IOWA CITY, Iowa (AP) — Thousands of people crowded the streets of downtown Iowa City on Friday to demand action on climate change and welcome 16-year-old Swedish climate activist Greta Thunberg.

Thunberg told the crowds she was stunned by the number of people who had turned out, telling them, “This is the real hope — so many people gathering here on a weekday with such short notice.”

The teen reiterated the message she has spread around the world to act on science in addressing climate change. Thunberg spoke to world leaders last month at a United Nations summit in New York and has led students in global protests demanding action on climate change.

In Iowa City on Friday, she drew cheers when she said teens and children should have to take on such responsibility, “but right now, the world leaders keep acting like children, and somebody needs to be the adult in the room.”