Greta Thunberg took a gap year from high school in 2019 to help spread awareness about climate change, and that journey is documented in her new string"Greta Thunberg: A Year to Change the World."

NEW YORK -- Greta Thunberg turned 18 in January, but she has already made peace with her future: While most college students will change their concentrations multiple times, the Swedish high school student says climate change activism is going to undoubtedly be her life's mission.

"In a perfect world, there would not have to be a climate activist, but unfortunately, there'll likely still be a need for climate activists for quite some time," she explained. "I believe I'll be doing this for so long as there's a demand for people to get this done."

The three-part show, a co-production between PBS and BBC Studios premiering Thursday on Earth Day, follows the then-16-year-old as she took a gap from school in 2019 to meet with scientists around the globe and spearhead awareness about climate change.

The docuseries reveals her visiting people and places that have been clearly influenced by the heating of the planet, such as Canada's Athabasca Glacier, a town in California burnt by wildfires and the indigenous Sami herders in Sweden where reindeer face starvation. She even sails throughout the North Atlantic throughout the ocean's busiest season to see how carbon dioxide emissions from ships have changed the chemistry of the ocean.

"A Year to Change the World" offers a look at her talking at enormous rallies, and also reveals how her momentum has been significantly slowed from the worldwide coronavirus pandemic. Thunberg, a 2020 Nobel Peace Prize nominee, said while she grew even more educated about climate change, there were moments that surprised her, like meeting Polish coal miners.

"I had expected them not to be happy to change, however they were eager to change. They desired to live in a more sustainable world... provided that they weren't left behind," said Thunberg. "I have met with world leaders that are less excited to modify."

And it's many of these heads of government who've positioned Greta as a political lighting pole and accidentally increased her worldwide profile. Brazil's conservative president Jair Bolsonaro has called her "brat," Russian President Vladimir Putin has stated she doesn't know that the"modern world is complex," and former president Donald Trump said her rallies, which resulted in cascades of boos. He famously tweeted,"Greta should work on her Anger Management problem, then go into some good old fashioned movie with a friend! Chill, Greta, Chill!"

Thunberg, the youngest person ever to receive Time's Person of the Year honor in 2019, said she doesn't fully understand why she is on the radar of government officials, however it shows that the message of climate change is reaching far and wide.

"When people like that do these kinds of things and say such things, of course, it is quite hilarious," said Thunberg. "it is a indication that we're doing something good, that we are having an impact, so that we take it as a compliment."

However, Thunberg says she believes what is most intriguing about the new job is exactly what the filmmakers weren't able to include.

"I think perhaps the most interesting thing about the documentary show is what didn't get into the series. I really don't know how many fashion companies like H&M, car companies like Volkswagen, oil companies such as Shell and airlines and so on that we asked for interviews, but they all refused consistently. And that, I think is quite interesting -- it says a good deal about them."

While U.S. PBS stations air the docuseries Thursday, Thunberg will likely be at her college in Sweden, which divides in-person courses to one day weekly. She'll also use Earth Day to testify almost to the U.S. Congress, along with scientists, about fossil fuel subsidies.

Thunberg says she understands that changing the world -- or perhaps getting her fellow global citizens to take care about how is it's changing -- doesn't occur immediately, but she needs everyone to know about how their daily actions can affect future generations.

"I'm not telling anyone to care," explained Thunberg. "But should you like yourself and your children and grandchildren to have the ability to live in a prosperous world and in a world where they can appreciate all of the things in life that you have gotten to appreciate, then you need to care. But naturally, that's up to you. I'm not telling you to do something -- rescuing the world is voluntary."