IX. HALOCARBON GLOBAL WARMING POTENTIALS - National Oceanic And .
IX. Relative HALOCARBON GLOBAL POTENTIALS Effects on Global Warming WARMING of Halogenated Methanes Industrial Interest and Ethanes of Social and D. A. Fisher and Charles H. Hales E. I. du Pont de Nemours & Company Wilmington, DE Wie-Chyung Wang, Atmospheric Malcolm K. W. Ko and and Environmental Research, Cambridge, MA " / / N. Dak Inc. EDING PAGE Sze BLAr, K NOT FILMED
GLOBAL WARMING EXECUTIVE Halocarbon of the relative Global Warming environmental Potentials SUMMARY have been defined effects of halocarbons the HGWPs of the hydrohalocarbons to a lesser degree on the molecular and calculated to be made. in order to allow estimates The results presented depend primarily on the atmospheric IR absorption characteristics. lifetime here indicate that of the compounds and The reduction in HGWP that might be expected due to use replacement of a CFC by a hydrohalocarbon can be estimated by taking the ratio of the HGWP of the hydrohalocarbon to the HGWP of the CFC it would replace. For example, .010)/(3.05) 0.085 use application the reduction 0.003. Of course, deled chemistry and dynamics radical reactions to assumed influenced by the changes depending times, once better data is available to be reasonably values of other radiative Calculated time-dependent longer quantities and their direct effect on the chemical with the respective values appear insensitive or increase the relative uses of CFC-12 by HCFC-134a of the compound is (0.26 required in the values reported here agree between models reasonably well once accounting is in lifetimes, uncertainties in the values still exist due to the uncertainties in mo- expect that these values will be updated The HGWP in replacing must also be taken into account. Although the HGWP made for the differences hydroxyl in HGWP in calculated Global robust parameters for the ultraviolet reactions We and the since their calculated values are nearly gases. The minor shifting of the HGWP values in primarily lifetimes their lifetimes Warmings of these compounds. compounds. and therefore the abundance relative global warmings for halocarbons on whether the Relative lifetimes are shorter asymptotically in the atmosphere. are initially on order unity but decrease or longer than that of the reference approach the HGWP gas. At values. 381 PRECEDING PAGE BLA 'K NGT FILMED
N92"15447 RELATIVE METHANES EFFECTS ON GLOBAL AND ETHANES WARMING OF HALOGENATED OF SOCIAL AND INDUSTRIAL INTEREST Donald A. Fisher and Charles H. Hales E.I. du Pont de Nemours Wei-Chyung Wang, Atmospheric Malcolm & Company K. W. Ko and N. Dak Sze and Environmental Research, ING Inc. PAGE BLI'.', K NOT FILMED
GLOBAL WARMING ABSTRACT The relative potential global warming effects for several halocarbons (CFCs -11, 12, 113, 114, and 115; HCFCs 22, 123, 124, 141b, and 142b; and HFCs 125,134a, 143a, and 152a; carbon tetrachloride; and methyl chloroform) have been calculated by two atmospheric modeling groups. These calculations were based on atmospheric chemistry and radiative convective models to determine the chemical profiles and the radiative CFC-11 processes. agree reasonably ences among The resulting relative greenhouse well as long as we account results are discussed. trace gas levels assumed. Sensitivity Transient relative of relative global warming for differences warming warming when normalized between modeled to the effect of lifetimes. values is determined effects Differ- with respect to are analyzed. 1. INTRODUCTION A systematic environmental includes the potential effects for rising environmental evaluation of replacements for fully halogenated chlorofluorocarbons (CFCs) of each replacement chemical on global warming. While the major focus concerns centers on the potential effects of long-lived the role of these gases as contributors to an enhanced greenhouse tion. This concern is based on the ability of these gases to absorb 'window' 8 and 12/am. between First, a brief background The radiative to establish and thermal balance infrared primarily surface and atmosphere ozone, also needs examina- radiation the role of these gases in the 'greenhouse of planet Earth is established and visible) solar energy to the Earth's CFCs on stratospheric or global warming in the atmospheric warming' by balancing phenomena. the incoming with the outgoing (infrared) radiation (UV from the Earth's surface and atmosphere eventually being lost to space. Infrared energy is partially blocked at many wavelengths by naturally occurring gases such as carbon dioxide, methane, and stratospheric water vapor. These gases absorb energy at fundamental contributes frequencies characteristic of their structure. and is eventually re-radiated. tive balance of the infra-red cooling process. Hence, the concern significantly impede infrared cooling of the Earth with a decrease in energy loss to space and a corresponding increase in the Earth's The atmosphere surface 'window' between However, that increasing change the radia- CO2 concentration will temperature. 8 and 12/am is virtually transparent, that absorb energy at these wavelengths, tially unimpeded. Changing gas concentrations This energy to local warming outgoing infrared radiation i.e. since few gases are present passes through both C-CI and C-F bonds have natural vibrational, the atmosphere bending, essen- and rotational excitation frequencies in this infrared frequency range such that CFCs absorb the infrared energy to become very effective greenhouse gases. Their effectiveness as greenhouse gases is accentuated by their long lifetimes. is important Since functional to estimate replacements of these gases is determined gases build up higher tropospheric tiveness gases are the infra-red of energy absorbed there is yet another concentrations. within these intervals Besides the influence infrared energy in the window their potential impact on global climate as part of this evaluation. strated below, the effectiveness as greenhouse may also absorb Longer in determining i.e. the wave length intervals lived the effec- and the amount by each molecule. on the infrared radiative aspect of the radiative importance it As will be demon- in large part by their lifetimes. Of fundamental band strengths, region, fluxes at the top of the atmosphere perturbations from halogenated compounds and at the surface, -- namely the addi- 385 PRECEDING PAGE B' ' '" "-',,,a NOT F:LMED
GLOBALWARMING tional heating to increase induced in the tropical temperatures considerable significance Candidate alternatives HFCs) or carbon, upper troposphere in this region. Any change and lower for the tropospheric-stratospheric are composed hydrogen, and fluorine hydrogen which has the potential near the tropopause exchange of either carbon, chlorine stratosphere in the temperatures water region is of (hydrofluorocarbons or vapor. and fluorine (hydrochlorofluorocarbons or HCFCs). For simplici- ty, both classes of compounds are referred to as hydrohalocarbons. Because they contain hydrogen, the hydrohalocarbons are subject to destruction in the atmosphere through reaction with hydroxyl radicals. This destruction mechanism pounds (see [Fisher of these gases). upper factor et al. (1989a)] By contrast, stratosphere. a primary leads to much shorter for a discussion This paper examines below, their potential the calculated lifetimes of the chemistry the only known destruction As will be shown in reducing atmospheric process the shorter for the hydrohalocarbon affecting the atmospheric of CFCs is through atmospheric lifetime comlifetimes photolysis of HCFCs in the and HFCs is to affect global warming. greenhouse effects of several one and two carbon halocarbons. Esti- mates of these effects will be quantified in terms of a relative potential to enhance global warming (halocarbons global warming sient relative potential or HGWP). warming effects Sensitivity to assumed will be analyzed. Table 1 Compounds HALOCARBON FORMULA IUPAC CFC- levels of trace gases will be examined. Examined in this Study NAME CC13F METHANE, CFC-12 CFC- 113 CC12F2 CCI2FCCIF2 METHANE, DICHLORODIFLUOROETHANE, 1,1,2-TRICHLORO1,2,2-TRIFLUORO- CFC- 114 CCC1F2CC1F2 ETHANE, 1,2-DICHLORO- CFC-115 CCIF2CF3 ETHANE, CHLOROPENTAFLUORO- HCFC-22 CHCIF2 METHANE, HCFC-123 CF3CHC12 HCFC- 124 CF3CHCIF ETHANE, ETHANE, HFC- 125 HFC- 134a CF3CHF2 CF3CH2F ETHANE, 2-CHLORO-1,1,1,2-TETRAFLUOROPENTAFLUORO- ETHANE, 1,1,1,2-TETRAFLUORO- HCFC- 14 lb CC12FCH3 ETHANE, HCFC- 142b CCIFECH3 HFC- 143a CF3CH3 ETHANE, ETHANE, 1,1-DICHLORO-I-FLUORO1-CHLORO- 1,1-DIFLUORO- CHF2CH3 ETHANE, CC14 METHANE, CCI3CH3 ETHANE, HFC- 152a TRICHLOROFLUORO- CHLORODIFLUORO2,2-DICHLORO-1,1, 1,1, I-TRIFLUORO1, I-DIFLUORO- CARBONTETRACHLORIDE METHYL CHLOROFORM 386 1,1,2,2-TETRAFLUORO- TETRACHLOROI,I,I-TRICHLORO- I-TRIFLUORO- Tran-
GLOBAL WARMING Halocarbon Global Warming Potential is based on a concept similar to Ozone Depletion Potential and is used to describe the relative potential of each halocarbon as a greenhouse gas. No attempt is made to calculate HGWPs for non-halocarbon gases such as carbon dioxide and methane. Because of the current atmospheric concentrations and spectral locations of the infrared absorption bands of these other gases, calculated global warming is not a linear function with increases in their atmospheric concentrations. In contrast, a calculated warming is linearly proportional to concentrations of halocarbons. Thus, Greenhouse Warming Potentials Two atmospheric Pont Central Radiative modeling Research Convective groups, (Du Pont), and methane Atmospheric have calculated considered would not be meaningful. and Environmental HGWP values in the literature This paper will discuss the definition of HGWP, Research, for sixteen gases. These as well as examine groups used et al. ozone (Fisher, formula et al., 1989a). the basis for selecting of the differences and Du 1985, Owens 1 along with their chemical for effect on stratospheric by the two models and an examination Inc. (AER), (Wang and Molnar in this study are listed in Table names and are the same as evaluated The results calculated results dioxide models that are described 1985). The halocarbons and IUPAC for carbon its definition. and uncertainties in model is also presented. 2. DEFINITION BASIS Halocarbon Global Warming Potential (HGWP) is defined in a manner parallel to the definition of Ozone Depletion Potential. It is defined as the ratio of calculated warming for each unit mass of a gas emitted into the atmosphere relative to the calculated warming for a mass unit of reference gas CFC- 11. This definition was chosen as a representative measure of the potential of a compound to effect global warming for several reasons: (1) It provides a measure for each unit released of the cumulative into the atmosphere effect on the radiastive (3) It provides a measure effect of CFC-11 The first of these reasons of the maximum over its chemical lifetime (see below). (2) The HGWP yields a single value for each compound calculated balance calculated rather than a time varying multitude effect of a compound compared in that it estimates the cumulative of values. to the maximum on an equal mass basis. is perhaps the most important chronic effect on global warming of each unit released. An illustrative test was performed which quantified the chronic effect from a single pulsed release of test gas into the atmosphere, analogous to a test on effect on stratospheric ozone (Fisher et al., 1989a). The test used the Du Pont model to calculate over a 500 year time period following impulse releases 387 of HCFCs cumulative global warmings -123, -22, and CFC-11.
GLOBALWARMING 0.022 I 0.020 d I t t t r J t I I , SPECIES AREA (deg.*yr) RATIO to CFC-11 HGWP CFC-11 HCFC-22 HCFC-123 1.176 0.358 0.019 1.0 0.30 0.016 1.0 0.29 0.015 0.018 0.016 0.014 dts 0.012 (deg. T I K) 0.010 I 0.008 i 0.006 - 0.004 - 0.002 - I "\" 0.000 ' 0 I I 20 40 I 60 i " -7 . ", 80 100 t t 120 140 I i 160 i 180 200 Year Figure 1. Calculated Change in Surface Temperature kg of Specified Gas The calculated following atmospheric cumulative warmings are shown in Figure the release and tails off with an exponential lifetime of the species. such an event echo the relative a Pulsed Emission having a time constant As seen in the insert table, the time-integrated calculated this is not surprising of 5.0x10" *9 1. For each case, the effect peaks very rapidly decay function values of the HGWP Appendix A of Fisher et al. (1989a), greenhouse warming. Following warming from steady state figures. if the response function, equal to the following Referring to g(t), is to represent 3. DEFINITIONS In order to make the definition of HGWP consistent between of relative effects, the following criteria have been selected: 1) Trace gas levels -- Changing the concentration models as well as a conservative of other trace gases will affect the calculated estimate future equilibrium temperature rise from gases under evaluation here for two reasons. First if there is overlap of absorption spectra, certain bands have less effect. Secondly, chemistry and therefore lifetime can be 388
GLOBALWARMING affected by perturbation of these chemicals. Current levels of CO2, CH4, N20, 03 and stratospheric H:O were used in model calculations. Sensitivity of this assumption will be tested in a following section. 2) Gas perturbation responses levels -- Atmospheric large enough to avoid the "noise concentrations levels" of the test gases were chosen of the numerical to yield model models and still be in a linear response region. 3) Reference gas -- CFC-11 has been chosen as the reference compound er to have a reference material consistent for both HGWP and ODP. 4) Specific Surface Temperature Change -- We define the calculated for HGWP calculations surface a one part per billion surface increase of any gas to be specific surface temperature in ord- temperature increase for change, or symbolical- ly dT s. The HGWP definition resembles Calculated IR forcing Calculated Emission IR forcing Since radiative IR forcing is the net change convective to (moleculear [dTs(CFC can chemically influence a surface change approximately below) and since lifetimes are proportional * emission rate), an equivalent proportional to the ratio of atmospheric form of this definition is: 11)/Molecular the distribution of affecting weight(CFC heating 11)] rates indirectly as well since they of ozone which would affect both the solar and the long wave of model results indicates that this is a second order effect, of these calculations at least two (Wang et al. 1989). CALCULATIONS appropriate input to these radiative chemistry Once the concentration vective temperature below the IR effect and well below the sensitivity communication, The primary using X in IR flux at the tropopause. 11) * Lifetime(CFC rates. An examination orders of magnitude 4. MODEL X/ state) of CFC-11 Note also, many of the gases have the potential private is: due to CFC-11/ models calculate weight definition [dTs(x) * Lifetime(x)/Molecular weight(x)] . HGWP heating Thus for any gas, the general due to Compound rate (steady to the IR forcing level (to be examined abundance definition. Emission rate (steady state) of Compound . HGWP Note: the ODP model. calculations are the altitudinal steady-state concentration profiles models. profile is determined, These models utilize infrared the effect of each gas is calculated absorption 389 spectra to quantify using a Radiative Con- a gas's ability to absorb IR
GLOBAL WARMING Table 2 Total Rogers Varanasi Gehring Chudamani (1988) et al. (1983) (1987) CFC-11 2389 2566 CFC-12 CFC-113 3364 4822 3267 3507 CFC-114 5935 3937 Stephens (1988) & of Halocarbons Kagann Species & Band Strengths Magid (1988) 2389* 3310 3126 3240* 3401" 4141" CFC-115 4678* HCFC-22 2399 2554* HCFC- 123 2552 2859* HCFC- 124 4043* HFC- 125 HFC- 134a 3908* 3169 3272* HCFC-141b 1732 1912" HCFC- 142b 2474 3401" 2577* HFC- 143a HFC- 152a 1648" 1195" CC14 CH3CC13 1184 1209" * Infrared data used in model calculations The IR data from Magid tegrated energy band strengths and thereby accounts were given with spectral impact the earth's that the solar heating culation (1988) resolutions are given here so that they can be compared is balanced heat balance. by the infrared for the amount of energy Equilibrium temperature cooling at all altitudes absorbed of 0.5 to 0.25 cm -1. The in- to other data. profiles are calculated through the atmosphere. by each IR gas (the band strength) such The cal- at specified wavelengths (the band location) including spectral overlap with other IR gases. Quantitative infrared data for this input are available from literature sources for the CFCs (Kagann et al. 1983; Varanasi and Chudamani, 1988; and Rogers and Stephens, from industry laboratories Total band strengths the exception (Magid available 1988) and measurements 1988, and Gehring for these calculations and the HFCs were obtained as shown in Table 2 are within about of Rogers and Stephens (1988). The band strengths used for the model calculations with an asterisk. Since there appear to be systematic measurements, the values from a common the compounds of interest in this study. For compounds (1987) for the HCFCs 1987). differences between data base [Magid (1988)] was used. 390 not available laboratories 10% with are marked for band strength were used since it covered from this source, most of data from Gehring
GLOBALWARMING 0 J 6 6 ., U3 (- J 6 U3 03 "O A Cs e d E O co { e J d 6 I-- Cs e 391
GLOBALWARMING Both these data sets were measured not yet available, assumption band strengths and strengths wave lengths between in this region sorption once temperature and band locations for the absorption the Du Pont radiative-convective occurs at room temperature. Since temperature used in the study were assumed will need to be checked Individual cations band strengths model. of the spectrum. Tables 4 and 5 detail preliminary in these calculations. amount Absorption Some species dependent data sets are through the atmosphere. measurements used in this work broken The greatest 1070 and 1400 cm-'. in the 934 to 1070 cm -t region dependent are important spectra constant become available. Table 3 details the lo- down into the bin structure of absorption for many species by methane and N20 in the background (e.g. CFC-113 and therefore overlaps steps of the calculations This occurs at atmosphere and CFC-114) show significant the IR absorption bands of ozone. for HGWP. of ab- Table 4 shows the net IR radia- tive flux at the tropopause (@ 12 km) for tropospheric concentrations of lppbv as calculated by each model. Note that each of the model's calculations were based on different cloud assumptions (Du Pont used fixed 50% grey (albedo 0.5) cloud cover while AER was based on a non-grey Table 5 shows the resulting values for Specific Surface Temperature Each group's results correlate to each chemical's total band strengths, Table 4 Net IR Radiative (at 12 km and 1 ppbv Species Increases cloud with 48.5% with compensation Flux at the Tropopause tropospheric AER mixing ratio) Du Pont CFC-11 0.175 0. 133 CFC-12 0.248 0. 158 CFC- 113 0.223 0.163 CFC-114 0.258 0.181 CFC-115 0.204 0.164 HCFC-22 HCFC- 123 O. 151 0.140 O. 107 0.092 HCFC- 124 0.153 O. 108 HFC-125 0.189 0.119 HFC-134a 0.135 0.095 HCFC-141b 0.109 0.076 HCFC- 142b HFC-143a 0.144 0.111 O. 101 0.087 HFC- 152a 0.092 0.059 CC14 0.080 0.063 CH3CCI 3 0.038 0.033 [2 x CO2] 4.41 3.87 392 cover). for each of the compounds. made by the
GLOBAL WARMING Table 5 Specific (warming Modeled Surface resulting Warming Temperature from 1 ppbv Normalized Increases of each gas) Warming Lambda # value, ) ( K/ppbv) AER Du Pont ( K/ppbv) AER Du Pont ( K/ppbv/Wm-2) AER Du Pont CFC-11 0.135 0.084 0.088 0.102 0.771 0.632 CFC-12 0.202 0.102 0.131 0.124 0.815 0.647 CFC-113 CFC- 114 0.174 0.208 0.103 0.115 0.113 0.135 0.125 0.139 0.780 0.806 0.632 0.635 CFC-115 0.170 0.107 0.1 I0 0.130 0.833 0.652 HCFC-22 0.124 0.070 0.081 0.084 0.821 0.650 HCFC-123 0.111 0.059 0.071 0.072 0.793 0.644 HCFC- 124 0.126 0.070 0.082 0.084 0.824 0.645 HFC- 125 0.160 0.078 0.104 0.094 0.847 0.654 HFC- 134a 0.114 0.061 0.074 0.074 0.844 0.647 HCFC-141b 0.086 0.048 0.056 0.059 0.789 0.637 HCFC-142b HFC-143a 0.120 0.092 0.066 0.054 0.078 0.060 0.080 0.066 0.833 0.829 0.651 0.625 HFC- 152a 0.076 0.038 0.049 0.046 0.826 0.649 CC14 0.062 0.040 0.040 0.048 0.775 0.628 CH3CCI3 0.027 0.020 0.018 0.025 0.710 0.618 Species # Normalized by : dTs *2 K/(dTs where radiative convective models ences due to chemical tern (Owens et al., One can account by the calculated the two model Also included calculated table, reactivity. for effects results, results. surface warming differences to different of the various by other IR active gases and for profile feedback from a doubling All results are credible temperature of carbon with previously of tropospheric assumptions by normalizing dioxide figures differ- reported pat- feedbacks. the surface and a common of Table 5, indicate to 2 significant warming good agreement warming of 2 C. between at best. of the climate feedback factor, 1, which is the ratio of the model change to the perturbation are consistent are consistent treatments shown in the middle two columns of the two forms One generalization absorption The inter-model on Table 5 are tabulations these values equivalency for overlapping 1985) due primarily surface The normalized for 2X CO2) dT s for 2X CO2 is 3.08 K using AER model 1.651 K using Du Pont model in the net radiative for each of the models thereby of the HGWP validating forcing. As seen from the the assumptions made for definition. at this point is drawn from this set of data. Whereas 393 the total infrared band strengths
GLOBAL WARMING Table6 HalocarbonGlobal WarmingPotentialsBasedon ModeledLifetimes Species HGWP rel. to CFCll AER Du Pont CFC-11 1.0 1.0 CFC-12 3.5 2.9 CFC-113 1.5 1.4 5.4 4.5 CFC-114 CFC-115 13. 8.2 HCFC-22 0.49 0.29 HCFC- 123 HCFC- 124 0.026 0.14 0.015 0.080 HFC- 125 0.84 0.42 HFC- 134a 0.39 0.22 HCFC-141b 0.12 0.073 HCFC- 142b 0.51 0.29 HFC- 143a HFC- 152a 0.97 0.045 0.63 0.024 CC14 0.36 0.36 CH3CC13 0.026 0.022 are on the average comparable among the species, both the net IR flux and the specific surface warming values for HCFCs and HFCs on average are lower than values for CFCs by 40%. This lower value results from the fact that most hydrogenated halocarbons have bands NzO as well as water vapor unlike CFC-I1 and CFC-12. Because the total infrared band strengths for halocarbons that overlap the bands are of the same order of both of magnitude CH 4 and (within a factor of 3x) and generally share the same amount of overlap with other radiatively active gases, the dT s values have a similar range. However, once atmospheric lifetime factors are utilized to calculate HGWP values, the spread among chemicals is much more pronounced. HGWP results with a range among chemicals sensitivity factor is removed Table 6 shows each modeling of about 400X. Between since we are normalizing modeling groups, results to CFC 11, yet substantial sist. Most of these differences are due to differences in modeled lifetimes. As previously er et al. (1989a), calculated lifetimes are only in fair agreement between models. group's the tropospheric differences reported per- in Fish- Since lifetime has a dominant factor on calculated HGWP, basing the HGWP values on a common reference set of lifetimes seems appropriate. Table 7 shows the results of such a rescaling. The reference lifetimes for CFCs are based on the estimates used in model calculations done for the WMO 1989 report. Reference lifetimes for HCFCs and HFCs are from the analysis of Prather (1989). As seen in this table, normaliza394
GLOBAL WARMING Table7 Halocarbon Global Warming Species Potentials Based on a Common Reference* Lifetimes Set of Reference Lifetimes AER DuPont (Yrs) CFC-11 60. 1.0 1.0 CFC-12 120. 3.4 2.8 CFC-113 90. 1.4 1.4 CFC-114 200. 4.1 3.7 CFC-115 400. 7.5 7.6 0.37 0.34 HCFC-22 15.3 HCFC-123 1.6 0.020 0.017 HCFC-124 6.6 0.10 0.092 HFC- 125 28.1 0.65 0.51 HFC-134a HCFC- 141 b 15.5 7.8 0.29 0.097 0.25 0.087 HCFC- 142b 19.1 0.39 0.34 HFC-143a 41.0 0.76 0.72 HFC-152a 1.7 0.033 0.026 0.34 0.35 0.022 0.026 CC14 50. CH3CCI3 6.3 * Lifetimes for CFCs are based on estimated lifetimes Lifetimes for HCFCs and HFCs are based on Prather, tion in this fashion diminishes differences between used in scenario 1989. the two model's development results. Furthermore, in WMO, 1989. the HGWP values for fully halogenated CFCs range from 1.0 to 7.5 whereas the HCFC and HFC values range from 0.02 to 0.7. 5. SENSITIVITY Calculated and N20. TO TRACE HGWP vlaues Because GAS LEVELS have all been based on present the HGWP values are for consideration have examined the sensitivity of these parameters if current trends continue. The trace gas changes HGWP day levels of trace gases of CO2, CH4, CO, and the resulting in future atmospheres calculated changes in lifetimes, values (from the AER model) are shown in Table 8. Calculated for tested CFCs and HCFCs bation. were compared as well as today's, we to changes in CO2 and CH4 to levels that might be achieved to a reference 395 atmosphere surface changes including temperature in surface the assumed rises, and temperature gas pertur-
GLOBALWARMING Table 8 Sensitivity Study Variation in Trace Gase Levels and Impact on HGWP values (AER 1-D model) Species Atmosphere Lifetime (yrs) dT s ( C/ppb) Present CFC-11 HCFC-123 60 125 20 2.1 60 61 126 128 23 20 2.5 2.1 Present 0.14 0.20 0.12 0.11 0.14 0.20 0.12 0.11 0.12 0.17 0.12 0.11 1.0 3.5 0.49 0.026 1.0 1.0 3.5 3.4 0.56 0.49 0.031 0.027 4 Day (1.6 --* 3.2 ppb) CO2 (340 HGWP HCFC-22 CH4 (1.6 3.2 ppb) CO2 (340 680 ppm) CH Day CFC-12 Present 680 ppm) Day CH4 (1.6 3.2 ppb) CO2 (340 680 ppm) As seen in Table 8, trace gas changes have little effect on HGWP on CFC radiative forcing because the albedo feedback the radiative forcing for CFCs -11 and -12 is weakened of the HCFCs, resulting in slightly 6. TIME DEPENDENCE greater OF RELATIVE HGWP values. COz has the greatest effect is weaker in the warmer atmosphere. As a result, somewhat. Methane affects the chemical lifetimes values GLOBAL for these compounds. WARMING Since the HGWP parameter is based on steady state effects, it does not describe the relative time-dependent effects of constituents on warming. Even though the HGWP is an equivalent measure of the cumulative warming during its lifetime is also of interest. The calculated warmings for each unit mass emitted, for a number of halocarbons the transient response to a constant emission level are shown in Figure 2. As seen, the calculated warming reaches an asymptote rapidly for the HCFCs, but requires state for CFCs. These response patterns echo the respective patterns dances for each species, as seen in Figure 3. longer periods to approach for increases in atmospheric steady abun- Relative warmings are shown in Figure 4. For HCFCs, the relative effects are at a maximum at very short times. One can easily show (using L'Hospital's rule), that the initial relative value is the ratio of the value of the Specific corresponding Surface ratio for CFC-11. Temperature Increase Thus the relative dividual effects are small. However, as atmospheric ( C/ppb) / moleculear weight -- relative to the effects are on the order unity at times when the inconcentrations 396 build and chemistry differences affect
GLOBAL WARMING 0.70 0.65 0.60 0.55 0.50 0.45 0.40 dts (deg. 0.35 K) 0.30 0.25 0.20 / CFC-11 J 0.15 0.10 HCFC-141b 0.05 . 1 I HCFC-22 0.00 0 50 100 150 200 Time Figure 2. Change Gas at 5 x10"'8 of Calculated Warming Following kg/yr [Du Pont 1-D Model] 397 250 300 350 400 450 (Yrs) a Step Change of Emission of Specified
GLOBAL WARMING t 1.4e 17 I I t I I I I I 1.3e 17 1.2e 17 1.1e 17 le 17 9e 16 8e 16 F col 7e 16 6e 16 5e 16 4e 16 3e 16 -- 2e 16 HCFC-123 -- HCFC-141b -- HCFC-22 le 16 \ Oe O0 0 50 100 150 200 250 Time 300 350 400 450 500 (Yr) Figure 3. Column of (hydro) Chlorofluorocarbons Following Step Change of Emission of Specified Gas at 5.0 x 10" *8 kg/yr. [Du Pont 1-D Model] 398
GLOBAL 5.0 I I I I t I I WARMING I / f t 4.5 / s / / 4.0 3.5 " (9 ,m 3.0 2.5 CFC-12 2.0 1.5 1.0 0.5 0.0 . 0 F . 50 t . 100 P . 150 - - . 200 Time Figure 4. CalcuLated (CFC-11 Reference) Relative Warming Following [Du Pont 1-D Model] 399 I. 250 I. 300 . 350 ff . 400 450 (Yrs) a Step Change of Emission of Specified Gas
GLOBAL WARMING (Du Pont 0.12 1-D Model) t I t I I I /J 0.11 4.p , ,.z " "" 0.10 J /. f * f 0.09 /" p p / /" ,/ / /'" / 0.08 // /, j J / I ./t / / // // f' 0.07 // /. i"" dTg 0.06 (deg K) /p#' 0.05 p j p ," /" ,/" // 0.04f i" . 0.03 0.02 0.01 0.00 -10 I I I I I I I I I I 0 10 20 30 40 50 60 70 80 90 100 Time (Yrs) with various CFC-11 CFC-12 .HCFC-22 . HCFC-123 . HCFC-141b . CFCl15 No Replacement Figure 5. Transient Calculated species at t 0 and constant Global Warming; emission. 400 Ib/for/Ib replacement of CFC-11
GLOBAL WARMING the relative amount in the atmosphere, the relative effects either grow or decrease depending on whether the lifetimes are longer or shorter than that of CFC-11. As seen in Figure 4, the HCFCs have lifetimes shorter than the lifetime of the reference HGWP value with a time constant gas and have relative equal to the lifetime effects that grow with time asymtotically OWN lifetime. Another perspective transitions approaching warming. Longer their HGWP ing from substitution for CFC-11 lived species of compounds were meant to estimate were used, are substituted of THEIR and the resulting the warming scenarios changes per-
a primary factor in reducing their potential to affect global warming. This paper examines the calculated greenhouse effects of several one and two carbon halocarbons. Esti-mates of these effects will be quantified in terms of a relative potential to enhance global warming (halocarbons global warming potential or HGWP).
controversies. This article discusses amongst cause of global warming and consequences of global warming on the environment. Keywords:Global warming, Greenhouse gas, Global environment, Atmosphere. *Corresponding Author: Ranjana Bhatt, ranjanabhatt83@gmail.com INTRODUCTION Global warming is a very large area of scientific uncertainty.
CHAPTER 13 Ozone Depletion Potentials, Global Warming Potentials, and Future Chlorine/Bromine Loading . pound used may be emitted into the global atmosphere (see Chapter 10).
Humans can't reduce global warming, even if it is happening. Humans could reduce global warming, but people aren't willing to change their behavior so we're not going to. Humans could reduce global warming, but it's unclear at this point whether we will do what's needed. Humans can reduce global warming, and we are going to do so successfully. 12.
glass holder to cool. FEP and PFA Teflon films (2 mil, Livingstone Coating Corp.) were supported by thin halocarbon wax-coated aluminum washers. The Teflon film was pressed onto the warm halocarbon wax coating, which held the film firmly in place. After cutting away the excess
0.5% of span (ASME B40.100 Grade 2A) 0.5% of span (ASME B40.100 Grade 2A) 0.5% of span (ASME B40.100 Grade 2A) 0.5% of span (ASME B40.100 Grade 2A) Dampening Glycerin, Silicone, Halocarbon NA Glycerin, Silicone, Halocarbon , PLUS ! Performance Glycerin, Sili
talks about global warming. They say gasoline cars cause the problem and that the gasoline tax needs to be increased to stop it. Gee, you are so smart, Mol! Greenhouse gases such as CO2 and methane emitted from burning fossil fuels contribute a lot to global warming. Various measures are studied to cut those gases. The introduction of
caused global warming, worry about the threat, and support for several climate policies over the past 14 months. Global Warming Beliefs and Attitudes Most registered voters (74%) think global warming is happening, including 98% of liberal Democrats, 85% of moderate/conservative Democrats and 70% of liberal/moderate Republicans.
tank; 2. Oil composition and API gravity; 3. Tank operating characteristics (e.g., sales flow rates, size of tank); and 4. Ambient temperatures. There are two approaches to estimating the quantity of vapor emissions from crude oil tanks. Both use the gas-oil ratio (GOR) at a given pressure and temperature and are expressed in standard cubic feet per barrel of oil (scf per bbl). This process is .
