Report of the Scientific Assessment Panel OEWG, 33 rd meeting, Bangkok, 24–28 June 2013 ODP and GWP of 1,2-dichlorohexafluoro-cyclobutane (c-C 4 F 6 Cl 2, RC-316c)  lifetime primarily determined by photolysis in the stratosphere  Isomers have different atmospheric photolysis rates and, hence, different atmospheric lifetimes, ODP, and GWP  Both isomers are long-lived; have high ODP and GWP  Commercial R-316c is as a mixture of 52% (E)- and 48% (Z)- isomers Cl (Z)-R-316c(E)-R-316c OEWG Bangkok June 2013 R316c1

UV absorption cross sections of RC- 316c (E)-R-316c Cl (Z)-R-316c Cl Temperature (K) Atmos  Range o Absorption cross sections of the individual isomers have been measured. o Absorption cross sections were measured as a function of temperature o The E-isomer absorbs UV more than the Z-isomer Burkholder et al., 2013 (recent work) OEWG Bangkok June 2013 R316c2

Infrared cross section of RC-316c (E)-R-316c Cl (Z)-R-316c Cl Calculated Radiative Efficiency(W m -2 ppb - 1 ) Burkholder et al., 2013 (recent work) o Measured IR cross sections are slightly different o Calculated radiative efficiency differ by ~10% OEWG Bangkok June 2013 R316c3

Cl (Z)-R-316c (E)-R-316c Atmospheric Lifetime (2-D model) Fleming et al., 2013 ODP (semi-empirical) GWP years 114 years ~0.5 ~ GWP ODP and GWP of RC-316c OEWG Bangkok June 2013 R316c4 Bottom Line: ODP and GWP of R-316c is similar to, and slightly smaller than, CFC-11 and CFC-12