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

We report the first multiyear atmospheric record of HCFC-31 (CH₂ClF), 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 (CH₂F₂). 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. Key Point First observations of HCFC-31 in the atmosphere