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 0.50ppt in 2012-mid-2013 followed by an abrupt drop to similar to 0.44 ppt by early 2015. Global emissions derived from these observations peaked at 3.1kt in 2011, followed by a rapid decline of similar to 0.5 ktyr(-2) to reach 1.5 ktyr(-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