Abstract
CFC-113a (CF3CCl3), CFC-112 (CFCl2CFCl2) and HCFC-133a (CF3CH2Cl) are three newly detected molecules in the atmosphere that are almost certainly emitted as a result of human activity. It is important to characterise the possible contribution of these gases to radiative forcing of climate change and also to provide information on the CO2-equivalence of their emissions. We report new laboratory measurements of absorption cross-sections of these three compounds at a resolution of 0.01 cm−1 for two temperatures 250 K and 295 K in the spectral range of 600–1730 cm−1. These spectra are then used to calculate the radiative efficiencies and global warming potentials (GWP). The radiative efficiencies are found to be between 0.15 and 0.3 W∙m−2∙ppbv−1. The GWP for a 100 year time horizon, relative to carbon dioxide, ranges from 340 for the relatively short-lived HCFC-133a to 3840 for the longer-lived CFC-112. At current (2012) concentrations, these gases make a trivial contribution to total radiative forcing; however, the concentrations of CFC-113a and HCFC-133a are continuing to increase. The 2012 CO2-equivalent emissions, using the GWP (100), are estimated to be about 4% of the current global CO2-equivalent emissions of HFC-134a.
Highlights
The emission of halogenated compounds from human activity can cause stratospheric ozone depletion and climate change
It is necessary to provide values for metrics such as the Global Warming Potential (GWP) which is used within the Kyoto Protocol to the United Nations Framework Convention on Climate Change for placing emissions of different greenhouse gases on a CO2-equivalent scale
This paper reports new laboratory measurements of the infrared absorption cross-sections of three of these four compounds (Sections 2–4), and presents for the first time calculations of radiative efficiencies (Section 5) and global warming potentials (GWP) (Section 6) using these cross-sections together with atmospheric lifetimes recently reported by Laube et al [1]
Summary
The emission of halogenated compounds from human activity can cause stratospheric ozone depletion and climate change. CFC-112 concentrations peaked in 1997, and have been falling slowly since ; CFC-112a concentrations (measured since 1999) are believed to have behaved in a similar way These compounds continue to be emitted as a result of human activity At existing concentrations these particular CFCs and HCFCs contribute insignificantly to radiative forcing of climate change, it is necessary to quantify this contribution, for those whose concentrations are increasing, and may become significant in the future. It is necessary to provide values for metrics such as the Global Warming Potential (GWP) which is used within the Kyoto Protocol to the United Nations Framework Convention on Climate Change for placing emissions of different greenhouse gases on a CO2-equivalent scale. This paper reports new laboratory measurements of the infrared absorption cross-sections of three of these four compounds (Sections 2–4), and presents for the first time calculations of radiative efficiencies (Section 5) and GWPs (Section 6) using these cross-sections together with atmospheric lifetimes recently reported by Laube et al [1]
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