Motor vehicles contribute to global warming by releasing greenhouse gases like carbon dioxide and chlorofluorocarbons. These emissions from highway vehicles worldwide make up about 4.7% of global warming. In the U.S., they account for around 2 to 2.5% of global greenhouse gases. The use of chlorofluorocarbons in cars plays a role too, representing 15% of global CFC-12 usage in 1985. To tackle this issue, the industry suggests phasing out CFCs if safe replacements are available and planning globally to reduce greenhouse gas emissions effectively. They also propose studying a carbon fee as a potential method to reduce carbon dioxide emissions from fossil fuels.