In this passionate call to action, 16-year-old climate activist Greta Thunberg explains why, in August 2018, she walked out of school and organized a strike to raise awareness of global warming, protesting outside the Swedish parliament and grabbing the world's attention. "The climate crisis has already been solved. We already have all the facts and solutions," Thunberg says. "All we have to do is to wake up and change." Presented at a TEDxStockholm event. (video: 11:12 min).