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: epa.gov).
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 (epa.gov)
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.