Title: Climate advantages of proposed short-lived compounds as replacements 

for longer-lived HCFCs and HFCs 

Authors: Dong Wang,1 Donald J. Wuebbles,1* Kenneth O. Patten,1 Seth C. Olsen1 

Affiliations: 

1Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, Urbana, 

Illinois, USA. 

*Correspondence to: wuebbles@illinois.edu 

Abstract: Many of the halocarbons currently used as refrigerants, blowing agents, etc., are of 

environmental concern because they are sufficiently long-lived to affect climate. In this study, 

we not only examine the atmospheric lifetimes and Global Warming Potentials (GWPs) for six 

short-lived potential replacement hydrocarbons, but also evaluate the potential reduced effects on 

climate forcing from using such compounds. The atmospheric lifetimes of these compounds are 

each less than one month and their 100-yr GWPs range from 0.9 to 4.7. The derived GWPs are 

substantially lower than those in prior published studies using simplified estimation techniques 

that overestimate the GWPs for these short lived compounds by 49% to 233%. If long-lived 

HFCs are completely replaced with these substitute compounds, radiative forcing of these shortlived compounds in 2050 will be 0.26 to 0.80 mW m-2, substantially smaller than that of HFCs 

(0.25 to 0.40 W m-2). 

Main Text: The halocarbons currently used as refrigerants, blowing agents, etc., are not only 

greenhouse gases, but are sufficiently long-lived to have meaningful effects on climate. For 

major applications ranging from refrigerants to foam blowing agents, HFCs are currently the 

primary substitutes to chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), 

substances listed as Ozone-Depleting Substances (ODSs) in the Montreal Protocol, mainly 

(IPCC/TEAP, 2005). Because they have atmospheric lifetimes of several years and absorb 

radiation in the window region at infrared wavelengths, many HFCs are more than 100 times 

more powerful than CO2 in terms of radiative forcing on a per-mass basis in the atmosphere 

(IPCC, 2007). The current radiative forcing of HFCs is small (0.012 Wm-2 in 2010), however, 

radiative forcing of HFCs can be as much as 0.25 to 0.40 Wm-2 in 2050, according to recently 

developed estimates for continued growth in the use of these compounds (Velders et al., 2009). 

Recently, various unsaturated halogenated hydrocarbons with very short atmospheric 

lifetimes have been proposed as substitutes for HCFCs (now being phased out under the 

Montreal Protocol) and longer-lived HFCs. These short-lived substances are expected to have 

small, essentially negligible, effects on atmospheric ozone and on climate. The chemical 

compounds include trans-1-chloro-3,3,3-trifluoropropylene (trans-CF3CH=CHCl, or tCFP for 

short), and five hydrofluoro-olefins (HFOs): 2,3,3,3-tetrafluoropropene (CF3-CF=CH2, or HFO1234yf), trans-1,3,3,3-tetrafluoropropene (trans-CHF=CH-CF3, or HFO-1234ze(E)), cis-1,3,3,3-

tetrafluoropropene (cis-CHF=CH-CF3, or HFO-1234ze(Z)), cis-1,2,3,3,3-pentafluoropropene 

(cis-CF3-CF=CHF, or HFO-1225ye(Z)), and trans-1,2,3,3,3-pentafluoropropene (trans-CF3-

CF=CHF, or HFO-1225ye(E)). HFO-1234yf can serve as a mobile air conditioning refrigerant; 

HFO-1234ze(E) can work as a blowing agent and propellant; tCFP can serve as a blowing agent; 

HFO-1234ze(Z) has been suggested as a refrigerant (Brown et al., 2009); HFO-1225ye(Z) and -

1225ye(E) have been also proposed as refrigerants (Hurley et al., 2007). The prospect of using 
HFO-1234yf and HFO-1234ze(E) has been discussed in the literature (UNEP, 2011; Velders et 

al., 2012). 

It is well established that the C=C bonds (Carbon-Carbon double bonds) are more prone 

than C-C or C-H bonds to react with the hydroxyl radical (OH) in the atmosphere (e.g., Atkinson 

et al., 2005). Therefore, these six compounds, all of which contain C=C bonds, typically have 

shorter lifetimes than those saturated compounds with similar molecular formulae. Laboratory 

chemical kinetics studies suggest that the reaction with OH is virtually the single degradation 

pathway of these compounds. The atmospheric lifetimes of all of these compounds are estimated 

to be less than one month (Table 1; Eq. S1) tCFP (Sulbaek Anderson et al., 2008), HFO-1234yf 

(Nielsen et al., 2007), HFO-1234ze(E) (Sondergaard et al., 2007), HFO-1234ze(Z) (Nilsson et 

al., 2009), HFO-1225ye(Z) (Hurley et al., 2007), and HFO-1225ye(E) (Hurley et al., 2007). 

Assuming constant mixing ratio profiles throughout the atmosphere (troposphere and 

stratosphere), Global Warming Potentials (GWPs) over 20- and 100-year horizons were derived 

in these papers following the simple estimation approach of Pinnock et al. (1995) (supporting 

material). The 100-yr GWPs derived this way are all less than 10 (Table 2). Patten and Wuebbles 

(2010) suggested that tCFP, the only compound containing Cl atoms among these six 

compounds, has negligible effect on ozone in the atmosphere (Ozone Depletion Potential (ODP) 

less than 0.001). The other five compounds, comprising of carbon, hydrogen, and fluorine atoms, 

have essentially no impact on atmospheric ozone. With such low GWPs and ODPs, these six 

unsaturated halogenated hydrocarbons have the potential to constitute a new generation of 

compounds that are friendly both to the ozone layer and to climate. 

However, previous studies (Hurley et al., 2007; Nielsen et al., 2007; Nilsson et al., 2009; 

Sondergaard et al., 2007; Sulbaek Anderson et al., 2008) use inaccurate approximations in 

deriving the lifetimes and radiative forcing for these short-lived substances. In those studies, 

atmospheric lifetimes are estimated using essentially a box model, either assuming a global 

weighted-average OH concentration, or scaling to methyl chloroform lifetime. As discussed 

below, neither method is adequate for very short-lived compounds. In addition, the radiative 

forcing for the compounds were calculated assuming constant mixing ratios throughout the 

atmosphere. While these methods have been common practice and proved to be reasonable for 

long-lived halocarbons, they are not accurate for short-lived compounds. 

Atmospheric mixing ratios for short-lived compounds are known to vary significantly 

with latitude and altitude (e.g., Olsen et al., 2000; Wuebbles et al., 2001; Wuebbles et al., 2009). 

Previous studies have shown that vertically dependent profiles of gases are important in 

evaluating their potential radiative forcing (e.g., Jain et al., 2000). In this study, temporally and 

spatially varying concentrations of the six species are obtained assuming a regional-dependent 

emission pattern (based on current primary and likely application needs) using the WACCM 

(Whole Atmosphere Community Climate Model ) three-dimensional global climate-chemistry 

model, in order to derive their atmospheric lifetimes. The simulated mixing ratio profiles are 

used in a narrow band radiative transfer model to calculate their radiative forcing. Global 

Warming Potentials (GWPs) are then derived for each compound. 

WACCM is a three-dimensional global atmospheric climate-chemistry model developed 

by the National Center for Atmospheric Research (NCAR) (e.g., Calvo et al., 2011; Garcia et al., 

2011; Patten et al., 2011). WACCM has been evaluated and used in a number of scientific 

studies, for example, in the Stratospheric Processes And their Role in Climate (SPARC) 2010 

Report (Eyring et al., 2010). The model performs well in simulating the stratosphere and the 
upper troposphere and lower stratosphere as shown in the Chemistry-Climate Model Validation 

Activity (CCMVal) (Eyring et al., 2010; Gettelman et al., 2010). WACCM version 3.5.48 is used 

in this study to derive the steady-state concentration profiles and atmospheric lifetimes for the 

very short-lived species. The model numerically simulates the atmosphere from the surface up to 

the 4.5 ×10-4 Pa level (~145km). The model is run in offline mode, that is, the meteorological 

fields are driven by a meteorological dataset obtained from a previous WACCM run 

approximating the current atmosphere; after one year’s simulation is complete, and the 

meteorological dataset is repeated again. The model simulates 125 chemical species and uses the 

JPL06 recommendations on chemical reactions in the atmosphere (Sander et al., 2006) including 

representation of non-methane hydrocarbon chemistry, which is important to a good 

representation of tropospheric oxidative capacity. Surface concentrations of long-lived gases 

(e.g., CO2, CH4, and N2O) are all fixed for the year 2004. 

For each of the compounds, the rate constants used for reaction with OH are summarized 

in Table 1. To have a realistic, statistically-significant representation of the geographical and 

altitude distribution of these compounds, we assume a global emission of 15.6 Tg/yr, distributed 

proportional to blowing agents consumption in the year 2010 (Rajiv Singh, private 

communication, 2011). The annual emissions of each compound are 3.4, 0.6, 4.8, 0.9, 0.5, 0.9, 

1.6, and 2.7 Tg in the regions of the European Union, Japan, China, India, Turkey, the Middle 

East and North Africa, Latin America, and North America, respectively. The basis of doing this 

is that consumption is proportional to regional population and GDP (IPCC, 2000). We assume 

that emissions are uniform within each region, and constant throughout the year. The WACCM 

model is run for five years until the key species reach steady state. Concentrations profiles and 

lifetime evaluation are based on analysis of the fifth year’s WACCM output. 

The simulated monthly averaged three-dimensional mixing ratio profiles are input into 

the UIUC Radiative Transfer Model (UIUC RTM; Jain et al., 2000; Naik et al., 2000; Youn et 

al., 2009; Patten et al., 2011), in order to evaluate the radiative forcing of these proposed 

compounds. Shortwave (solar) and longwave (terrestrial) radiation across atmospheric layers is 

calculated in the UIUC RTM. The shortwave spectrum is divided into 18 bins between 0.2 and 

5.0 microns and takes into account the absorption effects of H2O, O3, O2, CO2, clouds and the 

surface, as well as scattering processes of clouds, gas-phase molecules, and the surface. Within 

the UIUC RTM, a narrow band terrestrial radiation (wave number between 0 and 3000 cm-1) 

model calculates absorptivity and emissivity for O3, CH4 CO2, and N2O at 10 cm-1 resolution, 

and for H2O, CFC-11 and CFC-12 at 5 cm-1 resolution. Infrared spectra for these gases are from 

the HITRAN 2004 database, described in Rothman et al. (2005). Clouds, surface albedo, and 

surface emissivity are based on observation from the International Satellite Cloud Climatology 

Project. Infrared spectra data for tCFP, HFO-1234yf, HFO-1234ze(E), HFO-1234ze(Z), HFO1225ye(Z) and HFO-1225ye(E) are reported respectively in Sulbaek Anderson et al. (2008), 

Nielsen et al. (2007), Sondergaard et al. (2007), Nilsson et al. (2009), Hurley et al. (2007) and 

Hurley et al. (2007) are regridded to 10 cm-1 resolution and used in this study. 

Table 1 lists the lifetimes for these compounds calculated from the WACCM model 

results using Eq. S4. Among these six unsaturated halogenated hydrocarbons, HFO-1225ye(E) 

has the shortest lifetime of 9.2 days, while tCFP has the longest lifetime of 30.5 days. With 

lifetimes much shorter than six months, these compounds fall well into the category of very 

short-lived substances (VSLS) (WMO, 2007). Most are degraded before being transported to 

remote regions resulting in very inhomogeneous distributions. Fig. 1 shows the WACCM 
simulated steady-state annual mean zonal average mixing ratios. For each compound, the largest 

mixing ratios are near surface in the northern mid-latitudes, where human activity is most 

intensive and emissions are strongest. Mixing ratios decrease rapidly with distance away from 

location of emissions because of their short lifetime. The longer its lifetime, the further the 

compound can be transported to remote regions. For the assumed emissions scenario, mixing 

ratios of tCFP can reach more than 100 ppt in the northern mid- and high-latitudes below 8 km 

altitude, whereas 100 ppt HFO-1225ye(E) mixing ratio contour does not exceed 3 km altitude. 

Table 1 also gives the lifetimes for these VSLS reported in the literature, calculated using 

the estimation approach by substituting the rate constant of the reaction X + OH obtained in 

laboratories and assuming a constant global weighted-average OH concentration into Eq. S1. As 

OH concentrations in the atmosphere are highly variable, it does not make sense to use a 

globally-averaged OH concentration for such short-lived compounds; as will be shown in the 

coming discussion, the appropriate average would be species and emissions scenario dependent. 

A global weighted-average OH concentration of 1.0×10

6

 molecules cm-3 were used for HFO1234yf, HFO-1234ze(E), HFO-1234ze(Z), and tCFP (Nielsen et al., 2007; Nilsson et al., 2009; 

Sondergaard et al., 2007; Sulbaek Anderson et al., 2008). Whereas for HFO-1225ye(E) and 

HFO-1225ye(Z), their lifetimes were scaled with that of CH3CCl3, whose lifetime is 6.1 years 

and the rate constant for its reaction with OH is 1.0×10-14 cm3

 molecules-1 s-1 (Hurley et al., 

2007). This scaling is equivalent to assuming a global weighted-average OH concentration of 

5.2×105 molecules cm-3. Compared with the lifetimes derived from the 3-D atmospheric model 

simulations in this study, using the estimation approach with a global weighted-average OH 

concentration of 1.0×106 molecules cm-3 leads to an underestimation of atmospheric lifetimes by 

30%, 19%, 30%, and 15% for HFO-1234yf, HFO-1234ze(E), HFO-1234ze(Z), and tCFP, 

respectively; using a global weighted-average OH concentration of 5.2×105

 molecules cm-3, the 

estimation approach results in an overestimation of atmospheric lifetimes by 29% and 9% for 

HFO-1225ye(Z) and HFO-1225(E), respectively (Table 1). 

For the model derived OH distribution, the appropriate average OH concentrations, using 

the estimation approach, to derive the lifetimes the same as those derived from 3-D model 

simulations are also listed in Table 1; these values are compound-dependent and range from 5.9 

to 8.6 ×105 molecules cm-3. The longer the atmospheric lifetime of a compound, the larger the 

corresponding global weighted-average OH concentration. This is because a larger fraction of a 

compound with longer lifetime can be transported to the regions rich in OH, i.e. low latitudes, 

from mid-latitudes where majority of the compound is emitted. The discussion suggests that a 

universal global weighted-average OH concentration for VSLS does not exist, hence assuming a 

global average OH concentration, as in the estimation approach, is not appropriate. 

The Global Warming Potential (GWP) is defined as the ratio of time-integrated radiative 

forcing over a select time horizon after a pulse emission of gas X to that after a pulse emission of 

CO2 of the same mass (IPCC, 1990). The time-integrated forcing for each gas is also called 

absolute GWP, or AGWP. For a VSLS, both the AGWP and radiative forcing caused by 

sustained emission of the strength one unit mass per unit time can be approximated to the 

product of Fand its atmospheric lifetime (see supplementary material for derivation), which is 

readily calculated in the radiative transfer model and are listed in Table 2. GWPs over 20-, 100-, 

and 500-yr horizons for the six unsaturated halogenated hydrocarbons derived from the 3-D 

model method are listed in Table 2. Previous estimates of the 100-yr GWPs based on simplified 

assumptions overestimate the full calculations by 49% to 233%. 
For HFO-1225ye(Z) and HFO-1225(E), the 233% overestimation of their 100-yr GWPs 

using the estimation approach is a combined effect of their overestimated lifetimes and 

overestimated radiative efficiency assuming constant concentration profiles; for the other four 

compounds, even though the overestimation in radiative efficiency is partly offset by the 

underestimation of their lifetime, the overall effect is still an overestimation of 100-yr GWPs by 

more than 49%. 

In order to estimate how much of the GWP differences come from the different radiative 

transfer models used, we carry out experimental RTM simulations in which the WACCM 

calculated VSLS burden in the atmosphere is homogeneously distributed in the atmosphere (i.e., 

constant mixing ratios in the troposphere and stratosphere). The resulting radiative forcing 

changes on a per ppb basis are listed in Table S1, and compared with those reported in the 

previous studies. The differences are within 11%, confirming that the differences in derived 

GWPs come primarily from differences in assumed mixing ratio profiles and atmospheric 

lifetimes. 

This study suggests that the 100-yr GWPs for these very short-lived unsaturated 

halogenated hydrocarbons are all less than 5. Scenarios of replacing HFCs with the low-GWP 

alternative are developed based on the needs for such compounds put together by Velders et al. 

(2009) with the assumptions that (i) productions and consumptions of HFCs decrease linearly 

starting in 2015; (ii) productions and consumptions of HFC-32, -125, -143a, -245fa, and -365mfc 

decrease to zero in 2035; (iii) productions and consumptions of HFC-134a decrease to zero in 

2025; (iv) the demands for refrigerants from use of HFC-32, -125, -134a, and -143a are replaced 

by HFO-1234yf, -1234ze(Z), -1225ye(Z), or -1225ye(E); (v) the demands for blowing agents 

from use of HFC-152a, -245fa, and -365mfc are replaced by HFO-1234ze(E), or tCFP. With 

these assumptions, the radiative forcing of the low-GWP alternatives in 2050 is between 0.26 

and 0.80 mW m-2 (Fig. 2). As a result, radiative forcing from future needs for refrigerants, etc. is 

significantly reduced. In contrast to the monotonically increasing radiative forcing of long-lived 

HFCs that reaches 0.25 to 0.40 W m-2 in 2050, radiative forcing of long-lived HFCs peaks at 

46.3 to 53.5 mW m-2 near 2030 and decreases to 26.1 to 31.3 mW m-2 in 2050. The resulting 

saving in radiative forcing on climate in 2030 is between 0.04 and 0.07 W m-2, comparable to the 

savings of the regulatory black carbon reduction measures, or a sizable fraction of the savings of 

the technological black carbon reduction measures and CH4 reduction measures recently 

suggested by Shindell et al. (2012). 

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Fig. 1. Annual-averaged zonal mean mixing ratios (in ppt by volume) for each of the six 

unsaturated halogenated hydrocarbons calculated by the WACCM model. 

 
Fig. 2. Range of radiative forcing of HFCs in the Velders scenario (red), and radiative forcing of 

low-GWP alternatives (green) and HFCs (blue) in the low-GWP replacement scenario as 

described in the main text. 

 
Table 1. Rate constants for the reactions of the six unsaturated halogenated hydrocarbons and hydroxyl radical (OH). Temperature 

dependence of the reaction rate is not considered in this study based on these laboratory studies. Atmospheric lifetimes for the six unsaturated halogenated hydrocarbons derived from the 3-D model method, and from the estimation approach and percent difference of the estimation approach. OH concentration in order to derive the same lifetimes as do the 3-D method for each gas. 

compound 

rate constant 

(cm

3 molecules-1

s

-1) 

reference 

3-D model method the estimation approach 

NOH to derive same lifetime as 

those from the 3-D model 

method (10

5 molecules cm-3 lifetime (days) ) lifetime (days) % diff. 

HFO-1234yf (1.05±0.17)×10

- 12 Nielsen et al. (2007) 15.7 11 -30% 7.0 

HFO-1234ze(E) (9.25±1.72)×10

- 13 Sondergaard et al. (2007) 17.3 14 -19% 7.2 

HFO-1234ze(Z) (1.20±0.14)×10

- 12 Nilsson et al. (2009) 14.2 10 -30% 6.8 

HFO-1225ye(Z) (1.22±0.14)×10

- 12 Hurley et al. (2007) 14.0 18 +29% 6.8 

HFO-1225ye(E) (2.15±0.23)×10

- 12 Hurley et al. (2007) 9.2 10 +9% 5.9 

tCFP (4.40±0.38)×10

- 13 Sulbaek Andersen et al. 

(2008) 

30.5 26 -15% 8.6 
Table 2. Steady state radiative forcing due to sustained 15.6 Tg/yr emission for each of the six unsaturated halogenated hydrocarbons 

and their AGWPs. GWPs over 20-, 100-, and 500-yr horizons for the six unsaturated halogenated hydrocarbons derived from the 3-D 

model method used in this study, and GWPs over 20- and 100-yr horizons from the estimation approach and errors of the estimation 

approach. 

compound 

3-D model method The estimation approach 

RF 

(mW m-2)

AGWP 

(10-13 W yr m-2 kg-1) 20-yr 100-yr 500-yr 20-yr 20-yr % diff. 100-yr 100-yr % diff.

HFO-1234yf 2.72 1.75 7.4 2.1 0.6 12 +62% 4 +90% 

HFO-1234ze(E) 3.94 2.53 10.2 2.9 0.9 19 +86% 6 +107% 

HFO-1234ze(Z) 2.27 1.46 5.9 1.7 0.5 10 +69% 3 +76% 

HFO-1225ye(Z) 2.40 1.54 6.2 1.8 0.5 21 +239% 6 +233% HFO-1225ye(E) 1.28 0.82 3.3 0.9 0.3 11 +233% 3 +233% 

tCFP 6.27 4.03 16.3 4.7 1.4 26 +60% 7 +49% 
Supplementary Materials: 

Materials and Methods: 

Lifetime estimation approach

τ = 	



	



 (S1) 

where NOH is global weighted-average OH concentration. 

GWP estimation approach in Pinnock et al. (1995) 

In the previous studies the GWPs for these VSLS are estimated through the Halocarbon 

Global Warming Potential (HGWP), over time horizon t defined as the ratio of the GWP for 

gas X to that for CFC-11 

GWP

t = HGWPt × GWPt (S2) 

HGWPt for gas X is obtained by 

HGWPt =  	



	 

 	

 !"#	$⁄	

!"#	$⁄

 (S3) 

where M, M,	 τ, τ, IF, and IF are the molecular weights, 

atmospheric lifetimes, and instantaneous forcings for gas X and CFC-11, respectively. Note in 

the estimation approach the instantaneous forcings for the VSLS are calculated following 

Pinnock et al. (1995) assuming constant mixing ratios in the atmosphere. 

Lifetime calculation from 3-D model output 

The atmospheric lifetime (τ) of a gas X is determined as the ratio of its burden X in the 

atmosphere over the total sink of X. Lifetime can be calculated by integrating its burden and sink 

throughout the whole atmosphere, as shown in Eq.S4 

τ = 	

∫∫[],,-
,,-./.$

∫∫ 	
[],,-[0],,-
,,-

1./.$

 (S4) 

Where k30 is the rate constant of the reaction of X and OH, [X]/,$, [OH]/,$, and N/,$

the mixing ratios of X and OH and number of air molecules per unit volume, respectively, in the 

volume element of interest (V) at time t. 

Eq.S1 is a simplified form of Eq.S4 if k30 is not dependent on temperature, [X] is 

nearly constant throughout the atmosphere, and 

789 =

∫∫[0],,-
,,-

1./.$

∫∫ 
,,-./.$

 (S5) 

However, [X] is highly variable in the atmosphere for very short-lived substances. 

Therefore, Eq.S1 is inadequate to calculate atmospheric lifetimes for very short-lived. 
AGWP and radiative forcing caused by sustained emission 

It is well established that atmospheric concentration of a gas, whose sink is dependent on 

its concentration to the first order, will decay exponentially after emission into the atmosphere 

(except for CO2, which is more complicated). Accordingly, for a gas X whose efficiency in 

changing radiative forcing is proportional to its mass in the atmosphere, the radiative forcing 

caused by a pulse emission of one unit mass X, decays exponentially following 

RF#

t = Fexp	− $

	

, (S6) 

where Fis the instantaneous radiative forcing at the time X is injected into the 

atmosphere, and τ atmospheric lifetime of X. Hence AGWP, or time-integrated radiative 

forcing, over time horizon t for gas X can be derived as the following 

AGWP = @ RF#

t

$



dt = @ Fexp	− $

	



$



dt = Fτ B1 − exp	− $

	

D. (S7) 

The conventionally chosen time horizons for GWP comparisons are 20-, 100-, and 500-

years (IPCC, 1990). The atmospheric lifetimes of the VSLS considered here are all less than 1 

month, i.e. t ≪ τ . Hence, for these VSLS 

AGWP ≅ Fτ. (S8) 

On the other hand, the UIUC RTM calculates the radiative forcing change due to 

sustained emission of a gas. The following deduction shows that the AGWP of X just equals the 

radiative forcing caused by sustained X emissions. 

Considering a sustained emission such that one unit mass X is emitted in one unit time, 

the radiative forcing caused by such sustained emission at time t can be calculated 

RFGt = @ RF#

u − t

$



du = @ Fexp	− $I

	



$



du = Fτ B1 − exp	− $

	

D. (S9) 

If t is sufficiently longer than τ, 

RFG ≅ Fτ. (S10) 

The above derivation (Eqs. 3 and 5) shows that for a VSLS, both the AGWP and 

radiative forcing caused by sustained emission of the strength one unit mass per unit time can be 

approximated to the product of Fand its atmospheric lifetime. 
Table S1. Instantaneous radiative forcing (in W m-2 ppb-1) for each of the six unsaturated 

halogenated hydrocarbons calculated following Pinnock et al. (1995) and calculated in the UIUC 

RTM, both assuming constant mixing ratio profiles for the gases of interest. 

gas IRF Pinnock IRF UIUC RTM

HFO-1234yf 0.22 0.20 

HFO-1234ze(E) 0.27 0.24 

HFO-1234ze(Z) 0.20 0.19 

HFO-1225ye(Z) 0.25 0.23 

HFO-1225ye(E) 0.24 0.23 

tCFP 0.214 0.20