Veteran actor and activist has been arrested four times after being inspired by Greta Thunberg and disgusted by Trump

Jane Fonda has unusual plans for her 82nd birthday: she wants to spend the night in jail.

The American actor and political activist – who has been protesting about inaction over the climate crisis at the US Capitol every Friday – has been arrested four times and kept overnight once. Her lawyers have helped her avoid serious charges. But she says the acts of civil disobedience have pulled her out of a depression she sunk into after Donald Trump took office.

“With his election came a need to deeply study things that I didn’t understand enough, including why did he get elected,” Fonda said. “The answers to why he got elected began way, much earlier. And so that realisation has helped guide where I put my focus as an activist,” Fonda said in an interview with the Guardian.

Fonda – a huge star in the 1960s, 70s and 80s who has recently seen TV success in the hit Netflix show Grace and Frankie – knew Trump socially before he entered politics.

When he won the Republican nomination, she said she was relieved because she thought he would never win. And even if he did, she didn’t expect him to be ideological.

“I didn’t realise that he was a crook,” she said. “I did not realise the depth of corruption that exists in our government, and that kind of shocks me. I don’t like to think that this country is like, you know, the Latin American dictatorships, you know, Eastern European dictatorships, Russian dictatorships.”

Trump has belittled Fonda’s cause at recent campaign rallies, reminding his supporters that she was arrested decades ago when she was an outspoken critic of the Vietnam war. He also brought up Fonda’s 1972 visit to North Vietnam, which earned her the nickname “Hanoi Jane” and still taints her reputation, especially on the right.

Facebook Twitter Pinterest Jane Fonda with Donald Sutherland and other actors protesting against the Vietnam war. Photograph: Bettmann/Bettmann Archive

But Fonda is not just sparring with Republicans with her current campaign – she says Democrats, like the House leader, Nancy Pelosi, haven’t done enough on the climate crisis either, particularly to help people understand that fossil-fuel companies have known about the crisis and lied.

Fonda has supported women’s rights and opposed multiple wars over the past decades. Now she is proving an unlikely ally to the youth climate movement. Her protests aren’t huge, but they have drawn people around the country into activism and garnered plenty of media attention.

“I’m in my 80s, and I was literally thinking that I could perhaps learn new skills or do something I’d never done before. And when Trump was elected I realised I can’t, you know, it’s back to the barricades,” Fonda said.

She was inspired by 16-year-old Swedish climate activist Greta Thunberg, who she first read about in a book by Naomi Klein.

Because of her Asperger’s diagnosis, Greta is “unlike most of us, she’s not affected by compromise and you know, being popular or what other people might think”, Fonda said. “She can’t learn something horrific and then go about her business.”

Thunberg, who began a worldwide movement with her Friday strikes from school, fell into a deep depression over the environmental crisis when she was 11.

Fonda identifies with that despair.

“We’re holding grief in our bodies because we know 2.9 billion fewer birds exist in North America than in 1970, because we see pictures of polar bears starving, because we know that tens of millions of people are forced to leave where they live and forests are burning. We, unlike Greta, we go about our lives, but that’s lodged in our bodies. And I think it causes this existential angst,” she said.

Fonda still hasn’t met Greta. She wrote to her once, but someone else responded on Greta’s behalf.

The weekly Fonda protests – called Fire Drill Fridays – typically draw an older crowd, including some veterans. She is often flanked by celebrities – her Grace and Frankie co-star Sam Waterston, actor Ted Danson and the founders of Ben and Jerry’s ice cream have attended.

On the Thursdays before the protests, she features experts on Facebook Live to discuss detailed impacts of the climate crisis – including how it can exacerbate global unrest. She said she generally understood the problem but wanted to learn more about the specifics and who is to blame. Her plan is to help activate people who already care about climate change but don’t yet grasp its severity.

Fonda has been living in Washington DC to avoid the impact on the climate of flying back and forth from California. But she hasn’t been able to cancel all her travel.

Facebook Twitter Pinterest Abigail Disney, June Diane Raphael and Jane Fonda demonstrate outside the Russell US Senate office building during Fire Drill Friday in November. Photograph: John Lamparski/Getty Images

“We had to weigh, is it more important for me to be here, to carry out these actions in the long run, or to not fly,” she said. “We know that the fossil fuel executives, and the politicians that they’ve purchased, are flying all the time … And so it would put climate activists at a pretty big disadvantage if we didn’t fly.”

Fonda knows she isn’t the perfect climate advocate for every demographic. Asked if her activism could reach many working class Americans, she said: “No I think, unfortunately, because of the controversy of me in North Vietnam during the war I think that has made me anathema to a lot of those people.”

She acknowledges she’s not an expert in every part of climate science either. In a particularly adversarial interview with the BBC this week she was grilled on her sources for saying hundreds of millions of people could be displaced by the crisis. (She was correct, according to the World Bank, which said as many as 143 million people could be displaced by 2050.)

But she also was held to account in that interview for comparing fossil fuel companies to Nazis.

“Just like crimes against humanity have been put on trial at Nuremberg and elsewhere, the fossil fuel industry will hopefully be held accountable,’ she told Newsnight.

Fonda recognises that she and the protesters rallying with her are privileged and have it easy compared to many historical movements, but she said celebrities are an important tool for climate activism and shouldn’t be discounted.

“If I weren’t who I was, Fire Drill Fridays wouldn’t have taken off the way it did. It’s just that simple. I don’t ask to meet with the Senate task force on climate change. They ask to have me come. I have a platform. I have a hit series. And why not use it,” Fonda said.