Key moment: Since the early 1970s, activists have called attention to the issue of climate change. On Sept. 21, 2014, people from more than 150 countries participated in the People’s Climate March to demand action on the global climate crisis.
Historical significance: Young people have been at the forefront of climate activism, and the 2014 march was a large-scale event that drew global attention to the issue. Studies show climate change disproportionately burdens children and young people. (Photo by Alejandro Alvarez/Creative Commons)