Young Swedish activist Greta Tonberg, with her weekly campaign on climate change, moved to the United Nations yesterday and urged "anyone who cares about the future" to join her when world leaders meet in New York next month.

Tonberg, 16, began to miss school on Fridays a year ago to protest outside the Swedish parliament, leading to the formation of a global climate movement known as "Fridays for the Future." She was joined by 14-year-old Alexandria Villasenor, a New York resident who began a sit-in outside the United Nations in New York last December.

The activists, some 200 other young protesters, backed placards reading "Help me, my house is burning." "If you don't act like adults, we will," and "Science is not silence." Their chants included "We cannot be stopped, a better world is possible", "Sea levels are rising and so are we."

Tonberg is scheduled to speak at the September 23 climate summit at the annual meeting of world leaders at the UN General Assembly. She arrived in New York on Wednesday in a carbonless boat, completing an almost 14-day trip from England.

When she arrived in New York, Tonberg said: "Anyone who cares about our future should join and strike on 20 and 27 September."

The Swedish activist met with President of the United Nations General Assembly Maria Fernanda Espinoza on Monday.

Tonberg plans to attend the 25th United Nations Climate Change Conference in Santiago, Chile, in December, and plans to make her way there without air travel. She took leave to study for a year to campaign for climate action in the Americas with plans to visit Mexico and Canada as well.