The Global Warming Potential (GWP) of a gas is a measure of the degree, relative to carbon dioxide, to which the presence of that gas in the atmosphere will contribute to a long-term increase in global temperature. The calculation of the GWP for a given gas takes into account the efficiency of the gas in absorbing solar radiation (primarily determined by the infrared spectrum of the compound) and the time the compound will remain in the atmosphere before it is removed by natural processes. Thus, if a pulse of 1 kg of the gas is emitted to the atmosphere at the same time as a pulse of 1 kg of CO2, the GWP compares the warming effect of the gas relative to CO2 over various time horizons.
These two tables, derived from the 2021 and previous reports of the Intergovernmental Panel of Climate Change (IPCC) (Refs. 1-4), give the lifetime in years and the radiative efficiency for the major compounds identified in the Kyoto Protocol as contributing to global climate change. Column definitions for the tables are as follows.
Column heading | Definition |
Name | Compound chemical name or industrial designation of a greenhouse gas or normal air constituent |
Mol. form. | Molecular formula |
Lifetime | Lifetime of the compound, in years |
Radiative efficiency | A measure of the radiative forcing that influences the energy balance in the Earth–atmosphere system; in units of watts per square meter for a concentration of one part per billion (W m-2 ppb-1) (see Refs. 1-4); only in Table 1 |
GWP [20-yr est.] (year) | Global Warming Potential for a 20-year horizon; as estimated by the IPCC in the year specified within parentheses (Refs. 1-4) |
GWP [100-yr est.] (year) | Global Warming Potential for a 100-year horizon; as estimated by the IPCC in the year specified within parentheses (Refs. 1-4) |
GWP [500-yr est.] (year) | Global Warming Potential for a 500-year horizon; as estimated by the IPCC in the year specified within parentheses (Refs. 1-4) |
Table 1 summarizes the latest data from the 2021 IPCC report (see especially Ref. 3) for 68 important gases. Reference 3 also has similar data for many additional greenhouse gases. Table 2 provides a comparison of the 500-year estimates for 21 important greenhouse gases, most of which would have a significant impact on the global climate if their release is not controlled. Table 2 is included to show the consistency of the IPCC projections. The list of compounds includes those identified in the Montreal Protocol as contributing to ozone depletion, because these compounds also contribute to global warming. It also includes compounds used or proposed as replacements for the ozone-depleting compounds that still have global warming potential.
The calculation of a GWP involves a number of assumptions, and other measures have been proposed. See the references for detailed discussions.
Name | Mol. form. | Lifetime/years | Radiative efficiency/W m-2 ppb-1 | GWP [20-yr est.] (2021) | GWP [100-yr est.] (2021) | GWP [500-yr est.] (2021) |
Continued on next page... | ||||||
Natural Atmospheric Constituents | ||||||
Carbon dioxide | CO2 | 0.0000133 | 1 | 1 | 1 | |
Methane | CH4 | 11.8 | 0.000388 | 81.2 | 27.9 | 7.95 |
Nitrous oxide | N2O | 109 | 0.0032 | 273 | 273 | 130 |
Substances Controlled by the Montreal Protocol | ||||||
CFC-11 | CCl3F | 52 | 0.259 | 7430 | 5560 | 1870 |
CFC-12 | CF2Cl2 | 102 | 0.32 | 11400 | 11200 | 5100 |
CFC-13 | CF3Cl | 640 | 0.278 | 12400 | 16200 | 17500 |
CFC-113 | CFCl2CF2Cl | 93 | 0.301 | 6860 | 6520 | 2830 |
CFC-114 | C2Cl2F4 | 189 | 0.314 | 8260 | 9430 | 6150 |
CFC-115 | CF3CF2Cl | 540 | 0.246 | 7410 | 9600 | 9880 |
Halon-1301 | CF3Br | 72 | 0.299 | 8320 | 7200 | 2750 |
Halon-1211 | CF2BrCl | 16 | 0.3 | 4920 | 1930 | 552 |
Halon-2402 | CF2BrCF2Br | 28 | 0.312 | 4070 | 2170 | 639 |
Carbon tetrachloride | CCl4 | 32 | 0.166 | 3810 | 2200 | 658 |
Methyl bromide | CH3Br | 0.8 | 0.004 | 8.74 | 2.43 | 0.692 |
Methyl chloroform | CH3CCl3 | 5 | 0.065 | 567 | 161 | 46 |
HCFC-22 | CHClF2 | 11.9 | 0.214 | 5690 | 1960 | 560 |
HCFC-123 | CHCl2CF3 | 1.3 | 0.16 | 325 | 90.4 | 25.8 |
HCFC-124 | CHClFCF3 | 5.9 | 0.207 | 2070 | 597 | 170 |
HCFC-141b | CH3CCl2F | 9.4 | 0.161 | 2170 | 860 | 246 |