A lawsuit known as Juliana v. United States was brought by the nonprofit group Our Children’s Trust, and the plaintiffs are 21 youths, now between 11 and 22 years old. They accuse the US government of failing to tackle man-made changes to our atmosphere, thereby failing its duty in what is known as the “public trust doctrine”: a centuries-old principle that the government acts as a steward, or trustee, of natural resources and must protect them for use by future generations.