Greta Thunberg on Her Fight to Save the Planet — and Why Asperger's Is Her 'Superpower'

The planet is in trouble — and teenage climate activist Greta Thunberg wants to make sure we do something about it before it’s too late.

“I think most people are still very unaware of how big this crisis is,” Thunberg, 16, tells PEOPLE.

Named one of PEOPLE’s 25 Women Changing the World for 2019, the Swedish student has been nominated for the Nobel Peace Prize for all she has done to raise awareness about the need to curb carbon emissions to prevent the most catastrophic effects of an overheating planet.

“There are already countless people suffering today from the climate,” she says.

If the world doesn’t do enough to lower global temperatures, then climate change-induced flooding, drought, monster hurricanes, and raging wildfires “will only get worse,” she says.

“There is no second option.”

RELATED: Teen Climate Activist Greta Thunberg Blasts World Leaders at the U.N. — ‘How Dare You!’

Now a powerhouse in the climate change world with millions of followers, Thunberg began her journey solo.

Concerned that her government wasn’t doing enough to curb carbon emissions, Thunberg, then 15, skipped school on Aug. 20, 2018, and sat alone outside of Swedish Parliament to protest climate inaction.

For much more on PEOPLE’s Women Changing the World 2019, pick up this week’s issue of PEOPLE, on newsstands Friday

The idea caught on and now millions of kids and teens worldwide hold their own “Fridays for Future” school strikes for climate inaction, just like Thunberg did.

“Right now, I have a lot of people listening to what I am saying, so I am using that platform to try to achieve a change.”

She still finds it hard to believe that her protests exploded into a massive worldwide movement.

“I could never have predicted this,” she says. “I don’t think anyone could have.

Now she is a global force.

In August, she sailed across the Atlantic in a carbon-neutral boat to speak at the U.N. Climate Action Summit on Sept. 23, where she urged world leaders and delegates in an impassioned speech to step up and take immediate action to prevent the most catastrophic effects of an overheating planet in coming years.

Three days earlier, she inspired an estimated 6 million people in more than 150 countries to take to the streets in the biggest climate march in history.

RELATED: Kids Suing the U.S. Government to Take Action Against Climate Change: It’s a ‘911’ Situation

Not surprisingly, her forceful message has drawn critics.

“Some have said that people should not listen to me because I don’t know what I’m saying or because I am mentally disturbed, and so on,” she says. “It’s just hilarious because they are desperate to find anything to complain about.”

By the way, she adds, she could care less. “I always ignore those people,” she says. “They don’t deserve my attention.”

Just as she embraces her critics, she celebrates her Asperger’s – a form of autism she calls her “superpower.”

“Being different is a good thing,” she says. “It’s something we should aspire to be.”

For now, she will continue fighting.

“Even though some scientists say that we have already passed the tipping point, you cannot think like that,” she says.

“You cannot think that we are doomed. We are not doomed unless we choose to be, unless we want to be. My hope is that we can fix it in time.”