People participate in a strike to call attention to climate change in Chicago, the United States, on Sept. 20, 2019. (Photos: Xinhua)

People participate in a strike to call attention to climate change in Chicago, the United States, on Sept. 20, 2019.

People participate in a strike to call attention to climate change in Chicago, the United States, on Sept. 20, 2019.

A cardboard with slogans is seen in a strike to call attention to climate change in Chicago, the United States, on Sept. 20, 2019.

People participate in a strike to call attention to climate change in Chicago, the United States, on Sept. 20, 2019.

People participate in a strike to call attention to climate change in Chicago, the United States, on Sept. 20, 2019.

People participate in a strike to call attention to climate change in Chicago, the United States, on Sept. 20, 2019.

People participate in a strike to call attention to climate change in Chicago, the United States, on Sept. 20, 2019.

People participate in a strike to call attention to climate change in Chicago, the United States, on Sept. 20, 2019.

A young man participates in a strike to call attention to climate change in Chicago, the United States, on Sept. 20, 2019.