Thunberg spoke Friday in Denver, where she said she was overwhelmed by a crowd of several thousand people at a climate strike rally. She said those supporting the cause represent "real hope." In contrast, she again scolded leaders for not doing enough and ignoring science. Echoing a line from a speech she delivered at the United Nations last month, she asked several times of leaders, "How dare they?" Some in the Denver crowd repeated the line.
Thunberg took the stage for less than 10 minutes toward the end of an event that highlighted young activists.
Swedish climate activist Greta Thunberg plans to join a climate strike in Denver on Friday.
The event near the Colorado state Capitol will include a panel of youth activists and end with a "die-in" that organizers say will symbolize those people facing danger and death because of climate change.
Thunberg has staged weekly "Fridays for Future" demonstrations for a year to call for faster action against climate change. She has inspired students around the world to skip classes on Fridays to demonstrate as well.
The 16-year-old sailed to the U.S. in August to promote her climate change campaign. She garnered international attention when she scolded world leaders at the United Nations.
She's touring the Americas for several months, concluding with a U.N. climate conference in Chile in December.