CO2e (carbon dioxide equivalent) and GWP (global warming potential) work together to compare the heating properties of different greenhouse gases. Each gas stays in the atmosphere for different amounts of time, complicating the comparisons, but CO2e and GWP are how scientists measure them on a common basis.
Take methane and NO2 for example. Methane will trap 29.8 times more heat in the atmosphere on average than CO2 over 100 years, and NO2 will trap 273 times more heat on average than CO2 over 100 years. NO2 traps almost ten times the amount of heat that methane does. 1 ton of methane is equivalent to 29.8 tons of CO2, etc.
The table below shows the greenhouse gases officially controlled under the Kyoto Protocol and their GWP. Bear in mind that the natural sources of these gases are part of cycles which have stayed in relative balance for hundreds of millions of years. Human sources of these gases are the main drivers of the changes to our climate which, if unchecked, threaten to undermine our entire civilization.
| Greenhouse Gas | Natural Sources | Human Sources | Global Warming Potential (GWP) |
|---|---|---|---|
| Carbon Dioxide (CO2) | Animal respiration Decomposition of organic matter Forest fires Volcanic eruptions | Fossil fuels (power generation, transportation, industry) | 1 |
| Methane (CH4) | Wetlands Frozen undersea deposits (evaporation accelerated by ocean warming) Natural animal populations | Agriculture Fossil fuel burning/transportation Human waste Landfills Biofuels Biomass burning | 29.8 |
| Nitrous Oxide(N2O) | Bacterial decomposition in soils and oceans | Agriculture (manure and fertilizer) Fossil fuel combustion Industrial chemical production Wastewater treatment | 273 |
| Hydrofluorocarbons (HFCs) | None | Refrigerants Aerosol propellants Solvents Fire retardants | 5 – 14,600 |
| Perfluorocarbons (PFCs) | None | Aluminum production Semiconductor manufacturing | 78 – 12,400 |
| Sulfur hexafluoride (SF6) | None | Semiconductor manufacturing Natural gas leak detection Magnesium processing Electrical transmission insulation | 25,200 |
| Nitrogen trifluoride (NF3)3 | None | Semiconductor and microelectronics manufacturing | 17,400 |