Climate change activist Greta Thunberg is angry, and it's not just about climate change.

Thunberg is standing up to the haters, telling millions of her supporters not to waste time "giving them any more attention."

The Swedish 16-year-old climate activist recently gave an impassionate speech at the United Nations Climate Action Summit in New York.

Addressing a room full of world delegates, she expressed her disappointment with world leaders:

"The young people are starting to understand your betrayal. The eyes of all future generations are upon you. And if you choose to fail us, I say, we will never forgive you."

It seems her words fell on some deaf ears as many have criticized her passionate, tearful speech.

Following her speech, some social media users attacked Thunberg's manner, appearance, and autism. Thunberg shared her thoughts, asking why her critics were 'coming for her' when she's just trying to help the world.

Taking to Twitter, Thunberg, who was nominated for the 2019 Nobel Peace prize back in March, slammed her critics in a blistering thread.

She wrote:

"As you may have noticed, the haters are as active as ever - going after me, my looks, my clothes, my behavior, and my differences. They come up with every thinkable lie and conspiracy theory."

"It seems they will cross every possible line to avert the focus since they are so desperate not to talk about the climate and ecological crisis."

She also emphasized that "being different is not an illness," likely referencing the Fox News right-wing commentator who dubbed her a "mentally ill Swedish child."

She continued:

"Being different is not an illness, and the current, best available science is not opinions - it's facts."

She expressed her confusion, wondering why grown-up adults would verbally attacking her instead of offering ideas to solve climate change problems.

Thunberg remarked:

"I honestly don't understand why adults would choose to spend their time mocking and threatening teenagers and children for promoting science when they could do something good instead. I guess they must simply feel so threatened by us."

Concluding the Twitter thread, Thunberg encourages climate change supporters not to be swayed by critics.

She said:

"But don't waste your time giving them any more attention. The world is waking up. Change is coming (whether) they like it or not."

Thunberg had been leading youth climate strikes and even founded "Fridays for Future," a global movement that encourages students to walk out of their classrooms against inaction toward climate change.