As fashion buyers and media squeezed into their seats alongside a catwalk at January's Pitti Bimbo — the semiannual children's wear trade show extravaganza in Florence — a recording of climate change activist Greta Thunberg's fiery United Nations speech played on a loop. "This is all wrong. I shouldn't be up here," her voice thundered. "How dare you?"

It was an apt question, considering the purpose of the three-day affair, including the “Children’s Fashion From Spain” show about to start that morning: to sell new kid styles for the upcoming fall-winter season.

Thunberg, the 17-year-old Swede and youngest Time Person of the Year, is an avowed proponent of “shop stop,” the idea that you never buy any clothing you don’t absolutely need, and proudly dresses in a secondhand wardrobe.

The cognitive dissonance continued as munchkin models stomped up and down the runway while toting pithy posters. (Sample slogans: “Cool kids saving a hot planet” and “There is no planet B.”) The vibe was very “global climate strike,” and some eco-fabrics were on display, although many of the looks — such as a short, poofy white party dress — would be impractical in such a setting. It ended in a shower of green confetti.

There’s no doubt that the event was on trend. In the coming weeks, references to our pending environmental apocalypse and upcycled clothes would be featured in women’s ready-to-wear shows in New York, Milan and London. But while there was variation on the theme on the grown-up runways, Pitti Bimbo felt more like a gushing Greta fan letter.

In February, Thunberg took to Instagram to complain that “my name and the #FridaysForFuture movement are constantly being used for commercial purposes without any consent whatsoever.” She went on to explain that she was applying to trademark her name, Fridays for Future and Skolstrejk för klimatet. (When I reached out to Thunberg for comment on this story, I was told she is not giving interviews at the moment.)

Whether she likes it or not, though, Thunberg, known for wearing a yellow raincoat and plaid button-down shirts, is now a fashion icon. In a September blog post for a brand called Töastie, company founder Kirstie Duke wrote admiringly of the teenager, “Her words hit hard,” then went on to detail the brand’s commitment to becoming more sustainable.

At the top of the post is a photo of Thunberg, the hood up on her trademark slicker. Below are several shots of kids playing in a similar Töastie jacket (about $92), one bearing the caption “Mini Gretas.” The coordination wasn’t planned ahead of time, promises Duke, who explains that a social media influencer who frequently snaps pics of her family frolicking in nature had asked for a pair of coats. “We were struck by the images,” she says. “For us, Greta is an inspiration, not a marketing tool.”

The fact that Greta is now considered a muse is important, says Marianna Sachse, founder of Jackalo, a brand that specializes in sustainable pants and coveralls. She chooses materials and manufacturing processes that aim to minimize waste and pollution, and she even created a program to buy back Jackalo pieces from customers, so the clothes can be resold or recycled.

“You have to meet people where they are, and the fashion industry is just waking up. The first step is awareness,” notes Sachse. Jackalo, for instance, had a booth in the “Ecoethic” area of the Pitti Bimbo trade show dedicated to planet-friendly brands, as did Töastie. Walking along the booths, I saw raincoats made from plastic bottles, recycled cashmere sweaters, and a whole lot of gender-neutral tops and bottoms designed to live on as hand-me-downs.

There are also skeptics such as Elizabeth L. Cline, author of “The Conscious Closet: The Revolutionary Guide to Looking Good While Doing Good,” who notes, “We’re not going to shop our way out of climate change.” Cline isn’t opposed to buying new clothes, especially when they’re responsibly made, versatile pieces made to hang on to for a while. But she’s not comfortable with the way brands are co-opting Thunberg’s face and words. “It’s enough to give you whiplash to see how quickly fashion commodifies any political movement,” she says.

Cline reserves her greatest scorn for Thunberg-themed
T-shirts, which have proliferated in the past year — both for kids and adults. Tees take an outsize toll on the environment because they’re so likely to be tossed, she says.

For kids who want to be like Thunberg, Cline advises, borrow and swap clothes as much as possible. And when you want to make a statement, do it by showing up at a protest. She says, “Your mere presence will indicate which side you’re on.”

Vicky Hallett is a former Washington Post columnist.