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Comparison of global warming potential (GWP) of three greenhouse gases over a 100-year period: Perfluorotributylamine, nitrous oxide and methane, compared to carbon dioxide (the latter is the reference value, therefore it has a GWP of one)

Global warming potential (GWP) is an index to measure how much infrared thermal radiation a greenhouse gas would absorb over a given time frame after it has been added to the atmosphere (or emitted to the atmosphere). The GWP makes different greenhouse gases comparable with regard to their "effectiveness in causing radiative forcing".^[1]^: 2232 It is expressed as a multiple of the radiation that would be absorbed by the same mass of added carbon dioxide (CO₂), which is taken as a reference gas. Therefore, the GWP has a value of 1 for CO₂. For other gases it depends on how strongly the gas absorbs infrared thermal radiation, how quickly the gas leaves the atmosphere, and the time frame being considered.

For example, methane has a GWP over 20 years (GWP-20) of 81.2^[2] meaning that, for example, a leak of a tonne of methane is equivalent to emitting 81.2 tonnes of carbon dioxide measured over 20 years. As methane has a much shorter atmospheric lifetime than carbon dioxide, its GWP is much less over longer time periods, with a GWP-100 of 27.9 and a GWP-500 of 7.95.^[2]^: 7SM-24

The carbon dioxide equivalent (CO₂e or CO₂eq or CO₂-e or CO₂-eq) can be calculated from the GWP. For any gas, it is the mass of CO₂ that would warm the earth as much as the mass of that gas. Thus it provides a common scale for measuring the climate effects of different gases. It is calculated as GWP times mass of the other gas.

Definition

The global warming potential (GWP) is defined as an "index measuring the radiative forcing following an emission of a unit mass of a given substance, accumulated over a chosen time horizon, relative to that of the reference substance, carbon dioxide (CO₂). The GWP thus represents the combined effect of the differing times these substances remain in the atmosphere and their effectiveness in causing radiative forcing."^[1]^: 2232

In turn, radiative forcing is a scientific concept used to quantify and compare the external drivers of change to Earth's energy balance.^[3]^: 1–4 Radiative forcing is the change in energy flux in the atmosphere caused by natural or anthropogenic factors of climate change as measured in watts per meter squared.^[4]

GWP in policymaking

As governments develop policies to combat emissions from high-GWP sources, policymakers have chosen to use the 100-year GWP scale as the standard in international agreements. The Kigali Amendment to the Montreal Protocol sets the global phase-down of hydrofluorocarbons (HFCs), a group of high-GWP compounds. It requires countries to use a set of GWP100 values equal to those published in the IPCC's Fourth Assessment Report (AR4).^[5] This allows policymakers to have one standard for comparison instead of changing GWP values in new assessment reports.^[6] One exception to the GWP100 standard exists: New York state’s Climate Leadership and Community Protection Act requires the use of GWP20, despite being a different standard from all other countries participating in phase downs of HFCs.^[5]

Calculated values

Current values (IPCC Sixth Assessment Report from 2021)

The global warming potential (GWP) depends on both the efficiency of the molecule as a greenhouse gas and its atmospheric lifetime. GWP is measured relative to the same mass of CO₂ and evaluated for a specific timescale.^[8] Thus, if a gas has a high (positive) radiative forcing but also a short lifetime, it will have a large GWP on a 20-year scale but a small one on a 100-year scale. Conversely, if a molecule has a longer atmospheric lifetime than CO₂ its GWP will increase when the timescale is considered. Carbon dioxide is defined to have a GWP of 1 over all time periods.

Methane has an atmospheric lifetime of 12 ± 2 years.^[9]^{: Table 7.15} The 2021 IPCC report lists the GWP as 83 over a time scale of 20 years, 30 over 100 years and 10 over 500 years.^[9]^{: Table 7.15} The decrease in GWP at longer times is because methane decomposes to water and CO₂ through chemical reactions in the atmosphere. Similarly the third most important GHG, nitrous oxide (N₂O), is a common gas emitted through the denitrification part of the nitrogen cycle.^[10] It has a lifetime of 109 years and an even higher GWP level running at 273 over 20 and 100 years.

Examples of the atmospheric lifetime and GWP relative to CO₂ for several greenhouse gases are given in the following table:

Atmospheric lifetime and global warming potential (GWP) relative to CO₂ at different time horizon for various greenhouse gases (more values provided at global warming potential)
Gas name	Chemical formula	Lifetime (years)^[9]^{: Table 7.15}^[11]	Radiative Efficiency (Wm⁻²ppb⁻¹, molar basis).^[9]^{: Table 7.15}^[11]	20 year GWP^[9]^{: Table 7.15}^[11]	100 year GWP^[9]^{: Table 7.15}^[11]	500 year GWP^[9]^{: Table 7.15}^[12]
Carbon dioxide	CO₂	^(A)	1.37×10⁻⁵	1	1	1
Methane (fossil natural gas)	CH ₄	12	5.7×10⁻⁴	83	30	10
Methane (pure non-fossil)	CH ₄	12	5.7×10⁻⁴	81	27	7.3
Nitrous oxide	N ₂O	109	3×10⁻³	273	273	130
CFC-11 (R-11)	CCl ₃F	52	0.29	8321	6226	2093
CFC-12 (R-12)	CCl ₂F ₂	100	0.32	10800	10200	5200
HCFC-22 (R-22)	CHClF ₂	12	0.21	5280	1760	549
HFC-32 (R-32)	CH ₂F ₂	5	0.11	2693	771	220
HFC-134a (R-134a)	CH ₂FCF ₃	14	0.17	4144	1526	436
Tetrafluoromethane (R-14)	CF ₄	50000	0.09	5301	7380	10587
Hexafluoroethane	C ₂F ₆	10 000	0.25	8210	11100	18200
Sulfur hexafluoride	SF ₆	3 200	0.57	17500	23500	32600
Nitrogen trifluoride	NF ₃	500	0.20	12800	16100	20700
^(A) No single lifetime for atmospheric CO₂ can be given.

Estimates of GWP values over 20, 100 and 500 years are periodically compiled and revised in reports from the Intergovernmental Panel on Climate Change. The most recent report is the IPCC Sixth Assessment Report (Working Group I) from 2023.^[9]

The IPCC lists many other substances not shown here.^[13]^[9] ^[14] Some have high GWP but only a low concentration in the atmosphere.

The values given in the table assume the same mass of compound is analyzed; different ratios will result from the conversion of one substance to another. For instance, burning methane to carbon dioxide would reduce the global warming impact, but by a smaller factor than 25:1 because the mass of methane burned is less than the mass of carbon dioxide released (ratio 1:2.74).^[15] For a starting amount of 1 tonne of methane, which has a GWP of 25, after combustion there would be 2.74 tonnes of CO₂, each tonne of which has a GWP of 1. This is a net reduction of 22.26 tonnes of GWP, reducing the global warming effect by a ratio of 25:2.74 (approximately 9 times).

Greenhouse gas	Lifetime (years)	Global warming potential, GWP
Greenhouse gas	Lifetime (years)	20 years	100 years	500 years
Hydrogen (H₂)	4–7^[16]	33 (20–44)^[16]	11 (6–16)^[16]	—
Methane (CH₄)	11.8^[9]	56^[17] 72^[18] 84 / 86f^[13] 96^[19] 80.8 (biogenic)^[9] 82.5 (fossil)^[9]	21^[17] 25^[18] 28 / 34f^[13] 32^[20] 39 (biogenic)^[21] 40 (fossil)^[21]	6.5^[17] 7.6^[18]
Nitrous oxide (N₂O)	109^[9]	280^[17] 289^[18] 264 / 268f^[13] 273^[9]	310^[17] 298^[18] 265 / 298f^[13] 273^[9]	170^[17] 153^[18] 130^[9]
HFC-134a (hydrofluorocarbon)	14.0^[9]	3,710 / 3,790f^[13] 4,144^[9]	1,300 / 1,550f^[13] 1,526^[9]	435^[18] 436^[9]
CFC-11 (chlorofluorocarbon)	52.0^[9]	6,900 / 7,020f^[13] 8,321^[9]	4,660 / 5,350f^[13] 6,226^[9]	1,620^[18] 2,093^[9]
Carbon tetrafluoride (CF₄ / PFC-14)	50,000^[9]	4,880 / 4,950f^[13] 5,301^[9]	6,630 / 7,350f^[13] 7,380^[9]	11,200^[18] 10,587^[9]
HFC-23 (hydrofluorocarbon)	222^[13]	12,000^[18] 10,800^[13]	14,800^[18] 12,400^[13]	12,200^[18]
Sulfur hexafluoride SF₆	3,200^[13]	16,300^[18] 17,500^[13]	22,800^[18] 23,500^[13]	32,600^[18]

Earlier values from 2007

The values provided in the table below are from 2007 when they were published in the IPCC Fourth Assessment Report.^[22]^[18] These values are still used (as of 2020) for some comparisons.^[23]

Greenhouse gas	Chemical formula	100-year Global warming potentials (2007 estimates, for 2013–2020 comparisons)
Carbon dioxide	CO₂	1
Methane	CH₄	25
Nitrous oxide	N₂O	298
Hydrofluorocarbons (HFCs)
HFC-23	CHF₃	14,800
Difluoromethane (HFC-32)	CH₂F₂	675
Fluoromethane (HFC-41)	CH₃F	92
HFC-43-10mee	CF₃CHFCHFCF₂CF₃	1,640
Pentafluoroethane (HFC-125)	C₂HF₅	3,500
HFC-134	C₂H₂F₄ (CHF₂CHF₂)	1,100
1,1,1,2-Tetrafluoroethane (HFC-134a)	C₂H₂F₄ (CH₂FCF₃)	1,430
HFC-143	C₂H₃F₃ (CHF₂CH₂F)	353
1,1,1-Trifluoroethane (HFC-143a)	C₂H₃F₃ (CF₃CH₃)	4,470
HFC-152	CH₂FCH₂F	53
HFC-152a	C₂H₄F₂ (CH₃CHF₂)	124
HFC-161	CH₃CH₂F	12
1,1,1,2,3,3,3-Heptafluoropropane (HFC-227ea)	C₃HF₇	3,220
HFC-236cb	CH₂FCF₂CF₃	1,340
HFC-236ea	CHF₂CHFCF₃	1,370
HFC-236fa	C₃H₂F₆	9,810
HFC-245ca	C₃H₃F₅	693
HFC-245fa	CHF₂CH₂CF₃	1,030
HFC-365mfc	CH₃CF₂CH₂CF₃	794
Perfluorocarbons
Carbon tetrafluoride – PFC-14	CF₄	7,390
Hexafluoroethane – PFC-116	C₂F₆	12,200
Octafluoropropane – PFC-218	C₃F₈	8,830
Perfluorobutane – PFC-3-1-10	C₄F₁₀	8,860
Octafluorocyclobutane – PFC-318	c-C₄F₈	10,300
Perfluouropentane – PFC-4-1-12	C₅F₁₂	9,160
Perfluorohexane – PFC-5-1-14	C₆F₁₄	9,300
Perfluorodecalin – PFC-9-1-18b	C₁₀F₁₈	7,500
Perfluorocyclopropane	c-C₃F₆	17,340
Sulfur hexafluoride (SF₆)
Sulfur hexafluoride	SF₆	22,800
Nitrogen trifluoride (NF₃)
Nitrogen trifluoride	NF₃	17,200
Fluorinated ethers
HFE-125	CHF₂OCF₃	14,900
Bis(difluoromethyl) ether (HFE-134)	CHF₂OCHF₂	6,320
HFE-143a	CH₃OCF₃	756
HCFE-235da2	CHF₂OCHClCF₃	350
HFE-245cb2	CH₃OCF₂CF₃	708
HFE-245fa2	CHF₂OCH₂CF₃	659
HFE-254cb2	CH₃OCF₂CHF₂	359
HFE-347mcc3	CH₃OCF₂CF₂CF₃	575
HFE-347pcf2	CHF₂CF₂OCH₂CF₃	580
HFE-356pcc3	CH₃OCF₂CF₂CHF₂	110
HFE-449sl (HFE-7100)	C₄F₉OCH₃	297
HFE-569sf2 (HFE-7200)	C₄F9OC₂H₅	59
HFE-43-10pccc124 (H-Galden 1040x)	CHF₂OCF₂OC₂F₄OCHF₂	1,870
HFE-236ca12 (HG-10)	CHF₂OCF₂OCHF₂	2,800
HFE-338pcc13 (HG-01)	CHF₂OCF₂CF₂OCHF₂	1,500
	(CF₃)₂CFOCH₃	343
	CF₃CF₂CH₂OH	42
	(CF₃)₂CHOH	195
HFE-227ea	CF₃CHFOCF₃	1,540
HFE-236ea2	CHF₂OCHFCF₃	989
HFE-236fa	CF₃CH₂OCF₃	487
HFE-245fa1	CHF₂CH₂OCF₃	286
HFE-263fb2	CF₃CH₂OCH₃	11
HFE-329mcc2	CHF₂CF₂OCF₂CF₃	919
HFE-338mcf2	CF₃CH₂OCF₂CF₃	552
HFE-347mcf2	CHF₂CH₂OCF₂CF₃	374
HFE-356mec3	CH₃OCF₂CHFCF₃	101
HFE-356pcf2	CHF₂CH₂OCF₂CHF₂	265
HFE-356pcf3	CHF₂OCH₂CF₂CHF₂	502
HFE-365mcfI’ll t3	CF₃CF₂CH₂OCH₃	11
HFE-374pc2	CHF₂CF₂OCH₂CH₃	557
	– (CF₂)₄CH (OH) –	73
	(CF₃)₂CHOCHF₂	380
	(CF₃)₂CHOCH₃	27
Perfluoropolyethers
PFPMIE	CF₃OCF(CF₃)CF₂OCF₂OCF₃	10,300
Trifluoromethyl sulfur pentafluoride	SF₅CF₃	17,400

Importance of time horizon

A substance's GWP depends on the number of years (denoted by a subscript) over which the potential is calculated. A gas which is quickly removed from the atmosphere may initially have a large effect, but for longer time periods, as it has been removed, it becomes less important. Thus methane has a potential of 25 over 100 years (GWP₁₀₀ = 25) but 86 over 20 years (GWP₂₀ = 86); conversely sulfur hexafluoride has a GWP of 22,800 over 100 years but 16,300 over 20 years (IPCC Third Assessment Report). The GWP value depends on how the gas concentration decays over time in the atmosphere. This is often not precisely known and hence the values should not be considered exact. For this reason when quoting a GWP it is important to give a reference to the calculation.

The GWP for a mixture of gases can be obtained from the mass-fraction-weighted average of the GWPs of the individual gases.^[24]

Commonly, a time horizon of 100 years is used by regulators.^[25]^[26]

Water vapour

Water vapour does contribute to anthropogenic global warming, but as the GWP is defined, it is negligible for H₂O: an estimate gives a 100-year GWP between -0.001 and 0.0005.^[27]

H₂O can function as a greenhouse gas because it has a profound infrared absorption spectrum with more and broader absorption bands than CO₂. Its concentration in the atmosphere is limited by air temperature, so that radiative forcing by water vapour increases with global warming (positive feedback). But the GWP definition excludes indirect effects. GWP definition is also based on emissions, and anthropogenic emissions of water vapour (cooling towers, irrigation) are removed via precipitation within weeks, so its GWP is negligible.

Calculation methods

When calculating the GWP of a greenhouse gas, the value depends on the following factors:

the absorption of infrared radiation by the given gas
the time horizon of interest (integration period)
the atmospheric lifetime of the gas

A high GWP correlates with a large infrared absorption and a long atmospheric lifetime. The dependence of GWP on the wavelength of absorption is more complicated. Even if a gas absorbs radiation efficiently at a certain wavelength, this may not affect its GWP much, if the atmosphere already absorbs most radiation at that wavelength. A gas has the most effect if it absorbs in a "window" of wavelengths where the atmosphere is fairly transparent. The dependence of GWP as a function of wavelength has been found empirically and published as a graph.^[31]

Because the GWP of a greenhouse gas depends directly on its infrared spectrum, the use of infrared spectroscopy to study greenhouse gases is centrally important in the effort to understand the impact of human activities on global climate change.

Just as radiative forcing provides a simplified means of comparing the various factors that are believed to influence the climate system to one another, global warming potentials (GWPs) are one type of simplified index based upon radiative properties that can be used to estimate the potential future impacts of emissions of different gases upon the climate system in a relative sense. GWP is based on a number of factors, including the radiative efficiency (infrared-absorbing ability) of each gas relative to that of carbon dioxide, as well as the decay rate of each gas (the amount removed from the atmosphere over a given number of years) relative to that of carbon dioxide.^[32]

The radiative forcing capacity (RF) is the amount of energy per unit area, per unit time, absorbed by the greenhouse gas, that would otherwise be lost to space. It can be expressed by the formula:

${\mathit {RF}}=\sum _{i=1}^{100}{\text{abs}}_{i}\cdot F_{i}/\left({\text{l}}\cdot {\text{d}}\right)$ where the subscript i represents a wavenumber interval of 10 inverse centimeters. Abs_i represents the integrated infrared absorbance of the sample in that interval, and F_i represents the RF for that interval.^{[citation needed]}

The Intergovernmental Panel on Climate Change (IPCC) provides the generally accepted values for GWP, which changed slightly between 1996 and 2001, except for methane, which had its GWP almost doubled. An exact definition of how GWP is calculated is to be found in the IPCC's 2001 Third Assessment Report.^[33] The GWP is defined as the ratio of the time-integrated radiative forcing from the instantaneous release of 1 kg of a trace substance relative to that of 1 kg of a reference gas:

${\mathit {GWP}}\left(x\right)={\frac {a_{x}}{a_{r}}}{\frac {\int _{0}^{\mathit {TH}}[x](t)\,dt}{\int _{0}^{\mathit {TH}}[r](t)\,dt}}$ where TH is the time horizon over which the calculation is considered; a_x is the radiative efficiency due to a unit increase in atmospheric abundance of the substance (i.e., Wm⁻² kg⁻¹) and [x](t) is the time-dependent decay in abundance of the substance following an instantaneous release of it at time t=0. The denominator contains the corresponding quantities for the reference gas (i.e. CO₂). The radiative efficiencies a_x and a_r are not necessarily constant over time. While the absorption of infrared radiation by many greenhouse gases varies linearly with their abundance, a few important ones display non-linear behaviour for current and likely future abundances (e.g., CO₂, CH₄, and N₂O). For those gases, the relative radiative forcing will depend upon abundance and hence upon the future scenario adopted.

Since all GWP calculations are a comparison to CO₂ which is non-linear, all GWP values are affected. Assuming otherwise as is done above will lead to lower GWPs for other gases than a more detailed approach would. Clarifying this, while increasing CO₂ has less and less effect on radiative absorption as ppm concentrations rise, more powerful greenhouse gases like methane and nitrous oxide have different thermal absorption frequencies to CO₂ that are not filled up (saturated) as much as CO₂, so rising ppms of these gases are far more significant.

Applications

Carbon dioxide equivalent

Carbon dioxide equivalent (CO₂e or CO₂eq or CO₂-e) of a quantity of gas is calculated from its GWP. For any gas, it is the mass of CO₂ which would warm the earth as much as the mass of that gas.^[34] Thus it provides a common scale for measuring the climate effects of different gases. It is calculated as GWP multiplied by mass of the other gas. For example, if a gas has GWP of 100, two tonnes of the gas have CO₂e of 200 tonnes, and 9 tonnes of the gas has CO₂e of 900 tonnes.

On a global scale, the warming effects of one or more greenhouse gases in the atmosphere can also be expressed as an equivalent atmospheric concentration of CO₂. CO₂e can then be the atmospheric concentration of CO₂ which would warm the earth as much as a particular concentration of some other gas or of all gases and aerosols in the atmosphere. For example, CO₂e of 500 parts per million would reflect a mix of atmospheric gases which warm the earth as much as 500 parts per million of CO₂ would warm it.^[35]^[36] Calculation of the equivalent atmospheric concentration of CO₂ of an atmospheric greenhouse gas or aerosol is more complex and involves the atmospheric concentrations of those gases, their GWPs, and the ratios of their molar masses to the molar mass of CO₂.

CO₂e calculations depend on the time-scale chosen, typically 100 years or 20 years,^[37]^[38] since gases decay in the atmosphere or are absorbed naturally, at different rates.

The following units are commonly used:

By the UN climate change panel (IPCC): billion metric tonnes = n×10⁹ tonnes of CO₂ equivalent (GtCO₂eq)^[39]
In industry: million metric tonnes of carbon dioxide equivalents (MMTCDE)^[40] and MMT CO₂eq.^[23]
For vehicles: grams of carbon dioxide equivalent per mile (gCO₂e/mile) or per kilometer (gCO₂e/km)^[41]^[42]

For example, the table above shows GWP for methane over 20 years at 86 and nitrous oxide at 289, so emissions of 1 million tonnes of methane or nitrous oxide are equivalent to emissions of 86 or 289 million tonnes of carbon dioxide, respectively.

Use in Kyoto Protocol and for reporting to UNFCCC

Under the Kyoto Protocol, in 1997 the Conference of the Parties standardized international reporting, by deciding (see decision number 2/CP.3) that the values of GWP calculated for the IPCC Second Assessment Report were to be used for converting the various greenhouse gas emissions into comparable CO₂ equivalents.^[43]^[44]

After some intermediate updates, in 2013 this standard was updated by the Warsaw meeting of the UN Framework Convention on Climate Change (UNFCCC, decision number 24/CP.19) to require using a new set of 100-year GWP values. They published these values in Annex III, and they took them from the IPCC Fourth Assessment Report, which had been published in 2007.^[22] Those 2007 estimates are still used for international comparisons through 2020,^[23] although the latest research on warming effects has found other values, as shown in the tables above.

Though recent reports reflect more scientific accuracy, countries and companies continue to use the IPCC Second Assessment Report (SAR)^[17] and IPCC Fourth Assessment Report values for reasons of comparison in their emission reports. The IPCC Fifth Assessment Report has skipped the 500-year values but introduced GWP estimations including the climate-carbon feedback (f) with a large amount of uncertainty.^[13]

Other metrics to compare greenhouse gases

The Global Temperature change Potential (GTP) is another way to compare gases. While GWP estimates infrared thermal radiation absorbed, GTP estimates the resulting rise in average surface temperature of the world, over the next 20, 50 or 100 years, caused by a greenhouse gas, relative to the temperature rise which the same mass of CO₂ would cause.^[13] Calculation of GTP requires modelling how the world, especially the oceans, will absorb heat.^[25] GTP is published in the same IPCC tables with GWP.^[13]

Another metric called GWP* (pronounced "GWP star"^[45]) has been proposed to take better account of short-lived climate pollutants (SLCPs) such as methane. A permanent increase in the rate of emission of an SLCP has a similar effect to that of a one-time emission of an amount of carbon dioxide, because both raise the radiative forcing permanently or (in the case of carbon dioxide) practically permanently (since the CO₂ stays in the air for a long time). GWP* therefore assigns an increase in emission rate of an SLCP a supposedly equivalent amount (tonnes) of CO₂.^[46] However GWP* has been criticised both for its suitability as a metric and for inherent design features which can perpetuate injustices and inequity. Developing countries whose emissions of SLCPs are increasing are "penalized", while developed countries such as Australia or New Zealand which have steady emissions of SLCPs are not penalized in this way, though they may be penalized for their emissions of CO₂.^[47]^[48]^[45]

References

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^ IPCC, 2021: Annex VII: Glossary [Matthews, J.B.R., V. Möller, R. van Diemen, J.S. Fuglestvedt, V. Masson-Delmotte, C. Méndez, S. Semenov, A. Reisinger (eds.)]. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 2215–2256, doi:10.1017/9781009157896.022.
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^ ^a ^b ^c ^d "Appendix 8.A" (PDF). Intergovernmental Panel on Climate Change Fifth Assessment Report. p. 731. Archived (PDF) from the original on 13 October 2017. Retrieved 6 November 2017.
^ "Table 2.14" (PDF). IPCC Fourth Assessment Report. p. 212. Archived (PDF) from the original on 15 December 2007. Retrieved 16 December 2008.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s ^t IPCC AR5 WG1 Ch8 2013, pp. 714, 731.
^ "IPCC Sixth Assessment Report: The Physical Science Basis Ch7.Supp Mat Table 7" (PDF). Archived from the original (PDF) on 30 June 2024.
^ This is so, because of the reaction formula: CH₄ + 2O₂ → CO₂ + 2 H₂O. As mentioned in the article, the oxygen and water is not considered for GWP purposes, and one molecule of methane (molar mass = 16.04 g mol⁻¹) will yield one molecule of carbon dioxide (molar mass = 44.01 g mol⁻¹). This gives a mass ratio of 2.74. (44.01/16.04 ≈ 2.74).
^ ^a ^b ^c Warwick, Nicola; Griffiths, Paul; Keeble, James; Archibald, Alexander; John, Pile (2022-04-08). Atmospheric implications of increased hydrogen use (Report). UK Department for Business, Energy & Industrial Strategy (BEIS).
^ ^a ^b ^c ^d ^e ^f ^g IPCC SAR WG1 Ch2 1995, p. 121.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p IPCC AR4 WG1 Ch2 2007, p. 212.
^ Alvarez (2018). "Assessment of methane emissions from the U.S. oil and gas supply chain". Science. 361 (6398): 186–188. Bibcode:2018Sci...361..186A. doi:10.1126/science.aar7204. PMC 6223263. PMID 29930092.
^ Etminan, M.; Myhre, G.; Highwood, E. J.; Shine, K. P. (28 December 2016). "Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing". Geophysical Research Letters. 43 (24). Bibcode:2016GeoRL..4312614E. doi:10.1002/2016GL071930.
^ ^a ^b Morton, Adam (26 August 2020). "Methane released in gas production means Australia's emissions may be 10% higher than reported". The Guardian.
^ ^a ^b "Report of the Conference of the Parties on its 19th Session" (PDF). UNFCCC. 2014-01-31. Archived (PDF) from the original on 2014-07-13. Retrieved 2020-07-01.
^ ^a ^b ^c "Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2018, p. ES-3" (PDF). US Environmental Protection Agency. 2020-04-13. Archived (PDF) from the original on 2020-04-14. Retrieved 2020-07-01.
^ Regulation (EU) No 517/2014 of the European Parliament and of the Council of 16 April 2014 on fluorinated greenhouse gases Annex IV.
^ ^a ^b "Understanding Global Warming Potentials". United States Environmental Protection Agency. 12 January 2016. Retrieved 2021-03-02.
^ Abernethy, Sam; Jackson, Robert B (February 2022). "Global temperature goals should determine the time horizons for greenhouse gas emission metrics". Environmental Research Letters. 17 (2): 024019. arXiv:2104.05506. Bibcode:2022ERL....17b4019A. doi:10.1088/1748-9326/ac4940. S2CID 233209965.
^ Sherwood, Steven C.; Dixit, Vishal; Salomez, Chryséis (2018). "The global warming potential of near-surface emitted water vapour". Environmental Research Letters. 13 (10): 104006. Bibcode:2018ERL....13j4006S. doi:10.1088/1748-9326/aae018. hdl:1959.4/unsworks_57193. S2CID 158806342.
^ "The NOAA Annual Greenhouse Gas Index (AGGI)". NOAA.gov. National Oceanic and Atmospheric Administration (NOAA). 2024. Archived from the original on 5 October 2024.
^ "Annual Greenhouse Gas Index". U.S. Global Change Research Program. Archived from the original on 21 April 2021. Retrieved 5 September 2020.
^ Butler J. and Montzka S. (2020). "The NOAA Annual Greenhouse Gas Index (AGGI)". NOAA Global Monitoring Laboratory/Earth System Research Laboratories. Archived from the original on 22 September 2013. Retrieved 5 September 2020.
^ Matthew Elrod, "Greenhouse Warming Potential Model." Based on Elrod, M. J. (1999). "Greenhouse Warming Potentials from the Infrared Spectroscopy of Atmospheric Gases". Journal of Chemical Education. 76 (12): 1702. Bibcode:1999JChEd..76.1702E. doi:10.1021/ed076p1702.
^ "Glossary: Global warming potential (GWP)". U.S. Energy Information Administration. Retrieved 2011-04-26. An index used to compare the relative radiative forcing of different gases without directly calculating the changes in atmospheric concentrations. GWPs are calculated as the ratio of the radiative forcing that would result from the emission of one kilogram of a greenhouse gas to that from the emission of one kilogram of carbon dioxide over a fixed period of time, such as 100 years.
^ "Climate Change 2001: The Scientific Basis". www.grida.no. Archived from the original on 31 January 2016. Retrieved 11 January 2022.
^ "CO2e". www3.epa.gov. Retrieved 2020-06-27.
^ "Atmospheric greenhouse gas concentrations – Rationale". European Environment Agency. 2020-02-25. Retrieved 2020-06-28.
^ Gohar, L. K.; Shine, K. P. (November 2007). "Equivalent CO₂ and its use in understanding the climate effects of increased greenhouse gas concentrations". Weather. 62 (11): 307–311. Bibcode:2007Wthr...62..307G. doi:10.1002/wea.103.
^ Wedderburn-Bisshop, Gerard; Longmire, Andrew; Rickards, Lauren (2015). "Neglected Transformational Responses: Implications of Excluding Short Lived Emissions and Near Term Projections in Greenhouse Gas Accounting". The International Journal of Climate Change: Impacts and Responses. 7 (3): 11–27. doi:10.18848/1835-7156/CGP/v07i03/37242. ProQuest 2794017083.
^ Ocko, Ilissa B.; Hamburg, Steven P.; Jacob, Daniel J.; Keith, David W.; Keohane, Nathaniel O.; Oppenheimer, Michael; Roy-Mayhew, Joseph D.; Schrag, Daniel P.; Pacala, Stephen W. (5 May 2017). "Unmask temporal trade-offs in climate policy debates". Science. 356 (6337): 492–493. Bibcode:2017Sci...356..492O. doi:10.1126/science.aaj2350. PMID 28473552. S2CID 206653952.
^ Denison, Steve; Forster, Piers M; Smith, Christopher J (December 2019). "Guidance on emissions metrics for nationally determined contributions under the Paris Agreement". Environmental Research Letters. 14 (12): 124002. Bibcode:2019ERL....14l4002D. doi:10.1088/1748-9326/ab4df4.
^ "Glossary:Carbon dioxide equivalent – Statistics Explained". ec.europa.eu. Retrieved 2020-06-28.
^ "How Clean is Your Electric Vehicle?". Union of Concerned Scientists. Retrieved 2020-07-02.
^ Whitehead, Jake (2019-09-07). "The Truth About Electric Vehicle Emissions". www.realclearscience.com. Retrieved 2020-07-02.
^ Conference of the Parties (25 March 1998). "Methodological issues related to the Kyoto Protocol". Report of the Conference of the Parties on its third session, held at Kyoto from 1 to 11 December 1997 Addendum Part Two: Action taken by the Conference of the Parties at its third session (PDF). UNFCCC. Archived (PDF) from the original on 2000-08-23. Retrieved 17 January 2011.
^ Godal, Odd; Fuglestvedt, Jan (2002). "Testing 100-year global warming potentials: Impacts on compliance costs and abatement profile". Climatic Change. 52 (1/2): 93–127. doi:10.1023/A:1013086803762. S2CID 150488348. ProQuest 198550594.
^ ^a ^b Rogelj, Joeri; Schleussner, Carl-Friedrich (1 June 2021). "Reply to Comment on 'Unintentional unfairness when applying new greenhouse gas emissions metrics at country level'". Environmental Research Letters. 16 (6): 068002. Bibcode:2021ERL....16f8002R. doi:10.1088/1748-9326/ac02ec.
^ Lynch, John; Cain, Michelle; Pierrehumbert, Raymond; Allen, Myles (April 2020). "Demonstrating GWP*: a means of reporting warming-equivalent emissions that captures the contrasting impacts of short- and long-lived climate pollutants". Environmental Research Letters. 15 (4): 044023. Bibcode:2020ERL....15d4023L. doi:10.1088/1748-9326/ab6d7e. PMC 7212016. PMID 32395177.
^ Meinshausen, Malte; Nicholls, Zebedee (1 April 2022). "GWP*is a model, not a metric". Environmental Research Letters. 17 (4): 041002. Bibcode:2022ERL....17d1002M. doi:10.1088/1748-9326/ac5930.
^ Rogelj, Joeri; Schleussner, Carl-Friedrich (1 November 2019). "Unintentional unfairness when applying new greenhouse gas emissions metrics at country level". Environmental Research Letters. 14 (11): 114039. Bibcode:2019ERL....14k4039R. doi:10.1088/1748-9326/ab4928. hdl:10044/1/77353. S2CID 250668916.

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Schimel, D.; Alves, D.; Enting, I.; Heimann, M.; et al. (1995). "Chapter 2: Radiative Forcing of Climate Change". Climate Change 1995: The Science of Climate Change. Contribution of Working Group I to the Second Assessment Report of the Intergovernmental Panel on Climate Change (IPCC SAR WG1). pp. 65–132.
Forster, P.; Ramaswamy, V.; Artaxo, P.; Berntsen, T.; et al. (2007). "Chapter 2: Changes in Atmospheric Constituents and Radiative Forcing" (PDF). Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 129–234.
Myhre, G.; Shindell, D.; Bréon, F.-M.; Collins, W.; et al. (2013). "Chapter 8: Anthropogenic and Natural Radiative Forcing" (PDF). Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. pp. 659–740.

External links

List of Global Warming Potentials and Atmospheric Lifetimes from the U.S. EPA
GWP and the different meanings of CO₂e explained

[:2-1] IPCC, 2021: Annex VII: Glossary [Matthews, J.B.R., V. Möller, R. van Diemen, J.S. Fuglestvedt, V. Masson-Delmotte, C. Méndez, S. Semenov, A. Reisinger (eds.)]. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 2215–2256, doi:10.1017/9781009157896.022.

[:0-2] 7.SM.6 Tables of greenhouse gas lifetimes, radiative efficiencies and metrics (PDF), IPCC, 2021, p. 7SM-24.

[nrcrf-3] National Research Council (2005). Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. The National Academic Press. doi:10.17226/11175. ISBN 978-0-309-09506-8.

[4] Drew, Shindell (2013). "Climate Change 2013: The Physical Science Basis – Working Group 1 contribution to the IPCC Fifth Assessment Report: Radiative Forcing in the AR5" (PDF). Department of Environmental Sciences, School of Environmental and Biological Sciences. envsci.rutgers.edu. Rutgers University. Fifth Assessment Report (AR5). Archived (PDF) from the original on 4 March 2016. Retrieved 15 September 2016.

[:5-5] Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer (the "Montreal Protocol"), adopted at Kigali on October 15, 2016, by the Twenty-Eighth Meeting of the Parties to the Montreal Protocol (the "Kigali Amendment").

[6] "Understanding Global Warming Potentials". US EPA, Greenhouse Gas Emissions. August 8, 2024. Retrieved August 26, 2024.

[7] "Global warming potential of greenhouse gases relative to CO2". Our World in Data. Retrieved 2023-12-18.

[:02-8] IPCC, 2021: Annex VII: Glossary [Matthews, J.B.R., V. Möller, R. van Diemen, J.S. Fuglestvedt, V. Masson-Delmotte, C. Méndez, S. Semenov, A. Reisinger (eds.)]. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 2215–2256, doi:10.1017/9781009157896.022.

[ar6_WG1_Ch_7-9] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s ^t ^u ^v ^w ^x ^y ^z ^aa ^ab Forster, P., T. Storelvmo, K. Armour, W. Collins, J.-L. Dufresne, D. Frame, D.J. Lunt, T. Mauritsen, M.D. Palmer, M. Watanabe, M. Wild, and H. Zhang, 2021: Chapter 7: The Earth's Energy Budget, Climate Feedbacks, and Climate Sensitivity. In https://www.ipcc.ch/report/ar6/wg1/ [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 923–1054, doi:10.1017/9781009157896.009.

[10] Yang, Rui; Yuan, Lin-jiang; Wang, Ru; He, Zhi-xian; Lei, Lin; Ma, Yan-chen (2022). "Analyzing the mechanism of nitrous oxide production in aerobic phase of anoxic/aerobic sequential batch reactor from the perspective of key enzymes". Environmental Science and Pollution Research. 29 (26): 39877–39887. doi:10.1007/s11356-022-18800-3. ISSN 0944-1344.

[TableOfWarmingPotentials5-11] "Appendix 8.A" (PDF). Intergovernmental Panel on Climate Change Fifth Assessment Report. p. 731. Archived (PDF) from the original on 13 October 2017. Retrieved 6 November 2017.

[TableOfWarmingPotentials-12] "Table 2.14" (PDF). IPCC Fourth Assessment Report. p. 212. Archived (PDF) from the original on 15 December 2007. Retrieved 16 December 2008.

[ar5-13] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s ^t IPCC AR5 WG1 Ch8 2013, pp. 714, 731.

[14] "IPCC Sixth Assessment Report: The Physical Science Basis Ch7.Supp Mat Table 7" (PDF). Archived from the original (PDF) on 30 June 2024.

[15] This is so, because of the reaction formula: CH₄ + 2O₂ → CO₂ + 2 H₂O. As mentioned in the article, the oxygen and water is not considered for GWP purposes, and one molecule of methane (molar mass = 16.04 g mol⁻¹) will yield one molecule of carbon dioxide (molar mass = 44.01 g mol⁻¹). This gives a mass ratio of 2.74. (44.01/16.04 ≈ 2.74).

[:3-16] Warwick, Nicola; Griffiths, Paul; Keeble, James; Archibald, Alexander; John, Pile (2022-04-08). Atmospheric implications of increased hydrogen use (Report). UK Department for Business, Energy & Industrial Strategy (BEIS).

[sar-17] ^ ^a ^b ^c ^d ^e ^f ^g IPCC SAR WG1 Ch2 1995, p. 121.

[ar4-18] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p IPCC AR4 WG1 Ch2 2007, p. 212.

[19] Alvarez (2018). "Assessment of methane emissions from the U.S. oil and gas supply chain". Science. 361 (6398): 186–188. Bibcode:2018Sci...361..186A. doi:10.1126/science.aar7204. PMC 6223263. PMID 29930092.

[20] Etminan, M.; Myhre, G.; Highwood, E. J.; Shine, K. P. (28 December 2016). "Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing". Geophysical Research Letters. 43 (24). Bibcode:2016GeoRL..4312614E. doi:10.1002/2016GL071930.

[:4-21] Morton, Adam (26 August 2020). "Methane released in gas production means Australia's emissions may be 10% higher than reported". The Guardian.

[unfccc19-22] "Report of the Conference of the Parties on its 19th Session" (PDF). UNFCCC. 2014-01-31. Archived (PDF) from the original on 2014-07-13. Retrieved 2020-07-01.

[epa20-23] "Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2018, p. ES-3" (PDF). US Environmental Protection Agency. 2020-04-13. Archived (PDF) from the original on 2020-04-14. Retrieved 2020-07-01.

[24] Regulation (EU) No 517/2014 of the European Parliament and of the Council of 16 April 2014 on fluorinated greenhouse gases Annex IV.

[:1-25] "Understanding Global Warming Potentials". United States Environmental Protection Agency. 12 January 2016. Retrieved 2021-03-02.

[26] Abernethy, Sam; Jackson, Robert B (February 2022). "Global temperature goals should determine the time horizons for greenhouse gas emission metrics". Environmental Research Letters. 17 (2): 024019. arXiv:2104.05506. Bibcode:2022ERL....17b4019A. doi:10.1088/1748-9326/ac4940. S2CID 233209965.

[27] Sherwood, Steven C.; Dixit, Vishal; Salomez, Chryséis (2018). "The global warming potential of near-surface emitted water vapour". Environmental Research Letters. 13 (10): 104006. Bibcode:2018ERL....13j4006S. doi:10.1088/1748-9326/aae018. hdl:1959.4/unsworks_57193. S2CID 158806342.

[NOAA_AGGI_2023-28] "The NOAA Annual Greenhouse Gas Index (AGGI)". NOAA.gov. National Oceanic and Atmospheric Administration (NOAA). 2024. Archived from the original on 5 October 2024.

[29] "Annual Greenhouse Gas Index". U.S. Global Change Research Program. Archived from the original on 21 April 2021. Retrieved 5 September 2020.

[butmon-30] Butler J. and Montzka S. (2020). "The NOAA Annual Greenhouse Gas Index (AGGI)". NOAA Global Monitoring Laboratory/Earth System Research Laboratories. Archived from the original on 22 September 2013. Retrieved 5 September 2020.

[31] Matthew Elrod, "Greenhouse Warming Potential Model." Based on Elrod, M. J. (1999). "Greenhouse Warming Potentials from the Infrared Spectroscopy of Atmospheric Gases". Journal of Chemical Education. 76 (12): 1702. Bibcode:1999JChEd..76.1702E. doi:10.1021/ed076p1702.

[32] "Glossary: Global warming potential (GWP)". U.S. Energy Information Administration. Retrieved 2011-04-26. An index used to compare the relative radiative forcing of different gases without directly calculating the changes in atmospheric concentrations. GWPs are calculated as the ratio of the radiative forcing that would result from the emission of one kilogram of a greenhouse gas to that from the emission of one kilogram of carbon dioxide over a fixed period of time, such as 100 years.

[33] "Climate Change 2001: The Scientific Basis". www.grida.no. Archived from the original on 31 January 2016. Retrieved 11 January 2022.

[epadef-34] "CO2e". www3.epa.gov. Retrieved 2020-06-27.

[eea-35] "Atmospheric greenhouse gas concentrations – Rationale". European Environment Agency. 2020-02-25. Retrieved 2020-06-28.

[rmets-36] Gohar, L. K.; Shine, K. P. (November 2007). "Equivalent CO₂ and its use in understanding the climate effects of increased greenhouse gas concentrations". Weather. 62 (11): 307–311. Bibcode:2007Wthr...62..307G. doi:10.1002/wea.103.

[Wedderburn-Bisshop_et_al_2015-37] Wedderburn-Bisshop, Gerard; Longmire, Andrew; Rickards, Lauren (2015). "Neglected Transformational Responses: Implications of Excluding Short Lived Emissions and Near Term Projections in Greenhouse Gas Accounting". The International Journal of Climate Change: Impacts and Responses. 7 (3): 11–27. doi:10.18848/1835-7156/CGP/v07i03/37242. ProQuest 2794017083.

[OckoHamburg2017-38] Ocko, Ilissa B.; Hamburg, Steven P.; Jacob, Daniel J.; Keith, David W.; Keohane, Nathaniel O.; Oppenheimer, Michael; Roy-Mayhew, Joseph D.; Schrag, Daniel P.; Pacala, Stephen W. (5 May 2017). "Unmask temporal trade-offs in climate policy debates". Science. 356 (6337): 492–493. Bibcode:2017Sci...356..492O. doi:10.1126/science.aaj2350. PMID 28473552. S2CID 206653952.

[39] Denison, Steve; Forster, Piers M; Smith, Christopher J (December 2019). "Guidance on emissions metrics for nationally determined contributions under the Paris Agreement". Environmental Research Letters. 14 (12): 124002. Bibcode:2019ERL....14l4002D. doi:10.1088/1748-9326/ab4df4.

[40] "Glossary:Carbon dioxide equivalent – Statistics Explained". ec.europa.eu. Retrieved 2020-06-28.

[ucs-ev-41] "How Clean is Your Electric Vehicle?". Union of Concerned Scientists. Retrieved 2020-07-02.

[rcs-42] Whitehead, Jake (2019-09-07). "The Truth About Electric Vehicle Emissions". www.realclearscience.com. Retrieved 2020-07-02.

[43] Conference of the Parties (25 March 1998). "Methodological issues related to the Kyoto Protocol". Report of the Conference of the Parties on its third session, held at Kyoto from 1 to 11 December 1997 Addendum Part Two: Action taken by the Conference of the Parties at its third session (PDF). UNFCCC. Archived (PDF) from the original on 2000-08-23. Retrieved 17 January 2011.

[44] Godal, Odd; Fuglestvedt, Jan (2002). "Testing 100-year global warming potentials: Impacts on compliance costs and abatement profile". Climatic Change. 52 (1/2): 93–127. doi:10.1023/A:1013086803762. S2CID 150488348. ProQuest 198550594.

[Reply-45] Rogelj, Joeri; Schleussner, Carl-Friedrich (1 June 2021). "Reply to Comment on 'Unintentional unfairness when applying new greenhouse gas emissions metrics at country level'". Environmental Research Letters. 16 (6): 068002. Bibcode:2021ERL....16f8002R. doi:10.1088/1748-9326/ac02ec.

[46] Lynch, John; Cain, Michelle; Pierrehumbert, Raymond; Allen, Myles (April 2020). "Demonstrating GWP*: a means of reporting warming-equivalent emissions that captures the contrasting impacts of short- and long-lived climate pollutants". Environmental Research Letters. 15 (4): 044023. Bibcode:2020ERL....15d4023L. doi:10.1088/1748-9326/ab6d7e. PMC 7212016. PMID 32395177.

[47] Meinshausen, Malte; Nicholls, Zebedee (1 April 2022). "GWP*is a model, not a metric". Environmental Research Letters. 17 (4): 041002. Bibcode:2022ERL....17d1002M. doi:10.1088/1748-9326/ac5930.

[48] Rogelj, Joeri; Schleussner, Carl-Friedrich (1 November 2019). "Unintentional unfairness when applying new greenhouse gas emissions metrics at country level". Environmental Research Letters. 14 (11): 114039. Bibcode:2019ERL....14k4039R. doi:10.1088/1748-9326/ab4928. hdl:10044/1/77353. S2CID 250668916.

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@@ Line 2: / Line 2: @@
 [[File:Perfluorotributylamine-global-warming-potential.jpg|thumb|Comparison of global warming potential (GWP) of three [[greenhouse gas]]es over a 100-year period: [[Perfluorotributylamine]], [[nitrous oxide]] and [[methane]], compared to [[carbon dioxide]] (the latter is the reference value, therefore it has a GWP of one)]]
-'''Global warming potential''' ('''GWP''') is an index to measure how much [[infrared]] [[thermal radiation]] a [[greenhouse gas]] would absorb over a given time frame after it has been added to the [[atmosphere]] (or ''emitted'' to the atmosphere). The GWP makes different greenhouse gases comparable with regard to their "effectiveness in causing [[radiative forcing]]".<ref name=":2" />{{Rp|page=2232}} It is expressed as a multiple of the radiation that would be absorbed by the same [[mass]] of added [[carbon dioxide]] ({{CO2}}), which is taken as a reference gas. Therefore, the GWP has a value of 1 for {{CO2}}. For other [[gas]]es it depends on how strongly the gas absorbs infrared thermal radiation, how quickly the gas leaves the atmosphere, and the time frame being considered.
+'''Global warming potential''' ('''GWP''') is an index to measure how much [[infrared]] [[thermal radiation]] a [[greenhouse gas]] would absorb over a given time frame after it has been added to the [[atmosphere]] (or ''emitted'' to the atmosphere). The GWP makes different greenhouse gases comparable with regard to their "effectiveness in causing [[radiative forcing]]".<ref name=":2" />{{Rp|page=2232}} It is expressed as a multiple of the [[radiation]] that would be absorbed by the same [[mass]] of added [[carbon dioxide]] ({{CO2}}), which is taken as a reference gas. Therefore, the GWP has a value of 1 for {{CO2}}. For other [[gas]]es it depends on how strongly the gas absorbs infrared thermal radiation, how quickly the gas leaves the atmosphere, and the time frame being considered.
 For example, [[Methane emissions|methane]] has a GWP over 20 years (GWP-20) of 81.2<ref name=":0">{{Citation |title=7.SM.6 Tables of greenhouse gas lifetimes, radiative efficiencies and metrics |date=2021 |url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter_07_Supplementary_Material.pdf |page=7SM-24 |publisher=[[IPCC]]}}.</ref> meaning that, for example, a [[Fugitive gas emissions|leak]] of a tonne of methane is equivalent to emitting 81.2 tonnes of carbon dioxide measured over 20 years. As methane has a much shorter atmospheric lifetime than carbon dioxide, its GWP is much less over longer time periods, with a GWP-100 of 27.9 and a GWP-500 of 7.95.<ref name=":0" />{{Rp|page=7SM-24}}
@@ Line 16: / Line 17: @@
 === GWP in policymaking ===
-As governments develop policies to combat emissions from high-GWP sources, policymakers have chosen to use the 100-year GWP scale as the standard in international agreements. The [[Kigali Amendment]] to the [[Montreal Protocol]] sets the global phase-down of [[Hydrofluorocarbon|hydrofluorocarbons]] (HFCs), a group of high-GWP compounds. It requires countries to use a set of GWP100 values equal to those published in the IPCC’s Fourth Assessment Report (AR4).<ref name=":5">'''[https://treaties.un.org/doc/Treaties/2016/10/20161015%2003-23%20PM/Ch_XXVII-2.f-English%20and%20French.pdf Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer] (the "Montreal Protocol"), adopted at Kigali on October 15, 2016, by the Twenty-Eighth Meeting of the Parties to the Montreal Protocol (the "Kigali Amendment").'''</ref> This allows policymakers to have one standard for comparison instead of changing GWP values in new assessment reports.<ref>{{Cite web |date=August 8, 2024 |title=Understanding Global Warming Potentials |url=https://www.epa.gov/ghgemissions/understanding-global-warming-potentials |url-status=live |access-date=August 26, 2024 |website=US EPA, Greenhouse Gas Emissions}}</ref> One exception to the GWP100 standard exists: [[Government of New York (state)|New York state]]’s [[Climate Leadership and Community Protection Act]] requires the use of GWP20, despite being a different standard from all other countries participating in phase downs of HFCs.<ref name=":5" />
+As governments develop policies to combat emissions from high-GWP sources, policymakers have chosen to use the 100-year GWP scale as the standard in international agreements. The [[Kigali Amendment]] to the [[Montreal Protocol]] sets the global phase-down of [[hydrofluorocarbon]]s (HFCs), a group of high-GWP compounds. It requires countries to use a set of GWP100 values equal to those published in the IPCC's Fourth Assessment Report (AR4).<ref name=":5">'''[https://treaties.un.org/doc/Treaties/2016/10/20161015%2003-23%20PM/Ch_XXVII-2.f-English%20and%20French.pdf Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer] (the "Montreal Protocol"), adopted at Kigali on October 15, 2016, by the Twenty-Eighth Meeting of the Parties to the Montreal Protocol (the "Kigali Amendment").'''</ref> This allows policymakers to have one standard for comparison instead of changing GWP values in new assessment reports.<ref>{{Cite web |date=August 8, 2024 |title=Understanding Global Warming Potentials |url=https://www.epa.gov/ghgemissions/understanding-global-warming-potentials |access-date=August 26, 2024 |website=US EPA, Greenhouse Gas Emissions}}</ref> One exception to the GWP100 standard exists: [[Government of New York (state)|New York state]]’s [[Climate Leadership and Community Protection Act]] requires the use of GWP20, despite being a different standard from all other countries participating in phase downs of HFCs.<ref name=":5" />
 == Calculated values ==
@@ Line 24: / Line 25: @@
 [[File:Global-warming-potential-of-greenhouse-gases-over-100-year-timescale-gwp (OWID 0525).png|thumb|Global warming potential of five greenhouse gases over 100-year timescale.<ref>{{Cite web |title=Global warming potential of greenhouse gases relative to CO2 |url=https://ourworldindata.org/grapher/global-warming-potential-of-greenhouse-gases-over-100-year-timescale-gwp |access-date=2023-12-18 |website=Our World in Data}}</ref>]]The global warming potential (GWP) depends on both the efficiency of the molecule as a greenhouse gas and its atmospheric lifetime. GWP is measured relative to the same mass of {{CO2}} and evaluated for a specific timescale.<ref name=":02">IPCC, 2021: [https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_AnnexVII.pdf Annex VII: Glossary] [Matthews, J.B.R., V. Möller, R. van Diemen, J.S. Fuglestvedt, V. Masson-Delmotte, C.  Méndez, S. Semenov, A. Reisinger (eds.)]. In [https://www.ipcc.ch/report/ar6/wg1/ Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 2215–2256, [[doi:10.1017/9781009157896.022]].</ref> Thus, if a gas has a high (positive) radiative forcing but also a short lifetime, it will have a large GWP on a 20-year scale but a small one on a 100-year scale. Conversely, if a molecule has a longer atmospheric lifetime than {{CO2}} its GWP will increase when the timescale is considered. Carbon dioxide is defined to have a GWP of 1 over all time periods.
-Methane has an atmospheric lifetime of 12 ± 2 years.<ref name="ar6 WG1 Ch 7" />{{rp|Table 7.15}} The [[IPCC Sixth Assessment Report|2021 IPCC report]] lists the GWP as 83 over a time scale of 20 years, 30 over 100 years and 10 over 500 years.<ref name="ar6 WG1 Ch 7" />{{rp|Table 7.15}} The decrease in GWP at longer times is because [[Atmospheric methane#Removal processes|methane]] decomposes to water and {{CO2}} through chemical reactions in the atmosphere. Similarly the third most important GHG, [[nitrous oxide]] (N<sub>2</sub>O), is a common gas emitted through the [[denitrification]] part of the [[nitrogen cycle]].<ref>{{Cite journal |last=Yang |first=Rui |last2=Yuan |first2=Lin-jiang |last3=Wang |first3=Ru |last4=He |first4=Zhi-xian |last5=Lei |first5=Lin |last6=Ma |first6=Yan-chen |date=2022 |title=Analyzing the mechanism of nitrous oxide production in aerobic phase of anoxic/aerobic sequential batch reactor from the perspective of key enzymes |url=https://link.springer.com/10.1007/s11356-022-18800-3 |journal=Environmental Science and Pollution Research |language=en |volume=29 |issue=26 |pages=39877–39887 |doi=10.1007/s11356-022-18800-3 |issn=0944-1344}}</ref> It has a lifetime of 109 years and an even higher GWP level running at 273 over 20 and 100 years.
+Methane has an atmospheric lifetime of 12 ± 2 years.<ref name="ar6 WG1 Ch 7" />{{rp|Table 7.15}} The [[IPCC Sixth Assessment Report|2021 IPCC report]] lists the GWP as 83 over a time scale of 20 years, 30 over 100 years and 10 over 500 years.<ref name="ar6 WG1 Ch 7" />{{rp|Table 7.15}} The decrease in GWP at longer times is because [[Atmospheric methane#Removal processes|methane]] decomposes to water and {{CO2}} through chemical reactions in the atmosphere. Similarly the third most important GHG, [[nitrous oxide]] (N<sub>2</sub>O), is a common gas emitted through the [[denitrification]] part of the [[nitrogen cycle]].<ref>{{Cite journal |last1=Yang |first1=Rui |last2=Yuan |first2=Lin-jiang |last3=Wang |first3=Ru |last4=He |first4=Zhi-xian |last5=Lei |first5=Lin |last6=Ma |first6=Yan-chen |date=2022 |title=Analyzing the mechanism of nitrous oxide production in aerobic phase of anoxic/aerobic sequential batch reactor from the perspective of key enzymes |url=https://link.springer.com/10.1007/s11356-022-18800-3 |journal=Environmental Science and Pollution Research |language=en |volume=29 |issue=26 |pages=39877–39887 |doi=10.1007/s11356-022-18800-3 |issn=0944-1344}}</ref> It has a lifetime of 109 years and an even higher GWP level running at 273 over 20 and 100 years.
 Examples of the atmospheric lifetime and GWP relative to {{CO2}} for several greenhouse gases are given in the following table:
@@ Line 48: / Line 49: @@
 |1
 |-
-| style="text-align:left;" |[[Methane]] (fossil)
+| style="text-align:left;" |[[Methane]] (fossil [[natural gas]])
 | style="text-align:center;" |{{chem|CH|4}}
 |12
@@ Line 56: / Line 57: @@
 |10
 |-
-| style="text-align:left;" |[[Methane]] (non-fossil)
+| style="text-align:left;" |[[Methane]] (pure non-fossil)
 | style="text-align:center;" |{{chem|CH|4}}
 |12
@@ Line 148: / Line 149: @@
 Estimates of GWP values over 20, 100 and 500 years are periodically compiled and revised in reports from the [[Intergovernmental Panel on Climate Change]]. The most recent report is the [[IPCC Sixth Assessment Report]] (Working Group I) from 2023.<ref name="ar6 WG1 Ch 7">Forster, P., T. Storelvmo, K. Armour, W. Collins, J.-L. Dufresne, D. Frame, D.J. Lunt, T. Mauritsen, M.D. Palmer, M. Watanabe, M. Wild, and H. Zhang, 2021: [https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter07.pdf Chapter 7: The Earth's Energy Budget, Climate Feedbacks, and Climate Sensitivity]. In https://www.ipcc.ch/report/ar6/wg1/ [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N.  Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 923–1054, doi:10.1017/9781009157896.009.</ref>
-The IPCC lists many other substances not shown here.<ref name="ar5">{{Harvnb|IPCC AR5 WG1 Ch8|2013|pages=714, 731}}.</ref><ref name="ar6 WG1 Ch 7" /> Some have high GWP but only a low concentration in the atmosphere.
+The IPCC lists many other substances not shown here.<ref name="ar5">{{Harvnb|IPCC AR5 WG1 Ch8|2013|pages=714, 731}}.</ref><ref name="ar6 WG1 Ch 7" /> <ref> {{cite web |title= IPCC Sixth Assessment Report: The Physical Science Basis Ch7.Supp Mat Table 7
+|url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_FGD_Chapter07_SM.pdf
+|archive-url=https://web.archive.org/web/20240630195210/https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_FGD_Chapter07_SM.pdf
+|archive-date=30 June 2024}}</ref> Some have high GWP but only a low concentration in the atmosphere.
 The values given in the table assume the same mass of compound is analyzed; different ratios will result from the conversion of one substance to another. For instance, burning [[methane]] to carbon dioxide would reduce the global warming impact, but by a smaller factor than 25:1 because the mass of [[methane]] burned is less than the mass of [[carbon dioxide]] released (ratio 1:2.74).<ref>This is so, because of the reaction formula: CH<sub>4</sub> + 2O<sub>2</sub> → {{CO2}} + 2 H<sub>2</sub>O. As mentioned in the article, the oxygen and water is not considered for GWP purposes, and one molecule of methane (molar mass = 16.04 g mol<sup>−1</sup>) will yield one molecule of carbon dioxide (molar mass = 44.01 g mol<sup>−1</sup>). This gives a mass ratio of 2.74. (44.01/16.04 ≈ 2.74).</ref> For a starting amount of 1 tonne of methane, which has a GWP of 25, after combustion there would be 2.74 tonnes of {{CO2}}, each tonne of which has a GWP of 1. This is a net reduction of 22.26 tonnes of GWP, reducing the global warming effect by a ratio of 25:2.74 (approximately 9 times).
@@ Line 163: / Line 167: @@
 |[[Hydrogen]] (H<sub>2</sub>)
 |4–7<ref name=":3">{{Cite report |url=https://www.gov.uk/government/publications/atmospheric-implications-of-increased-hydrogen-use |title=Atmospheric implications of increased hydrogen use |last1=Warwick |first1=Nicola |last2=Griffiths |first2=Paul |date=2022-04-08 |publisher=UK Department for Business, Energy & Industrial Strategy (BEIS) |last3=Keeble |first3=James |last4=Archibald |first4=Alexander |last5=John |first5=Pile |ref={{Harvid|Warwick|2022}}}}</ref>
-| data-sort-value="33" | 33 (20-44)<ref name=":3" />
+| data-sort-value="33" | 33 (20–44)<ref name=":3" />
 | data-sort-value="11" | 11 (6–16)<ref name=":3" />|| {{n/a}}
 |-
@@ Line 520: / Line 524: @@
 == Calculation methods ==
-[[File:1979-_Radiative_forcing_-_climate_change_-_global_warming_-_EPA_NOAA.svg|right|thumb|upright=1.6|The [[radiative forcing]] (warming influence) of long-lived atmospheric greenhouse gases has accelerated, almost doubling in 40 years.<ref name="NOAA_AGGI_2022">{{cite web |date=Spring 2023 |title=The NOAA Annual Greenhouse Gas Index (AGGI) |url=https://gml.noaa.gov/aggi/aggi.html |url-status=live |archive-url=https://web.archive.org/web/20230524133553/https://gml.noaa.gov/aggi/aggi.html |archive-date=24 May 2023 |website=NOAA.gov |publisher=National Oceanic and Atmospheric Administration (NOAA)}}</ref><ref>{{Cite web |title=Annual Greenhouse Gas Index |url=https://www.globalchange.gov/browse/indicators/annual-greenhouse-gas-index |url-status=live |archive-url=https://web.archive.org/web/20210421143115/https://www.globalchange.gov/browse/indicators/annual-greenhouse-gas-index |archive-date=21 April 2021 |access-date=5 September 2020 |publisher=U.S. Global Change Research Program}}</ref><ref name="butmon">{{Cite web |author=Butler J. and Montzka S. |year=2020 |title=The NOAA Annual Greenhouse Gas Index (AGGI) |url=https://www.esrl.noaa.gov/gmd/aggi/aggi.html |url-status=live |archive-url=https://web.archive.org/web/20130922035917/https://www.esrl.noaa.gov/gmd/aggi/aggi.html |archive-date=22 September 2013 |access-date=5 September 2020 |publisher=[[NOAA]] Global Monitoring Laboratory/Earth System Research Laboratories}}</ref>]]
+[[File:1979-_Radiative_forcing_-_climate_change_-_global_warming_-_EPA_NOAA.svg|right|thumb|upright=1.6|The [[radiative forcing]] (warming influence) of long-lived atmospheric greenhouse gases has accelerated, almost doubling in 40 years.<ref name=NOAA_AGGI_2023>{{cite web |title=The NOAA Annual Greenhouse Gas Index (AGGI) |url=https://gml.noaa.gov/aggi/aggi.html |website=NOAA.gov |publisher=National Oceanic and Atmospheric Administration (NOAA) |archive-url=https://web.archive.org/web/20241005195609/https://gml.noaa.gov/aggi/aggi.html |archive-date=5 October 2024 |date=2024 |url-status=live }}</ref><ref>{{Cite web |title=Annual Greenhouse Gas Index |url=https://www.globalchange.gov/browse/indicators/annual-greenhouse-gas-index |url-status=live |archive-url=https://web.archive.org/web/20210421143115/https://www.globalchange.gov/browse/indicators/annual-greenhouse-gas-index |archive-date=21 April 2021 |access-date=5 September 2020 |publisher=U.S. Global Change Research Program}}</ref><ref name="butmon">{{Cite web |author=Butler J. and Montzka S. |year=2020 |title=The NOAA Annual Greenhouse Gas Index (AGGI) |url=https://www.esrl.noaa.gov/gmd/aggi/aggi.html |url-status=live |archive-url=https://web.archive.org/web/20130922035917/https://www.esrl.noaa.gov/gmd/aggi/aggi.html |archive-date=22 September 2013 |access-date=5 September 2020 |publisher=[[NOAA]] Global Monitoring Laboratory/Earth System Research Laboratories}}</ref>]]
 When calculating the GWP of a greenhouse gas, the value depends on the following factors:
 * the absorption of [[infrared radiation]] by the given gas