Teenage climate activist Greta Thunberg has hit back at adults who “choose to spend their time mocking and threatening teenagers and children for promoting science”, suggesting they “must simply feel so threatened”.

The 16-year-old gave a furious speech at the United Nations General Assembly on Monday, viewed millions of times around the world and described by one commentator as “the climate change movement’s Gettysburg Address”.

But it sparked criticism and jibes from some pundits and politicians – including US president Donald Trump – some of whom attacked her manner, appearance and autism.

After changing her Twitter bio to quote Mr Trump’s taunt that she seemed like a “very happy young girl looking forward to a bright and wonderful future”, Ms Thunberg implored her followers not to waste their time giving more attention to critics “desperate” to avert the focus from climate change.

“As you may have noticed, the haters are as active as ever – going after me, my looks, my clothes, my behaviour and my differences,” she wrote on Wednesday. “They come up with every thinkable lie and conspiracy theory.

Greta Thunberg inspires climate activists everywhere: In pictures Show all 12 1 /12 Greta Thunberg inspires climate activists everywhere: In pictures Greta Thunberg inspires climate activists everywhere: In pictures In the protest that started a movement, Greta skips school to sit outside of the Swedish parliament in Stockholm in order to raise awareness of climate change on 28 August 2018 Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta speaks at the World Economic Forum in Davos on 25 January AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta stages a protest at the World Economic Forum in Davos on 25 January Reuters Greta Thunberg inspires climate activists everywhere: In pictures Greta speaks at the House of Commons in London on 23 April PA Greta Thunberg inspires climate activists everywhere: In pictures Greta addresses to the occupation at Marble Arch in London on 21 April AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta meets the pope on a visit to Rome Reuters Greta Thunberg inspires climate activists everywhere: In pictures Greta speaks at the senate in Rome on 18 April Reuters Greta Thunberg inspires climate activists everywhere: In pictures Greta addresses a debate of the EU Environment, Public Health and Food Safety committee at the European Parliament in Strasbourg on 16 April AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta receives the Special Climate Protection Award at the German Film and Television awards in Berlin on 30 March AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta attends a children's climate protest in Berlin on 29 March AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta addresses a children's climate protest on 1 March in Hamburg Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta attends a meeting for the Civil Society For rEUnaissance at the EU Charlemagne Building in Brussels on 21 February AFP/Getty

“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. Being different is not an illness and the current, best available science is not opinions – it’s facts.

“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.

“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.

“See you in the streets this Friday.”

Ms Thunberg rose to prominence after her solitary protests outside the Swedish parliament grew into a global movement of school strikes.

Demonstrations inspired by Ms Thunberg, along with those organised by Extinction Rebellion, have helped propel the issue to the top of the global agenda and forced governments to pledge more urgent action on climate change.

“You have stolen my dreams and my childhood with your empty words,” she quietly thundered to UN delegates on Monday, shaking with emotion. “We are in the beginning of a mass extinction and all you can talk about is money and fairytales of economic growth. How dare you?”

Greta Thunberg tells world leaders: 'You have stolen my dreams and my childhood with your empty words'

On Tuesday, Fox News apologised after a pundit said that if the climate movement “were about science, it would be led by scientists rather than by politicians and a mentally-ill Swedish child who is being exploited by her parents and by the international left.”

The comment came hours after host Laura Ingraham likened Ms Thunberg to a Stephen King-based horror film about a group of children who form a murderous cult after being manipulated by a supernatural force.

Ms Ingraham’s brother condemned his “sibling who I no longer recognise”, saying: “Clearly my sister’s paycheck is more important than the world her three adopted kids will inherit.”

On Wednesday, the teenager was awarded Sweden’s alternative Nobel Prize, the Right Livelihood Award for her activism.

The award was shared with Brazilian indigenous leader Davi Kopenawa, for her efforts to protect the Amazon rainforest, Guo Jianmei, a Chinese women’s rights lawyer and Aminatou Haidar, a Western Sahara human rights defender.

Ms Thunberg has also been nominated for a Nobel Peace Prize, the winner of which will be announced in the first week of October.