(CNN) Teen activist Greta Thunberg on Friday again criticized world leaders gathered for the COP25 conference in Madrid for not doing enough to stop the ecological crisis that's damaging the planet.

"We have been striking for over a year, and basically nothing has happened," she told activists at the talks. "The climate crisis is still being ignored by those in power, and we cannot go on like this."

The sort of global children's protests Thunberg has inspired and led in recent months are "not sustainable," the 16-year-old continued.

"We cannot go on like that," Thunberg said. "We would love some action from the people in power. ... People are suffering and dying from the climate ecological emergency, and we cannot wait any longer."

Thunberg criticized world leaders for not doing enough to stop the climate crisis.

She warned that "it is impossible for anyone to know how the world will look in 10 years" and said she hopes the summit will lead to "concrete" change.

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