Flat Earthism and the idea that human activity is not responsible for climate change are two of the most prevalent conspiracy theories today. Both have been increasing in popularity since the late 20th century. Currently, 16% of the US population say they doubt the scientifically established shape of the Earth, while 40% think that human-induced climate change is a hoax. But proponents of one of these theories are not necessarily proponents of the other, even though both are often motivated by a common mistrust of authority. In fact, they regularly contradict one another.