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Greenhouse Gases & Global Warming Potential

Updated:

May 28, 2024

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Overview

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

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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.

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

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‍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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