Correction to “OH reaction rate constant, IR absorption spectrum, ozone depletion potentials and global warming potentials of 2-bromo-3,3,3-trifluoropropene”



This article corrects:

  1. OH reaction rate constant, IR absorption spectrum, ozone depletion potentials and global warming potentials of 2-bromo-3,3,3-trifluoropropene Volume 116, Issue D24, Article first published online: 27 December 2011

[1] Subsequent to the publication of “OH reaction rate constant, IR absorption spectrum, ozone depletion potentials and global warming potentials of 2-bromo-3,3,3-trifluoropropene” by K. O. Patten et al. (Journal of Geophysical Research, 116, D24307, doi:10.1029/2011JD016518, 2011), more recent analyses have shown that an error existed in the calculation of 2-bromo-3,3,3-trifluoropropene (BTP) global warming potentials (GWPs) within that article, which started at paragraph 35 of section 4.5 in the article. During the calculation for GWPs based on WACCM and the UIUC RTM,equation (4) was used with radiative forcing per unit BTP flux rather than unit BTP burden, which resulted in reported GWPs that were low by a factor of the BTP lifetime in years: a factor of 52 for BTP emissions from 30 to 60°N and of 85 for emissions from 60°S to 60°N. This writing is intended to correct this miscalculation and to provide corrected BTP GWPs.

[2] The text in section 4.5 paragraphs 35 to 37 of Patten et al. [2011] should be replaced with the three following paragraphs:

[3] The GWP is calculated as the ratio of tropopause RF integrated over time to a time horizon tH (also known as absolute GWP or AGWP) resulting from a pulse release of a compound to that from a pulse release of the same mass of CO2. We assume that BTP would be removed with a single-exponential decay at its atmospheric lifetimeτ if its emissions stopped, so that the AGWP for BTP is given by

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where the radiative forcing per kg of BTP F0 is obtained by dividing the tropopause RF perturbation by the BTP burden in kg derived from WACCM outputs. tHfrequently is specified as 20, 100, or 500 years for long-lived gases. The lifetime of BTP in the 30°N to 60°N emissions scenario is 7.0 days and that in the 60°S to 60°N emissions scenario is 4.3 days (Table 3), so that the exponential term inequation (4) is effectively zero for tH = 20 years or longer. Thus, the AGWPs for BTP at 20, 100, or 500 years are equal to radiative forcing per kg BTP times lifetime:

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[4] The IPCC 2006 report [Forster et al., 2007, section 2.10.2] supplies AGWPs for CO2 at tH=20, 100, and 500 years:

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[5] Dividing these into the BTP AGWP provides the GWP values shown on the upper lines in the revised Table 6. These low GWPs suggest that the climate effect of BTP will be less than that of an equivalent mass of CO2.

Table 6. Global Warming Potentials (GWPs) for 2-Bromo-3,3,3-Trifluoropropene (BTP) for Time Horizons tH of 20, 100, and 500 Years Derived From WACCM and the UIUC RTMa
Emissions ScenariotH = 20 yrtH = 100 yrtH = 500 yr
  • a

    BTP GWPs based on a tropospherically well-mixed approximation are also shown for comparison.

30°N to 60°N0.910.260.078
60°S to 60°N0.820.230.071
Well-mixed estimate2.10.590.18

[6] We are unaware of other reports of GWP for BTP, but the GWPs reported in this study are lower than GWPs reported for many other short-lived halocarbons. Such GWPs are usually based on a well-mixed approximation in which the halocarbon is assumed to be thoroughly mixed in the troposphere. As noted in the revisedTable 6, the GWP calculated explicitly here are smaller than those calculated using the well-mixed approximation by a factor of 2–3. The well-mixed BTP GWPs are based on a radiative efficiency of 0.193 W m−2 ppb−1 obtained from the IR cross sections in this report by the method of Pinnock et al. [1995]and a well-mixed approximation atmospheric lifetime of 3.0 days estimated by scaling the OH lifetime of methyl chloroform [Prinn et al., 2001; Spivakovsky et al., 2000] by the ratio of OH rate constants at an average tropospheric temperature of 270 K. These well-mixed approximation GWPs are over twice as large as our model-derived GWPs. Many GWPs previously reported for short-lived compounds are upper limits based on the well-mixed approximation, and it should be noted that model-based profiles for very short-lived compounds could result in smaller GWPs than have been previously reported.

[7] Also, sentence 7 of the Abstract (paragraph 1) should be revised to:

[8] The global, annual average atmospheric lifetime of BTP in the former scenario was 7.0 days, its ODP was 0.0028, and its GWP (100-yr time horizon) was 0.26; in the latter scenario, the global, annual average BTP lifetime was 4.3 days, ODP was 0.0052, and 100-yr GWP was 0.23.

[9] Finally, the second-to-last sentence in the Conclusions (paragraph 38) should be revised for the corrected GWP values to:

[10] The direct Global Warming Potential (GWP) of BTP at a 100-year time horizon is estimated as 0.26 for the 30°N to 60°N emissions scenario and 0.23 for the 60°S to 60°N emissions scenario.