Greta Thunberg has questioned why some adults 'mock and threaten teenagers and children for promoting science'.
Sixteen-year-old Swedish climate activist Greta Thunberg has hit back at "the haters" who have criticised her impassioned speech at the United Nations.
The address has resulted in some backlash, including a dig from US President Donald Trump and some harsher words from conservative commentators.
But on Thursday, Ms Thunberg responded via Twitter.
"Here we go again ... the haters are as active as ever - going after me, my looks, my clothes, my behaviour and my differences. They come up with every thinkable lie and conspiracy theory," she posted.
"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.
"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."
Earlier this week, Fox News commentator Michael Knowles called her "a mentally ill Swedish child who is being exploited by her parents and by the international left".
The teen has previously described living with Asperger syndrome, which falls on the autism spectrum, as a gift because it helps her "see things from outside the box".
Mr Trump also appeared to mock Ms Thunberg, tweeting "she seems like a very happy young girl looking forward to a bright and wonderful future. So nice to see!"
And in Australia, One Nation leader Pauline Hanson said "I think that she's basically a teenager who has had no life experiences. She was actually voicing what other people have put into her head".
But many others have hailed Ms Thunberg's speech as a historic moment for the climate movement.
On Thursday, Man Booker Prize-winning Australian author Richard Flanagan said the address "may well prove to be the climate change movement's Gettysburg Address".
"Thunberg's speech, which took just four-and-a-half minutes to deliver, which, one suspects, will resonate long into the future," he wrote in the Guardian.
The teen scolded the audience at the UN Climate Action Summit on Monday, repeatedly asking, "how dare you?"
"I shouldn't be up here. I should be back at school on the other side of the ocean ... You come to us young people for hope. How dare you?" she said.
"We are in the beginning of mass extinction, and all you can talk about is the money and fairy tales of eternal economic growth. How dare you."