MEMORANDUM 

TO: Jessica Gordan, Debbie Ottinger, EPA 

FROM: Tracy Curtis, Donna Lazzari, ERG 

DATE: February 27, 2013 

SUBJECT: GWP Determinations for Proposed Additional F-GHGs for Table A-1 

EPA is considering to include Global Warning Potentials (GWPs) in Table A-1 of subpart A of 

the GHG reporting rule for 26 new fluorinated greenhouse gases (F-GHGs). Reporters would use the 

GWPs in Table A-1 to subpart A to calculate GHG emissions for threshold applicability, determination of 

calculation methodologies, and reporting of annual emissions in CO2e. This memorandum provides 

background on the EPA’s evaluation of scientific assessments and publically available estimates of GWP 

for the proposed F-GHGs. This memorandum is organized as follows:

1. Background and Overview for Estimation of GWP 

2. Key Considerations in GWP Calculation Methods 

3. Compounds Identified from Provisional GWP Requests and Submitted by Producers 

4. Compounds Identified from Peer-Reviewed Assessments 

5. References 

1.0 BACKGROUND AND OVERVIEW FOR ESTIMATION OF GWP 

Table A-1 to subpart A (“Table A-1”) is a compendium of GWP values of select GHGs that are required 

to be reported under one or more subparts of Part 98, and where the EPA has identified the GWP in the 

IPCC Fourth Assessment Report or other sources. As acknowledged in the final Part 98 (74 FR 56348, 

October 30, 2009), it is EPA’s intent to periodically update Table A-1 as GWPs are evaluated or reevaluated by the scientific community. EPA is proposing to include 26 additional GHGs in Table A-1 

with associated GWP values where the EPA has identified the GWP based on an assessment of recent 
scientific literature. . The EPA identified the proposed compounds and associated GWPs through review 

of provisional GWP requests received from subpart L facilities, F-GHGs submitted by a fluorinated GHG 

producer with suggested GWPs and supporting data and analysis on August 21, 2012, and F-GHGs for 

which evaluations of the GWPs were performed by the EPA (e.g, as part of evaluations through EPA’s 

Significant New Alternatives Policy (SNAP)), or published in peer-reviewed scientific journals.

1

 This 

document provides background for EPA’s analysis of the GWP for these compounds. The key 

considerations that EPA took into consideration in the assessment of the GWPs for each compound are 

described in Section 2.0 of this document. The 26 compounds that EPA is proposing to include in Table 

A-1, the proposed GWP for each compound, the origin of the GWP assessment, and the analyses for each 

compound are discussed in sections 3.0 and 4.0 of this document. 

2.0 KEY CONSIDERATIONS IN GWP CALCULATION METHODS 

The GWPs for all GHGs are calculated as the ratio of the time-integrated radiative forcing of a 

one-kg emission of the GHG relative to the time-integrated radiative forcing of a one-kg emission of the 

reference gas (CO2). The GWPs in Table A-1 are calculated based on the effects of the GHGs over a 100-

year time horizon. For both the GHG and the reference gas, the two major inputs to the time-integrated 

radiative forcing are the radiative efficiency of the gas and the concentration of the gas in the atmosphere 

over time. The concentration over time is in turn related to the atmospheric lifetime of the gas. 

The lifetime of a compound is affected by the compound’s reaction rates through reaction with 

atmospheric oxidants (e.g., ozone or hydroxyl radicals) or through photolysis (destruction by light). 

These rates, as well as the radiative efficiency of the compound, depend on reactivity with atmospheric 

oxidants and the distribution of the compound in the atmosphere with altitude, latitude and longitude. 

 

1 The SNAP program is EPA’s program to evaluate substitutes for the ozone-depleting substances that 

are being phased out under the stratospheric ozone protection provisions of the Clean Air Act (as 

implemented in 40 CFR part 82). As part of EPA's assessment of a substitute's overall risk to human 

health and the environment, the EPA reviews scientific assessments of the GWP and considers this, 

among other criteria, in evaluating a substitute.
Radiative efficiency is a measure of the influence a GHG has in altering the balance of incoming solar 

radiation and outgoing infrared radiation in the Earth’s atmosphere when its concentration in the 

atmosphere increases by a particular amount (e.g., by 1 part per billion). The accuracy of the radiative 

efficiency calculation depends on the infrared absorptive properties of the gas and the atmospheric 

concentration and distribution of the gas. The most accurate approach to derive a GWP is to use a full 

three-dimensional model of the global atmosphere. However, alternative estimation approaches have been 

developed and are frequently relied on in scientific assessments of GWP. To determine the proposed 

GWP values for inclusion in Table A-1, EPA reviewed the available literature for each compound and 

evaluated the accuracy of the measurements or modeling methods of these parameters. 

For each compound where EPA identified a scientific assessment, EPA took into consideration the 

methods used to estimate the reactivity and lifetime of the compound, whether the compound is shortlived or long-lived, and whether the scientific assessment made appropriate assumptions in the derivation 

of the radiative efficiency of the compound. Many of the alternative approaches used to estimate GWP 

use simplifying assumptions that are not fully applicable to compounds that are short-lived in the 

atmosphere (defined here as any compound with an atmospheric lifetime less than 1 year). A number of 

GWP assessments rely on the assumption that the compound is well-mixed (i.e., spread evenly over all 

longitudes, latitudes, and altitudes). For example, some studies estimate atmospheric lifetime by assuming 

that the compound is exposed to the global average concentration of hydroxyl radicals (OH), or by 

deriving the lifetime of a compound from the known lifetime of a long-lived (i.e., well-mixed) reference 

compound with similar reaction rates. Short-lived compounds do not last long enough to become wellmixed. Instead, their concentrations decrease rapidly with distance from their emission point, particularly 

with changing latitude and altitude. The assumption that short-lived compounds are well-mixed affects 

both estimates of the atmospheric lifetime and the radiative efficiency. This assumption may overestimate 

the share of the short-lived compounds that resides higher in the atmosphere, where lower temperatures 

and pressures slow reaction rates and lengthen lifetimes. Generally, GHGs which reside higher in the 

atmosphere (i.e, near the tropopause) have longer lifetimes and are responsible for more radiative forcing 
than the same GHGs lower in the atmosphere. Therefore, the assumption that short-lived compounds are 

well-mixed may greatly overestimate the radiative efficiency of these compounds. 

Furthermore, for many compounds, a significant atmospheric sink is oxidation via reaction with 

OH, the most important reactive species in the lower atmosphere. For compounds for which reaction with 

OH is the primary destruction mechanism, the assumption that compounds are well-mixed overestimates 

the share of the compound that makes it to the tropics, where OH concentrations are much higher than at 

the mid-latitudes where the compounds are emitted. Therefore, on balance, the lifetimes of the short-lived 

compounds that react with OH are underestimated by assuming they are well mixed. While assuming that 

the compound is well-mixed can provide reasonable radiative efficiency estimations for long-lived gases, 

the method is less accurate for short-lived gases. The time-integrated radiative forcing (and hence the 

GWP) of short-lived compounds are likely overestimated when the methodology includes an assumption 

that the compound is well-mixed. 

3.0 COMPOUNDS IDENTIFIED FROM PROVISIONAL GWP REQUESTS AND 

SUBMITTED BY SUBPART L PRODUCERS 

EPA is proposing to include 21 F-GHGs with associated GWPs in Table A-1 that were identified 

through provisional GWP requests submitted by subpart L producers, or for which information on the 

GWP was received from subpart L producers. 

Subpart L reporters must use a default GWP unless they submit a request to use provisional 

GWPs for those F-GHGs following the requirements of 40 CFR 98.123(c)(1)(vi). Per 40 CFR 

98.123(c)(1)(vi), reporters must submit data and analysis that supports the estimate of the GWP for the FGHG. EPA identified 11 compounds for inclusion in Table A-1 following receipt of requests for 

provisional GWP analyses from Honeywell International (“Honeywell”) and DuPont de Nemours, Inc. 

(“DuPont”) on February 25, 2011 and February 28, 2011, respectively. The 11 compounds include: seven 

compounds for which EPA approved provisional GWPs for purposes of the calculations in 40 CFR 

98.123(c)(1) on February 24, 2012, and four compounds for which the EPA evaluated the GWPs, but 
not for the purposes of the calculations in 40 CFR 98.123(c). The calculated emission rates of these 

chemicals, when using the default GWP, did not exceed the 10,000 metric tons CO2e threshold and did 

not meet the conditions of 40 CFR 98.123(c)(1)(v). . The fact that EPA did not approve the GWPs for the 

four compounds for the purposes of the calculations in 40 CFR 98.123(c)(1) was not due to disagreement 

with the companies’ suggested GWPs, and EPA is proposing to amend Table A-1 to include these four 

gases. EPA reviewed the scientific assessments of GWP for each compound in the memorandum 

“Supporting Analysis For Mandatory Reporting Of Greenhouse Gases: Notice Of Preliminary 

Determinations Regarding Requests To Use Provisional Global Warming Potentials Under The 

Fluorinated Gas Production Category Of The Greenhouse Gas Reporting Rule.” (see Docket ID No. EPAHQ-OAR-2009-0927-0256). EPA determined that the methods used to estimate the GWPs were likely to 

overestimate the GWPs by an order of magnitude or more. These compounds are all relatively short-lived, 

and the analyses to determine the GWP for these compounds used the simplifying assumptions that the 

compounds are well-mixed in the atmosphere. In general, the assumption that short-lived compounds are 

well-mixed overestimates the radiative forcing of these gases and may affect estimates of the atmospheric 

lifetime. Because of this simplifying assumption, the proposed GWPs are likely to be overestimates. 

On August 21, 2012, DuPont Chambers Works submitted 10 F-GHGs with suggested GWPs and 

supporting data and analysis. For each compound, DuPont included peer-reviewed scientific data 

supporting the suggested GWP. EPA proposes to include these compounds in Table A-1. EPA has 

reviewed the scientific assessments of GWP for each compound. Details of the analysis are included in 

the memorandum “Analysis of proposed GWPs for Table A-1.” Memorandum from Mark Flugge, ICF to 

EPA. September 5, 2012 (see Docket ID No. EPA-HQ-OAR-2012-0934). The radiative efficiency of 

each compound is derived using a constant mixing ratio of the compounds in the troposphere. For four of 

the compounds, the approach used to calculate the atmospheric lifetimes, which assumed that these gases 

were well-mixed, likely underestimates the lifetimes of these compounds. This approach underestimates 

the concentration of O2 and overestimates the concentration of OH to which the compound is actually 

exposed. The overestimate of the OH concentration has a greater effect on the reaction rate and estimated 
lifetime of the compound. However, the radiative efficiency calculation is likely to outweigh the 

underestimated lifetimes. The EPA reviewed recent research that suggests the approach used to determine 

the radiative efficiency for these compounds can result in overestimates of the 100-yr GWP of 49 to 233 

percent (see Wang et al., in draft). Therefore, the GWP estimates for these 10 compounds are likely upper 

bounds. However, because the GWP of each F-GHG is very low (i.e., between 1 and 5), EPA determined 

that the GWPs estimates provided by DuPont would not significantly overestimate source category 

emissions or supply and are acceptable for the purposes of calculating emissions under Part 98. 

Additional details of the analysis are in the memorandum “Analysis of Proposed GWPs for Table A-1.” 

(see Docket ID No. EPA-HQ-OAR-2012-0934). 

In addition to the supporting analyses listed above for the 21 compounds submitted by subpart L 

producers, we identified additional supporting GWP estimates that were published in the Federal Register 

under EPA’s SNAP program (40 CFR part 82) for three compounds. The SNAP program is EPA’s 

program to evaluate substitutes for the ozone-depleting substances that are being phased out under the 

stratospheric ozone protection provisions of the Clean Air Act (as implemented in 40 CFR part 82). As 

part of EPA’s assessment of a substitute’s overall risk to human health and the environment, the EPA 

reviews scientific assessments of the GWP and considers this, among other criteria, in evaluating a 

substitute. EPA also considered these additional GWP estimates when proposing the GWPs for the 

associated compounds in Table A-1. Table 2-1 of this document provides the origin of each compound 

and GWP assessment, proposed GWP, and EPA’s supporting analysis. 

Table 2-1. Proposed Compounds and Associated GWPs for Table A-1 from Provisional GWP 

Requests

Chemical Designation 

or Common Name CAS No. 

Chemical 

Formula 

Propos

ed 

GWP 

Origin of Compound and 

GWP Assessments 

Supporting 

Analysis 

HFC-1234ze(E); HFO1234ze; HFC1234ze(E); HFC1234ze 29118-24-9 CF3CH=CHF 6 Approved as provisional GWP 

for Honeywell Internationala

and published under EPA’s 

SNAP Program (40 CFR part 

82)b

c

hexafluoropropylene; 

PFC-1216 

116-15-4 CF3CF=CF2 0.25 Approved as provisional GWP 

for DuPont de Nemoursa 

c
perfluoromethyl vinyl 

ether (PMVE) 

1187-93-5 C3F6O; 

CF(CF3)OCF3

3 Approved as provisional GWP 

for E. DuPont de Nemoursa

c

tetrafluoroethylene 

(TFE) 

116-14-3 CF2=CF2 0.02 Approved as provisional GWP 

for E. DuPont de Nemoursa

c

trifluoro propene 

(TFP); HFC-1243zf; 

HFO-1243zf 

677-21-4 CF3CH=CH2 3 Approved as provisional GWP 

for E. DuPont de Nemoursa

c

vinyl fluoride (VF); 

HFC-1141 

75-02-5 CHF=CH2 0.7 Approved as provisional GWP 

for E. DuPont de Nemoursa

c

vinylidine Fluoride 

(VF2); HFC-1132a 

75-38-7 CH2=CF2 0.9 Approved as provisional GWP 

for E. DuPont de Nemoursa

c

carbonyl fluoride; 

carbonyl difluoride 

353-50-4 COF2 2 Submitted with provisional 

GWP request for E. DuPont de 

Nemours, no provisional GWP 

approveda 

c

perfluoropropyl vinyl 

ether (PPVE) 

1623-05-8 C5F10O 3 Submitted with provisional 

GWP request for E. DuPont de 

Nemours, no provisional GWP 

approveda

c

perfluoroethyl vinyl 

ether (PEVE) 

10493-43-3 CF3-CF2OC=CF2 3 Submitted with provisional 

GWP request for E. DuPont de 

Nemours, no provisional GWP 

approveda

c

HFO-1234yf; HFC1234yf 754-12-1 CF3CF=CH2 4 Submitted with provisional 

GWP request for Honeywell 

International, no provisional 

GWP approved,a and 

published under EPA’s SNAP 

Program (40 CFR part 82)b

c

perfluorethyl iodide (2-

I) 

354-64-3 C2F5I 3 Submitted by DuPont 

Chambers Works. “Request to 

Use a Provisional GWP for 

(perfluoroethyl) iodide (CAS 

Number 354-63-3).” 

Submitted to Climate Change 

Division, Office of 

Atmospheric Programs, U.S. 

Environmental Protection 

Agency. August 21, 2012. 

d

perfluorbutyl iodide 

(PFBI) 

423-39-2 C4F9I 3 Submitted by DuPont 

Chambers Works. “Request to 

Use a Provisional GWP for 

(perfluoroethyl) iodide (CAS 

Number 354-63-3).” 

Submitted to Climate Change 

Division, Office of 

Atmospheric Programs, U.S. 

Environmental Protection 

Agency. August 21, 2012. 

Published under EPA’s SNAP 

Program (40 CFR part 82)f

d

perfluoro-1-iodohexane; 355-43-1 CF3CF2CF2CF2 2 Submitted by DuPont d
perfluorhexyl iodide (6

-

I) 

CF

2CF2IC6

F13I Chambers Works. “Request to 

Use a Provisional GWP for 

(perfluorohexyl) iodide (CAS 

Number 355-43-1).” 

Submitted to Climate Change 

Division, Office of 

Atmospheric Programs, U.S. 

Environmental Protection 

Agency. August 21, 2012. 

perfluoroctyl iodide (8-

I) 

507-63-1C

8

F17I2 Submitted by DuPont 

Chambers Works. “Request to 

Use a Provisional GWP for 

(perfluorooctyl) iodide (CAS 

Number 507-63-1).” 

Submitted to Climate Change 

Division, Office of 

Atmospheric Programs, U.S. 

Environmental Protection 

Agency. August 21, 2012. 

d

1,1,1,2,2-pentafluoro-

4-iodo butane (22-I) 

40723-80-6C

4

H4F

5

I2 Submitted by DuPont 

Chambers Works. “Request to 

Use a Provisional GWP for 

1,1,1,2,2-pentafluoro-4-iodo 

butane (CAS Number 40723-

80-6).” Submitted to Climate 

Change Division, Office of 

Atmospheric Programs, U.S. 

Environmental Protection 

Agency. August 21, 2012. 

d

1,1,1,2,2,3,3,4,4-

nonafluoro-6-iodo 

hexane (42-I) 

2043-55-22 Submitted by DuPont 

Chambers Works. “Request to 

Use a Provisional GWP for 

1,1,1,2,2,3,3,4,4-nonafluoro-6-

iodo hexane (CAS Number 

2043-55-2).” Submitted to 

Climate Change Division, 

Office of Atmospheric 

Programs, U.S. Environmental 

Protection Agency. August 21, 

2012. 

d

perfluorobutyl ethylene, 

perfluorobutyl ethene 

(42-U) 

19430-93-4C

6

H

3

F

9

2 Submitted by DuPont 

Chambers Works. “Request to 

Use a Provisional GWP for 

(perfluorobutyl) ethene (CAS 

Number 19430-93-4).” 

Submitted to Climate Change 

Division, Office of 

Atmospheric Programs, U.S. 

Environmental Protection 

Agency. August 21, 2012. 

d,e

perfluorohexyl 

ethylene, 

perfluorohexyl ethene 

(62-U) 

25291-17-2C

8

H

3

F13; 

CH

2=CH(CF2

C

F

2

)

3F 

1 Submitted by DuPont 

Chambers Works. “Request to 

Use a Provisional GWP for 

(perfluorohexyl) ethylene 

(CAS Number 25291-17-2).” 

Submitted to Climate Change 

d,e
Division, Office of 

Atmospheric Programs, U.S. 

Environmental Protection 

Agency. August 21, 2012. 

perfluorooctyl ethane 

(82-U); perfluorooctyl 

ethylene 

21652-58-4 C10H3F17 1 Submitted by DuPont 

Chambers Works. “Request to 

Use a Provisional GWP for 

(perfluorooctyl) ethene (CAS 

Number 21652-58-4).” 

Submitted to Climate Change 

Division, Office of 

Atmospheric Programs, U.S. 

Environmental Protection 

Agency. August 21, 2012. 

d,e

1H,1H, 2H,2Hperfluorohexan-1-ol 

(42-AL) 

2043-47-2 C6H5F9O 5 Submitted by DuPont 

Chambers Works. “Request to 

Use a Provisional GWP for 

1H,1H, 2H,2Hperfluorohexan-1-ol (CAS 

Number 2043-47-2).” 

Submitted to Climate Change 

Division, Office of 

Atmospheric Programs, U.S. 

Environmental Protection 

Agency. August 21, 2012. 

d,e

a

 See “Mandatory Reporting of Greenhouse Gases: Notice of Preliminary Determinations Regarding Requests to 

Use Provisional Global Warming Potentials Under the Fluorinated Gas Production Category of the Greenhouse Gas 

Reporting Rule” (77 FR 5514, February 3, 2012). 

b For CF3CH=CHF and CF3CF=CH2, the GWP and atmospheric lifetime estimates published under the SNAP 

program support the provisional GWPs. 

c

 See “Supporting Analysis For Mandatory Reporting Of Greenhouse Gases: Notice Of Preliminary Determinations

Regarding Requests To Use Provisional Global Warming Potentials Under The Fluorinated Gas Production 

Category Of The Greenhouse Gas Reporting Rule. Office of Air and Radiation, U.S. Environmental Protection 

Agency. January 24, 2011; Docket ID No. EPA-HQ-OAR-2009-0927-0256. 

d

 See “Analysis of proposed GWPs for Table A-1.” Memorandum from Mark Flugge, ICF to EPA. September 5, 

2012; Docket ID No. EPA-HQ-OAR-2012-0934 

e

 For the compounds perfluorobutyl ethene, perfluorohexyl ethene, perfluorooctyl ethene, and 1H,1H,2H,2Hperfluorohexan-1-ol, the lifetimes of each F-GHG are estimated using kinetic reaction rates for reaction with 

common atmospheric oxidants (OH and/or ozone (O3)), using global weighted-average concentrations of each 

oxidant. Overall, this assumption overestimates the reaction rates of these gases and likely underestimates the

lifetimes. The methods used underestimate the concentration of O3 and overestimate the concentration of OH to 

which the compound is actually exposed. The overestimate of the OH concentration has a greater effect on the 

reaction rate and estimated lifetime of the compound. 

f For perfluorbutyl iodide (PFBI), the GWP and atmospheric lifetime estimates published under the SNAP program 

are less than 5 and a few days, respectively. 

4.0 COMPOUNDS IDENTIFIED FROM PEER-REVIEWED SCIENTIFIC 

ASSESSMENTS OR OTHER EPA RULEMAKINGS 

EPA is also proposing to amend Table A-1 to include five F-GHGs which were identified from 

EPA’s review of industrial gases produced for or used in the electronics manufacturing, fluorinated gas 
production, and magnesium production source categories and for which scientific assessments of GWP 

have been published under EPA’s SNAP program or identified in peer reviewed literature. The origin of 

each compound and GWP assessment are identified in Table 2-2 of this document. EPA’s analyses of the 

available GWP estimates are discussed in Sections 2.2.1 through 2.2.4 of this document. 

Table 2-2. Proposed Compounds and Associated GWPs for Table A-1 from Other Rulemakings or 

Peer-Reviewed Scientific Assessments 

Chemical Designation or 

Common Name CAS No. Chemical Formula 

Proposed 

GWP 

Origin of Compound and GWP 

Assessments 

trans-1-chloro-3,3,3-

trifluoroprop-1-ene 

102687-65-0 CF3CH=CHCl 7 Published under EPA’s SNAP 

Program (40 CFR part 82) and 

identified in peer reviewed 

literature 

FK-5-1-12; C6 

perfluoroketone; FK–5–

1–12myy2; nperfluorooctane; 

octanedecafluorooctane 

756-13-8 CF3CF2C(O)CF(C

F3)2

1.8 Published under EPA’s SNAP 

Program (40 CFR part 82) and 

identified in manufacturer’s 

literature 

C7 fluoroketone, Novec 

774/FK-6-1-12 

813-44-5 and 

813-45-6 

Blend of two 

isomers: 3- 

pentanone,1,1,1,2,4

,5,5,5- 

octafluoro-2,4- 

bis(trifluoromethyl

) and 3- 

hexanone,1,1,1,2,4,

4,5,5,6,6,6- 

undecafluoro-2-

(trifluoromethyl) 

1 Published under EPA’s SNAP 

Program (40 CFR part 82) 

PFC-6-1-12; 

hexadecafluoroheptane 

335-57-9 C7F16 7930 Identified in peer reviewed 

literature 

PFC-7-1-18; 

octadecafluorooctane 

307-34-6 C8F18 8340 Identified in peer reviewed 

literature 

4.1 trans-1-chloro-3,3,3-trifluoroprop-1-ene

An analysis of the GWP of trans-1-chloro-3,3,3-trifluoroprop-1-ene (trade name SolsticeTM 123 

3zd(E)) was previously performed through EPA’s SNAP Program (See “Protection of Stratospheric 

Ozone: Determination 27 for Significant New Alternatives Policy Program,” Docket Id. No. EPA-HQOAR-2003-0118). As part of the SNAP analysis, EPA evaluated two recent studies estimating the GWP 

for trans-1-chloro-3,3,3-trifluoroprop-1-ene, and estimated a GWP between 4.7 and 7. Andersen et al. 
(2008) estimated a GWP of 7 for this compound. Andersen et al. measured the kinetic reaction rate of 

trans-1-chloro-3,3,3-trifluoroprop-1-ene with common oxidants OH, O3, and chlorine (Cl) to establish 

atmospheric lifetime, using global weighted-average concentrations of each oxidant. The use of global 

weight-average concentrations assumes that the short-lived gas is well-mixed. To calculate the radiative 

efficiency of the compound, Andersen et al. (2008) measured infrared spectra using Fourier Transform 

Infrared (FTIR) spectroscopy and the estimation methods in Pinnock et al. (1995). The methods assume 

that trans-1-chloro-3,3,3-trifluoroprop-1-ene is well-mixed in the atmosphere. As a result, the GWP 

calculated by Andersen et al. is likely overestimated. The SNAP analysis also provided a GWP estimate 

for trans-1-chloro-3,3,3-trifluoroprop-1-ene) of 4.7 from an unpublished study (see 77 FR 47770, August 

10, 2012). 

EPA also considered an unpublished paper by Wang et al. (in draft) which re-evaluates the 

atmospheric lifetime of trans-1-chloro-3,3,3-trifluoroprop-1-ene using a three-dimensional chemical 

transport model, which provides temporal and spatial concentrations that can be used to simulate mixing 

ratios. The simulated mixing ratios are used to recalculate the radiative efficiency. The model used by 

Wang et al. (in draft) may provide a more accurate estimate of both atmospheric lifetime and forcing for 

short-lived compounds, because it does not rely on the assumption that these compounds are evenly 

distributed in the atmosphere. Wang et al. (in draft) calculates a lifetime of 31 days for trans-1-chloro3,3,3-trifluoroprop-1-ene and estimates a GWP of 4.7. Although the Wang et al. studies cited give a 

GWP of 4.7 for trans-1-chloro-3,3,3-trifluoroprop-1-ene, EPA believes it is more appropriate to use the 

GWP from the Andersen et al. study, as it comes from a peer-reviewed journal article. Also, consistent 

with the reasoning for choosing possibly upper-bound GWPs for other chemicals in Table 3 of this 

preamble, using the GWP of 7 rather than 4.7 would not significantly overestimate source category 

emissions. 

4.2 FK-5-1-12 
The compound FK-5-1-12 (1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluoromethyl)-3-pentanone,also 

produced under the trade names NovecTM 612 and NovecTM 1230) is a fluorinated ketone. Product 

information provided by the manufacturer provides a GWP estimate of 1 for a 100-year integration using 

IPCC 2007 calculation methods (3M Company, 2009). However, an analysis of the GWP of FK-5-1-12 

(identified in the analysis as Novec 1230) was previously performed through EPA’s SNAP Program (See 

“Protection of Stratospheric Ozone: Listing of Substitutes for Ozone Depleting Substances, Correction” 

(68 FR 16729, April 7, 2003)). The SNAP analysis is based on a review of Taniguchi et al. (2003), which 

examines the reaction of FK-5-1-12 in the atmosphere and associated reaction products. The study 

concludes that the atmospheric lifetime of FK-5-1-12 is one to two weeks, and suggests that products of 

the reaction would contribute additional CO2 to the atmosphere. The SNAP analysis re-evaluates the

GWP of FK-5-1-12 for a 100-year integration, using the IPCC approach. The GWP accounts for indirect 

effects, including the rainout of the reaction product CHF3COF, and has been further revised and 

evaluated to account for mass. The total GWP is comprised of a direct value of less than 1 but greater 

than zero, plus an indirect GWP of 0.56 to 0.84, based on 4 to 6 carbons available (from 

photodissociation) for conversion to CO2. Multiplying the calculated GWPs by the ratio of CO2 mass to 

C-6 oxyfluorocarbon mass results in a 100 year GWP for FK-5-1-12 between 0.6 and 1.8. EPA is 

currently proposing a GWP of 1.8. The methods used to evaluate radiative forcing for FK-5-1-12 assumed 

a constant mixing ratio for the compound, which likely overestimates the time-integrated radiative forcing 

and the GWP. However, because the proposed GWP of the compound is so low, the proposed value 

would not likely result in substantial over-reporting for the magnesium production source category. See 

“Protection of Stratospheric Ozone: Listing of Substitutes for Ozone Depleting Substances, Correction” 

(68 FR 16729, April 7, 2003) and Docket Id. No. EPA-HQ-OAR-2003-0118-0049 for the EPA’s full 

analysis of the GWP of FK-5-1-12. 

4.3 FK-6-1-12 
The compound FK-6-1-12 (C7 fluoroketone, also produced under the trade name NovecTM 774), 

is a blend of two isomers: 3- pentanone,1,1,1,2,4,5,5,5-octafluoro-2,4-bis(trifluoromethyl) and 3- 

hexanone,1,1,1,2,4,4,5,5,6,6,6-undecafluoro-2-(trifluoromethyl). The GWP of FK-6-1-2 was previously 

published under EPA’s SNAP Program (See “Protection of Stratospheric Ozone: Determination 27 for 

Significant New Alternatives Policy Program,” Docket Id. No. EPA-HQ-OAR-2003-0118). Although the 

estimation methods for the GWP were considered confidential business information, the SNAP analysis 

provides a 100-year integrated GWP of 1. The compound also has a chemical structure similar to that of 

FK-5-1-12, therefore, we would anticipate a similar lifetime and GWP for these compounds. 

4.4 C7F16 and C8F18

There are no previous estimates of the GWP of the perfluorocarbons (PFCs) C7F16 and C8F18. 

EPA identified Ivy et al. (2012), a recent study that provides global emission estimates of each PFC using 

a three-dimensional chemical transport model and infrared spectra measurements to determine the GWP 

of these PFCs. The infrared spectra of each compound was measured using FTIR spectroscopy., The 

authors assumed an atmospheric lifetime of 3,000 years for each gas based on previous lifetime estimates 

for chemically-similar compounds. The radiative efficiency of each compound was calculated using the 

measured infrared spectra and the methods in Pinnock et al. (1995). These compounds are long-lived 

gases that are expected to be well-mixed in the atmosphere. Because the expected lifetimes of these PFCs 

are much longer than the 100-year timeline used as the basis of the GWP, they are relatively insensitive to 

the assumed lifetime. Furthermore, the methods and assumptions used by Ivy et al. (2012) are generally 

considered reliable for long-lived gases. Therefore, we recommend GWPs of 7930 and 8340 for C7F16 and 

C8F18, respectively, as presented by Ivy et al. 
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Atmospheric Ozone.” Department of Atmospheric Sciences. University of Illinois, Urbana, 

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Wang D., Wuebbles D., Patten K., and Olsen, S. Undated. Climate advantages of proposed short-lived 

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