The changing ambient mixing ratios of long-lived halocarbons under Montreal Protocol in China

The varying trend of long-lived halocarbons demands close attention of their atmospheric climate impact. Chlorofluorocarbons (CFCs) were phased out in 2008 under the Montreal Protocol in China, and nowadays, hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) are the main substitutes. Since 2000, studies on CFCs, HCFCs, and HFCs, with respect to their ambient mixing ratios and emissions, were intensively performed over China. CFCs declined evidently, while HCFCs and HFCs greatly increased in China due to the successful phase-out of CFCs under the Montreal Protocol. In the Pearl River Delta (PRD) region, the most developed region in China, the increasing and decreasing rates of CFC-11, CFC-12, HCFC-22, and HCFC-141b since 2000 were −3.6 ± 0.5 pptv/yr, −11.7 ± 3.3 pptv/yr, 17.9 ± 4.9 pptv/yr and 7.2 ± 2.0 pptv/yr, respectively. The increase of HCFC-141b in northern China was 1.1 ± 0.6 pptv/yr, much lower than the PRD region. The overall increase of HFC-134a in China was 5.6 ± 0.2 pptv/yr. These rates were significantly higher than those for their corresponding background averages in the northern hemisphere. Other HFCs excluding HFC-134a were of great global warming potentials, but their ambient mixing ratios were reportedly limited in China. The emission ratios between HCFC-22 and CFC-12, and HFC-134a and HCFC-22 were used as the measurements, showing virtual replacement occurring in China. The rapidly increasing contribution of HFCs to climate risk in China requires further observation.