All Greenhouse Gases Aren’t Alike

The principal greenhouse gases include carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N2O), and the chlorofluorcarbons (CFCs).  They vary according to how much warming each can cause relative to CO₂ (set at 1).  This is called their Global Warming Potential or GWP.  They also vary by how long they stay in the atmosphere.  

The table on the right shows the principal greenhouse gases, the length of time each remains in atmosphere, their global warming potential relative to carbon dioxide, and their primary current sources.  Data from EPA.

Click on figure to enlarge.

Carbon Dioxide Equivalent (CO₂e)

Since all greenhouse gases do not have the same global warming potential, to compare them one to another on a par relative to the warming they cause, all greenhouse gases are assigned a carbon dioxide equivalent number (CO₂e).  For example, the carbon dioxide equivalent for methane is approximately 21 times that of carbon dioxide, nitrous oxide is about 319 times that of carbon dioxide, and so on.