In an angry and emotional speech at the United Nations climate summit on Monday, Swedish teenage climate activist Greta Thunberg tore into world leaders for failing to act.

"This is all wrong," Thunberg said, reading from a piece of paper. "I shouldn't be up here. I should be back in school on the other side of the ocean, yet you come to us young people for hope. How dare you."

"People are suffering," the 16-year-old continued through tears. "People are dying. Entire ecosystems are collapsing. We are at the beginning of a mass extinction and all you can talk about is money and fairy tales of eternal economic growth. How dare you."

"How dare you continue to look away and come here saying you are doing enough," Thunberg added. "You say you hear us and understand the urgency, but no matter how sad and angry I am, I do not want to believe that. Because if you really understood the situation and still kept on failing to act, then you would be evil. And that I refuse to believe."

Teenage climate activist Greta Thunberg speaks during the U.N. Climate Action Summit in New York on Monday. (Timothy A. Clary/AFP/Getty Images)

Thunberg was on a panel with other climate activists at the summit on the eve of the U.N. General Assembly to encourage countries to meet the goals of the Paris Agreement and reduce greenhouse gas emissions by 2020.

She was among 16 children to file a legal complaint with the United Nations Monday, accusing five countries — France, Germany, Brazil, Argentina and Turkey — of not doing enough to combat climate change.

[Greta Thunberg overshadows Trump at U.N. General Assembly]

President Trump, whose administration have been widely criticized for rolling back environmental protections and withdrawing from the Paris climate accord, was not scheduled to attend the event. But he did, later, after Thunberg had concluded her remarks. (He left after about 10 minutes.)

Thunberg, though, did see Trump in the hallway.

Last week, Thunberg testified on Capitol Hill, urging lawmakers to "listen to the scientists" who say climate change is real and that humans are responsible — conclusions that Trump has resisted.

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“I want you to unite behind science,” Thunberg said in her testimony before the House Select Committee on the Climate Crisis on Wednesday. “I want you to unite behind science. And then I want you to take action.”

Thunberg submitted to Congress a 2018 report on global warming by the Intergovernmental Panel on Climate Change, which warned about the impacts of global warming of 1.5°C that researchers say is likely between 2030 and 2052 if it continues at the current rate.

“This is not political views or my opinions,” she said. “This is science.”

Thunberg, who has been nominated for a Nobel Prize for her work raising awareness about climate change, has become an inspirational figure for fellow teens. Last month, she sailed from Europe to the United States on a zero-emission yacht.

She also met with former President Barack Obama, who praised her for her work.

"You're changing the world, so we're very excited to have you," he said.

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