text: Cars produce up to 12% of Europe's greenhouse gases and up too 50% of America's greenhouse gas. High levels of greenhouse gas absorb heat and prevent it from leaving Earth's atmosphere causing a rise in temperature better known as global warming. Second, the carbon monoxide and other noxious chemicals that are released by vehicles can come together to form a thick smog. This somg is very bad for people's health and can contaminate land and water with toxic chemicals. In order to prevent these two things a lack of usage of cars is necesary in today's world.