Abstract
Abstract. Fluorinated compounds such as NF3 and C2F5Cl (CFC-115) are characterised by very large global warming potentials (GWPs), which result from extremely long atmospheric lifetimes and strong infrared absorptions in the atmospheric window. In this study we have experimentally determined the infrared absorption cross sections of NF3 and CFC-115, calculated the radiative forcing and efficiency using two radiative transfer models and identified the effect of clouds and stratospheric adjustment. The infrared cross sections are within 10 % of previous measurements for CFC-115 but are found to be somewhat larger than previous estimates for NF3, leading to a radiative efficiency for NF3 that is 25 % larger than that quoted in the Intergovernmental Panel on Climate Change Fifth Assessment Report. A whole atmosphere chemistry–climate model was used to determine the atmospheric lifetimes of NF3 and CFC-115 to be (509 ± 21) years and (492 ± 22) years, respectively. The GWPs for NF3 are estimated to be 15 600, 19 700 and 19 700 over 20, 100 and 500 years, respectively. Similarly, the GWPs for CFC-115 are 6030, 7570 and 7480 over 20, 100 and 500 years, respectively.
Highlights
Fluorinated compounds such as NF3 and CFC-115 are potentially important for global warming (Myhre et al, 1998)
In this study we have presented updated values for the IR absorption cross sections and atmospheric lifetimes of NF3 and CFC-115, as well as radiative forcing and radiative efficiencies, taking into account stratospheric adjustment and cloudy skies
The IR cross sections measured in the present study are larger than previously reported for NF3
Summary
Fluorinated compounds such as NF3 and CFC-115 are potentially important for global warming (Myhre et al, 1998). NF3 is being used increasingly as a replacement for banned perfluorocarbons (PFCs) which were utilised in processes such as chemical cleaning and circuit etching. It is an extremely potent greenhouse gas with an estimated 100-year global warming potential (GWP) between 10 800 and 17 000 (Arnold et al, 2013; Robson et al, 2006; Weiss et al, 2008). Weiss et al (2008) reported a 2008 mean global tropospheric mixing ratio of 0.45 ppt increasing at a rate of 0.053 ppt yr−1. The present-day mixing ratio will be close to 1 ppt, assuming no change in emission rate. The present-day mixing ratio will be close to 1 ppt, assuming no change in emission rate. Arnold et al (2013) found undetectable levels of NF3 prior to 1975 in archived air samples and ice cores, indicating that the major source of the gas is anthropogenic
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