Emissions (million me carbon dioxide equ ☐ ☐ ☐ ם 4,000 2,000 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 Carbon dioxide Methane Ye Other greenhouse gases 2008 2010 2012 Fluorinated gases Source: U.S. EPA's Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2013. http://www.epa.gov/climatechange/ghgemissions/usinventoryreport.html What percentage of total greenhouse gas emissions is caused by natural sources? Should industries emitting carbon dioxide in huge amounts be fined or punished? Why are carbon dioxide emissions so much higher than other greenhouse gases? Why did the quantity of carbon dioxide emissions stay constant throughout the period? What is the chemical formula for methane? ​