Cows and other grass-eating animals produce methane when they fart. In fact, they produce millions of tons of it each year. This gas can affect the climate. With this knowledge, some scientists wondered about dinosaurs. Logically, since some dinosaurs ate grass, then they may have produced methane as well. Doing the math, they concluded that yes, dinosaur gas had the possibility of affecting the climate.
Besides current animals, scientists also have a theory about how these herbivore dinosaurs process food. They noticed that the small teeth would make eating difficult. Instead, they figured that something in their stomach had to help break down the food. In 2012, they thought it might be microorganisms. This breakdown would produce methane gas that could have affected the environment.