while. You pay $50 and you get let go. So it's kind of routine thing. But it does attract media attention.”

Fonda said she sees the arrests as a “transformative experience.”

“It's hard in life these days to be able to align your body with your deepest values,” she said. “That’s what happens when you engage in civil disobedience and risk getting arrested.”

With wildfires raging across Australia and the threat of other climate disasters looming, Fonda is buoyed by her faith and a hope that the world can change. She has “a lot” of faith that her activism will have an impact, she said.

“When you feel that you're part of a whole…I don't feel like just a little individual person. So it gives me a lot of strength. And I believe in the power of prayer,” Fonda said.

“Activism makes you hopeful. I was very depressed until I decided to come here and do this, because I knew I wasn't doing enough… The minute I came here and began to engage in activism with my whole body, I overcame the depression,” Fonda continued. “That's what activism can do. When you're doing something that you think can possibly make a difference in concert with other people, not as an individual but together with other people, it lifts despair.”