Radiative Effects and Halocarbon Global Warming Potentials of Replacement Compounds for Chlorofluorocarbons

Abstract

Instantaneous radiative forcing was calculated for 5 fluoroalcohols, 21 fluoroethers, and 5 fluoroamines which had been proposed as the replacement compounds for the currently used chlorofluorcarbons (CFCs) in refrigeration. Theatmospheric lifetimes of the compounds were also estimated from highest-occupied molecular orbital (HOMO) energy. Based on the radiative forcing and atmospheric lifetimes, halocarbon global warming potentials (HGWPs) were evaluated for the replacement compounds. Most of the HGWP values were smaller than 0.1 owing to their shorter lifetimes, and the results indicate that these compounds could be valid candidates as replacements for currently used CFCs from the point of view of HGWP.The spectral cooling rate profiles were calculated for the replacement compounds in order to study the vertical structure of their radiative effects. It was found that overlapping of the absorption bands of a compound with those of ozone causes a significant cooling in the stratosphere, even if the compound does not exist in the stratosphere. This cooling does not directly relate to the HGWP value and the cooling rate profile in the troposphere. Therefore, it can be said that the vertical structure of the radiative effects caused by the compounds should be taken into consideration as well as HGWP or GWP values when we assess the environmental effects due to replacement compounds. In this study, one parameter, defined as the ratio of the cooling rate at 30 km and the tropopause, was proposed as a measure of the cooling in the stratosphere.Spectral-resolution dependency of the calculated radiative effects was also studied. The results show that the resolution should be finer than about 50 cm-1 to calculate the radiative forcing and cooling rate precisely.

Evaluation of the atmospheric lifetime and radiative forcing on climate for 1,2,2,2‐tetrafluoroethyl trifluoromethyl ether (CF3OCHFCF3)

“…The modelevaluated atmospheric lifetime is 11.3 years, mainly due to reaction with OH radicals. The model-evaluated instantaneous-clear-sky radiative forcing is 0.38 W m -2 ppbv -1, about 45% lower than previously estimated [Imasu et al, 1995]. However, the model-estimated cloudy-sky adjusted forcing, needed to calculated GWPs, is about 25% lower than the model-estimated instantaneous-clear-sky forcing.…”

“…The purpose of this paper is to evaluate the atmospheric lifetime, radiative forcing, and GWPs of this compound using radiative transfer and chemical-transport models of the global atmosphere. In a previous study [Imasu et al, 1995] the GWPs of HFE-227 were roughly estimated on the basis of laboratory-determined reactivity of five compounds analogous to HFE-227 along with an estimate of the clear-skyinstantaneous radiative forcing. However, as far as we are aware, these properties of HFE-227 have not previously been evaluated with state-of-the-art models of the global atmosphere.…”

“…The purpose of this paper is to evaluate the atmospheric lifetime, radiative forcing, and GWPs of this compound using radiative transfer and chemical-transport models of the global atmosphere. In a previous study [Imasu et al, 1995] with OH radical are directly measured for this study, and then used in the associated modeling studies.…”

Global warming potentials and radiative efficiencies of halocarbons and related compounds: A comprehensive review

“…Radiative efficiencies for HCFC‐141b reported in the published literature are in the range of 0.12–0.18 W m −2 ppb −1 (mean: 0.15 W m −2 ppb −1 ) [ Fisher et al ., ; Imasu et al ., ; Jain et al ., ; Naik et al ., ; Orkin et al ., ; Pinnock et al ., ; Sihra et al ., ], and the value of 0.14 W m −2 ppb −1 from Fisher et al . [] has been used by AR4 (scaled to the previously recommended CFC‐11 RE of 0.25 W m −2 ppb −1 ).…”

Computational Study on OH and Cl Initiated Oxidation of 2,2,2-Trifluoroethyl Trifluoroacetate (CF3C(O)OCH2CF3)

“…5 However, the presence of C-F bond in HFEs may enhance the strong absorption in the range 1000-3000 cm −1 that may cause a potential greenhouse effect. 6,7 HFEs have ether (─O─) linkage as a result of which they are highly reactive in the upper atmospheric region. It is a known fact that the atmospheric oxidation of HFEs leads to the formation of fluorinated esters as primary products.…”