Combustion of fossil fuels not only emits carbon dioxide into the air, it also releases other gases like carbon monoxide, methane, nitrous oxide, etc. that cause air pollution. When in air, these gases dissolve in water (in the form of clouds) and convert into harmful acids like sulfuric acid and carbonic acid. These chemicals return to the surface of the earth in the form of acid rain, which has a huge impact on the entire environmental conditions. It harms the plants, soil and pollutes water.