gwp carbon dioxide emissions epa footprint

What is GWP (Global Warming Potential)?

Global-warming potential (GWP) is the amount of heat a greenhouse gases maintains in the Earth’s atmosphere. All greenhouse gases have GWP, which then explains the impact greenhouse gases have on global warming. Each gas’ heat-absorbing ability (GWP rate) is usually compared to that of carbon dioxide (CO2).

For example, methane is a major contributor to the greenhouse effect. Methane’s GWP is 21. So methane is about 21 times more heat-absorptive than carbon dioxide and can remain in the atmosphere for 12 years. Nitrous Oxide (N2O) has a GWP of approximately 310. This means one pound of Nitrous Oxide can warm the atmosphere over 300 times more than a pound of Carbon Dioxide. In 2012, Nitrous Oxide accounted for about 6% of all US greenhouse gas emissions from human activities (source:

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Sources of Greenhouse Gas Emissions

There are four main greenhouse gases: Methane, Nitrous Oxide, Flourinated Gases and Carbon Dioxide. How do these gases get into the atmosphere? Here’s an visual of the greenhouse gas emissioins just for the United States (

Each type of greenhouse gas has a GWP. The higher the GWP, the higher the impact it has on global warming.

What does GWP have to do with your Carbon Footprint? If you take the total emissions of a given human act, such as driving a car or running your air conditioning, you can estimate a number of total greenhouse gas emissions that occurred over a time period. This total number is your carbon footprint.