First observations, trends, and emissions of HCFC‐31 (CH₂ClF) in the global atmosphere

We report the first multiyear atmospheric record of HCFC‐31 (CH 2 ClF), based on flask samples and in situ analyses of air from both hemispheres. Although HCFC‐31 has never been produced in large amounts, observed mole fractions in the Northern Hemisphere increased from 2000 onward, reaching 170 ppq (parts per quadrillion, 10 −15 ) in 2011–2012 before decreasing rapidly. By combining our observations with a two‐dimensional atmospheric chemistry‐transport model, we infer an increase in global emissions from 240 t yr −1 in 2000 to 840 t yr −1 in 2011–2012, followed by a relatively fast decline to 570 t yr −1 in 2014. Emissions of HCFC‐31 originate most probably from intermediate product release during the manufacturing process of HFC‐32 (CH 2 F 2 ). The rapid decline in recent years could be due to changes in production methods rather than declines in diffusive sources such as landfills or HCFC‐31 contaminations in merchandised HFC‐32.