Greta Thunberg joined a large crowd of young people skipping school in Iowa City, Iowa for a climate change protest on Friday, where she declared the recent United Nation’s action summit on climate change a flop.

The summit, which ran in conjunction with the U.N.’s annual General Assembly meeting, featured Thunberg and other youth speakers.

“We told world leaders to act on the science,” Thunberg, 16, said at the protest inspired by the Fridays for Future school walkout she started a little over a year ago in her homeland Sweden. “And we demanded a safe future for us and for everyone.”

“But they didn’t listen,” Thunberg said. “As we all know, the U.N. climate action summit was a failure.”

“That was, unfortunately, what we had expected,” Thunberg said.

Thunberg said world leaders are “uncomfortable” standing behind the “science.”

Thunberg opened her remarks at the event, where one speaker said that ending climate change would require “entire societal upheaval,” by stating that the protest was taking place on “indigenous Iowa land.”

She said that some seven million people in 180 countries joined the recent “global climate strike.”

“That is something that you can’t continue to ignore,” Thunberg said.

She told the crowd that giving up on their fight “is simply not an option” and chided world leaders for “acting like children.”

“Someone needs to be the adult in the room,” Thunberg said.

She said the protests will probably continue for “years,” despite the fact that Thunberg and other climate change activists, including many in the United States Congress, have said only 11 years remain before irreversible catastrophe.

Thunberg gained international attention in August when she traveled from Europe to New York City on a racing yacht to avoid making a “carbon footprint” by flying across the Atlantic.

Critics pointed out that the boat’s crew flying back and forth made an even larger carbon footprint and that the boat itself was made from fossil fuel-based products.

It’s not clear how Thunberg, who is taking months off from school to protest climate change in North and South America, got to Iowa. It is known that, after the failed U.N. event, she traveled to Canada for a protest in an electric vehicle owned by former actor and California governor Arnold Schwarzenegger.

Thunberg told the crowd that if adults didn’t do something to end climate change, young people would.

“Change is coming whether they like it or not,” Thunberg said.

Follow Penny Starr on Twitter @PennyStarrDC