Abrupt reversal in emissions and atmospheric abundance of HCFC-133a (CF₃CH₂Cl)

Hydrochlorofluorocarbon HCFC-133a (CF₃CH₂Cl) is an anthropogenic compound whose consumption for emissive use is restricted under the Montreal Protocol. A recent study showed rapidly increasing atmospheric abundances and emissions. We report that, following this rise, the atmospheric abundance and emissions have declined sharply in the past three years. We find a Northern Hemisphere HCFC-133a increase from 0.13 ppt (dry-air mole fraction in parts per trillion) in 2000 to 0.50 ppt in 2012-mid-2013 followed by an abrupt drop to ∼0.44 ppt by early 2015. Global emissions derived from these observations peaked at 3.1 kt in 2011, followed by a rapid decline of ∼0.5 kt yr^-2 to reach 1.5 kt yr^-1 in 2014. Sporadic HCFC-133a pollution events are detected in Europe from our high-resolution HCFC-133a records at three European stations, and in Asia from samples collected in Taiwan. European emissions are estimated to be <0.1 kt yr^-1 although emission hot spots were identified in France. Key Points Atmospheric abundances of HCFC-133a and emissions have suddenly reversed in the last three years The sources of HCFC-133a to the atmosphere are likely from the production of HFC-134a In Europe, the emissions of HCFC-133a are less than 0.1 kt/yr while globally about 1.5 kt/yr