A 14-year-old climate activist inspired by Greta Thunberg sits outside the UN on Fridays. She says she's been getting death threats.

• Sixteen-year-old Swedish activist Greta Thunberg has encouraged students to skip school to demand action on climate change from their governments.
• One of her fellow activists, 14-year-old Alexandria Villaseñor, sits outside the United Nations headquarters in Manhattan on Fridays.
• Villaseñor said she has been harassed on social media and received death threats from climate deniers. But that has not stopped her.
• Visit Business Insider's homepage for more stories.

Almost a year ago, teen climate activist Greta Thunberg delivered an impassioned speech at the United Nations Climate Change Conference in Poland. Her remarks caught the attention of Alexandria Villaseñor, a New York middle-schooler who was 13 at the time.

Villaseñor had just visited family in northern California, and the trip coincided with the deadliest blaze in the state's history: the 2018 Camp Fire, which killed at least 85 people. She'd stayed in a town about two hours away from the flames, and said the smoke caused her asthma to flare up.

"I was sick," Villaseñor told Business Insider, adding that she donned a face mask and placed wet towels in the crevices of windows and doors at her family's home. "So I started to really research wildfires and I saw the connection between them and climate change."

When she came across a video of Thunberg's COP24 speech, Villaseñor said, she decided that she could help prevent a future climate-related disaster by joining Thunberg's Fridays for Future movement. The initiative encourages students to skip school to demand action on climate change from their governments, and it has swelled to encompass thousands of student activists like Villaseñor.

She now sits outside the United Nations headquarters in Manhattan on Fridays. Each time, Villaseñor brings a sign that reads "COP24 Failed Us," a reference to the fact that global emissions have continued to rise since that conference in December 2018. This week marked the one-year anniversary of her strike; she goes rain or shine and even sat outside the UN during a polar vertex.

"When Greta started striking, it gave permission to other students all around the world to go on protest as well," Villaseñor said. "She speaks with such authenticity that it really resonates with other young people."

But joining Thunberg's movement also comes with challenges: namely, criticism from adults. Villaseñor said she has been harassed on social media and even received death threats from climate-change deniers. But that hasn't stopped her from protesting.

Fridays at the United Nations

In December 2018, Villaseñor told her parents that she planned to skip seventh grade every Friday to go on strike.

"I had never gone to a protest before. I'd never been involved in any organizational space," she said. "At first it was like, is this really going to make a difference?"

Her parents gave their consent, she said, but her friends were confused.

"At first when I started striking, they didn't really understand why it was important or why I was doing it," she said. "It was my job to educate them."

By February, Villaseñor told the Washington Post that she was transferring to a private school that allows her take off for strikes, protests, and public appearances.

Teen climate strikers have catapulted to fame

Villaseñor is the first to admit that her life isn't that of a normal teenager. She has been photographed with Leonardo DiCaprio and she stood on stage next to Jane Fonda at Glamour's 2019 Women of the Year Awards.

On Wednesday, she gave a speech in front of Mark Ruffalo and former Vice President Al Gore at the TED World Theatre in New York City. Over the next few days, she'll be at COP25 in Madrid. Thunberg will be in Spain, too - she arrived in Lisbon via sailboat on Tuesday, since she refuses to fly because of airplanes' high greenhouse-gas emissions.

Villaseñor is less extreme than Thunberg when it comes to her efforts to reduce her own carbon footprint. She takes public transportation around New York, uses a bamboo toothbrush, and washes her hair with a bar of shampoo instead of shampoo from a bottle.

"I do look at my own habits," she said. "But the majority of our greenhouse gas emissions come from 100 companies all around the world."

For both of these young activists, and others like them, attracting international attention has been a key part of their strategy. But it has also landed the teens in stressful situations.

In September, President Donald Trump mocked Thunberg on Twitter after she shed tears during a speech at the UN General Assembly. Thunberg also said her sister, Beata, has experienced "systematic bullying, hatred, and harassment" online.

Villaseñor said she has been a topic of conversation on the right-wing news site Breitbart, where she received death threats in the comments section. The threats were so disturbing, she said, that Breitbart temporarily disabled its comments and purged some of the posts. But more vitriolic remarks sprung up after, Villaseñor added.

After receiving those threats, she said she felt the need to surround herself with more adults at protests.

"We make sure there are peacekeepers and marshals - people who can really watch the surroundings," she said.

But overall, Villaseñor added, the criticism motivates her.

"Whenever I see a climate denier or a troll, I find it a good sign," she said. "It just shows how threatened they are."

Villaseñor said she is motivated by anger

Villaseñor founded a group called Earth Uprising for young climate activists, and said the teens generally coordinate their efforts through social channels like WhatsApp, Instagram, and Slack. Facebook, she noted, is less common.

"I mean, what's Facebook?" she said teasingly. "I don't really use that one that much."

Villaseñor said she and her fellow activists communicated a lot about their excitement surrounding Thunberg's visit to New York in September.

"We were just ecstatic," she said. "It was amazing that she was coming here because she had inspired us in the first place to go out and take action."

But ecstasy is in rare supply during her protests and strikes. Instead, Villaseñor said, she's motivated by anger, grief, and frustration.

"Behind every protest there is a layer of anger," she said. "In the future, school won't matter anymore because we'll be too busy running from the next wildfire or hurricane."