Carbon Accounting Essentials
GHG Protocol Fundamentals

Greenhouse Gases & Global Warming Potential

May 28, 2024
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Greenhouse Gasses

Now, let's talk about how GHG emissions are calculated. We'll start with greenhouse gasses.

A greenhouse gas (GHG) is any gas that traps heat in the atmosphere. The GHG Protocol covers the accounting and reporting of the seven greenhouse gasses covered by the UNFCCC and Kyoto Protocol.

The table below provides information about the seven GHGs and their sources:

GHG Formula Common Sources
Carbon Dioxide CO2 Energy generation and Manufacturing
Methane CH4 Energy generation, Livestock, and Oil & Gas Production
Nitrous Oxide N2O Energy Generation and Fertilizer
Hydroflourocarbons HFCs Refrigeration, Building Insulation, Fire Extinguishing, and Aerosols
Perflourocarbons PFCs Manufacturing (Cleaning) and Apparel/Footwear (Waterproofing)
Sulfur Hexafluoride SF6 Power Lines and Radiology
Nitrogen Trifluoride NF3 Electronics and Lasers

Every GHG inventory will have at least carbon dioxide, methane, and nitrous oxide emissions because these are products of combustion, and every organization uses some form of energy.

Other gasses will vary in their presence and prevalence across industries and sectors.


Global Warming Potential

Greenhouse gasses are not all equal in their ability to warm the planet.

Each greenhouse gas varies in its ability to trap heat — making some GHGs more potent in their ability to warm the environment than others.

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To consistently measure and compare these gasses, the heat-trapping potential of each gas must be converted into a common unit. That conversion is done using global warming potentials.

Global Warming Potential (GWP)

A GWP is a factor indicating the relative heat-trapping ability of one unit of a given greenhouse gas — compared to one unit of carbon dioxide.

The table below lists the global warming potentials of each GHG. Because carbon dioxide is used as a benchmark to the other gasses, its GWP value is 1.

Greenhouse Gas Formula Example GWP (AR4)
Carbon Dioxide CO2 1
Methane CH4 24
Nitrous Oxide N2O 298
Hydrofluorocarbons HFCs 124-14,800
Perfluorocarbons PFCs 7,390-17,700
Nitrogen Trifluoride NF3 17,200
Sulfur Hexafluoride SF6 22,800


The GHG Protocol requires all greenhouse gas emissions be reported in units of carbon dioxide equivalent, or CO2e.  To complete this conversion, a GWP value (provided by the IPCC) is applied to the GHG. The GHG Protocol stipulates that GWP factors must be based on a 100-year time frame.

Let's look at an example.

In the table below, we have 10 kg of each greenhouse gas. Notice how the final outputs of CO2e emissions vary widely — even though we start with equal amounts of each GHG.

This illustrates how some gasses are far more potent than others.

Greenhouse Gas Emissions (kg GHG) Example GWP (AR4) GHG Emissions (kg CO2e)
Carbon Dioxide 10 x 1 = 10
Methane 10 x 24 = 240
Nitrous Oxide 10 x 298 = 2,980
Hydrofluorocarbons 10 x 124 - 14,800 = 1,240 - 148,000
Perfluorocarbons 10 x 7,390 - 17,700 = 73,900 - 177,000
Nitrogen Trifluoride 10 x 17,200 = 172,000
Sulfur Hexafluoride 10 x 22,800 = 228,000

10 kg of CO2 converts to 10 kg CO2e.

10 kg of SF6 converts to 228,000 kg CO2e.

By using GWP values, we can see that sulfur hexafluoride is 22,800 times more detrimental to the environment than carbon dioxide.

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