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Chlorofluorocarbons (CFCs)

   Chlorofluorocarbons (CFCs) , which are compounds of carbon, fluorine and chlorine, are artificial substances with greenhouse effects and ozone-depleting potential. CFC emissions are regulated under the Montreal Protocol on Substances that Deplete the Ozone Layer and its Amendments and Adjustments.

JMA Observation

   The figure below shows a time-series representation of CFC-11, CFC-12 and CFC-113 mole fractions observed at JMA's Ryori station. The values exhibit weak short-term variations with no seasonal variability. The mole fraction of CFC-11 peaked at about 270 ppt in 1993 - 1994, and has decreased since then. The value for CFC-12 increased until 1995 and rose gradually thereafter, peaking in 2005. The mole fraction of CFC-113 shows little change in the 1990s and a slight decrease in recent years.

Time-series representation of CFC mole fractions recorded at JMA's Ryori observatory

Provisional values are inclueded.

Mole fraction data of CFCs and other halogenated species collected from worldwide observatories

   Observation data collected from all over the world by WDCGG show that mole fractions of CFCs increased due to industrial production before the Montreal Protocol, then stopped increasing and started to decrease due to industrial regulation based on the Protocol.

   The mole fraction of CFC-11 peaked around 1992 and then started decreasing. The mole fraction of CFC-12 increased until around 2003 and then started decreasing gradually. The mole fraction of CFC-113 stopped increasing in the 1990s, followed by a slight decrease over about twenty years.

   The mole fraction of Halon-1211 has decreased since 2005, and the growth of Halon-1301 mole fractions has levelled off for the last several years.

   The mole fractions of HCFCs (HCFC-22, HCFC-141b, HCFC-142b), used mainly as substitutes for CFCs, have increased significantly during the last two decades. However, the growth of the mole fractions has levelled off for the last several years.

   The mole fraction of CCl4 was maximal around 1991 and has since decreased slowly. The mole fraction of CH3CCl3 peaked around 1992 and decreased thereafter.

   The mole fractions of HFC-134a and SF6 are increasing, but that of HFC-152a has levelled off for the last several years. The mole fraction of CH3Cl does not show significant long-term tendency although clear seasonal cycle can be seen in the dataset.

Time-series representation of halogenated species mole fractions as derived from worldwide observatory data

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