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- Title
Global and regional emissions estimates of 1,1-difluoroethane (HFC-152a, CH<sub>3</sub>CHF<sub>2</sub>) from in situ and air archive observations.
- Authors
Simmonds, P. G.; Rigby, M.; Manning, A. J.; Lunt, M. F.; O'Doherty, S.; Young, D.; McCulloch, A.; Fraser, P. J.; Henne, S.; Vollmer, M. K.; Reimann, S.; Wenger, A.; Mühle, J.; Harth, C. M.; Salameh, P. K.; Arnold, T.; Weiss, R. F.; Krummel, P. B.; Steele, L. P.; Dunse, B. L.
- Abstract
High frequency, ground-based, in situ measurements from eleven globally-distributed sites covering 1994-2014, combined with measurements of archived air samples dating from 1978 onward and atmospheric transport models, have been used to estimate the growth of 1,1-difluoroethane (HFC-152a, CH3CHF2) mole fractions in the atmosphere and the global emissions required to derive the observed growth. HFC-152a is a significant greenhouse gas but since it does not contain chlorine or bromine, HFC-152a makes no direct contribution to the destruction of stratospheric ozone and is therefore used as a substitute for the ozone depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). HFC-152a has exhibited substantial atmospheric growth since the first measurements reaching a maximum annualised global growth rate of 0.81 ± 0.05 ppt yr-1 in 2006, implying a substantial increase in emissions up to 2006. However, since 2007, the annualised rate of growth has slowed to 0.38 ± 0.04 ppt yr-1 in 2010 with a further decline to an average rate of change in 2013-2014 of -0.06 ± 0.05 ppt yr-1. The average Northern Hemisphere (NH) mixing ratio in 1994 was 1.2 ppt rising to a mixing ratio of 10.2 ppt in December 2014. Average annual mixing ratios in the Southern Hemisphere (SH) in 1994 and 2014 were 0.34 and 4.4 ppt, respectively. We estimate global emissions of HFC-152a have risen from 7.3 ± 5.6 Ggyr-1 in 1994 to a maximum of 54.4 ± 17.1 Ggyr-1 in 2011, declining to 52.5 ± 20.1 Ggyr-1 in 2014 or 7.2 ± 2.8 Tg-CO2 eqyr-1. Analysis of mixing ratio enhancements above regional background atmospheric levels suggests substantial emissions from North America, Asia and Europe. Global HFC emissions (so called "bottom up" emissions) reported by the United Nations Framework Convention on Climate Change (UNFCCC) are based on cumulative national emission data reported to the UNFCCC, which in turn are based on national consumption data. There appears to be a significant underestimate of "bottom-up" global emissions of HFC-152a, possibly arising from largely underestimated USA emissions and undeclared Asian emissions.
- Subjects
EMISSIONS (Air pollution); ORGANOFLUORINE compounds; CARBYNES; AIR sampling; MOLE fraction; ATMOSPHERE
- Publication
Atmospheric Chemistry & Physics Discussions, 2015, Vol 15, Issue 16, p21335
- ISSN
1680-7367
- Publication type
Article
- DOI
10.5194/acpd-15-21335-2015