While cars have undoubted advantages, of which their convenience is the most apparent, cars also have many significant disadvantages. Almost all cars run either on petrol or diesel fuel, both of which are fossil fuels. Burning these fuels causes the car to emit serious pollutants, such as carbon dioxide, carbon monoxide, and nitrous oxide. Not only are these gases harmful for health, causing respiratory disease and other illnesses, they also contribute to global warming, an increasing problem in the modern world.