Department of Earth System Science

Firn-air and ambient air measurements of CHF₃ (HFC-23) from three excursions to Antarctica between 2001 and 2009 are used to construct a consistent Southern Hemisphere (SH) atmospheric history. The results show atmospheric mixing ratios of HFC-23 continuing to increase through 2008. Mean global emissions derived from this data for 2006–2008 are 13.5 ± 2 Gg/yr (200 ± 30 × 10¹² gCO₂-equivalent/yr, or MtCO₂-eq./yr), ∼50% higher than the 8.7 ± 1 Gg/yr (130 ± 15 MtCO₂-eq./yr) derived for the 1990s. HFC-23 emissions arise primarily from over-fluorination of chloroform during HCFC-22 production. The recent global emission increases are attributed to rapidly increasing HCFC-22 production in developing countries since reported HFC-23 emissions from developed countries decreased over this period. The emissions inferred here for developing countries during 2006–2008 averaged 11 ± 2 Gg/yr HFC-23 (160 ± 30 MtCO₂-eq./yr) and are larger than the ∼6 Gg/yr of HFC-23 destroyed in United Nations Framework Convention on Climate Change Clean Development Mechanism projects during 2007 and 2008.