2018 SCIENTIFIC ASSESSMENT OF OZONE DEPLETION UPDATE ON GWPs AND ATMOSPHERIC LIFETIMES FOR HFCS AND HFOS

The F-Gas Regulation 517/2014 references GWPs based on the Fourth Assessment Report (AR4) adopted by the Intergovernmental Panel on Climate Change, unless otherwise indicated in Annex I. Use and placing on the market bans reference these GWPs. The 2018 Scientific Assessment of Ozone Depletion provides the most up to date GWPs and lifetimes based on improvements in the understanding of reaction rates in the atmosphere and new experimental data. It is worth emphasising that AR4 values continue to apply for the F-Gas Regulation. The AR4 values had been previously revised in the Fifth Assessment Report (AR5 values), and these are also available on the EFCTC website.

The table shows AR4 and 2018 SAP GWPs and 2018 SAP atmospheric lifetimes for some HFCs and HFOs. The data and information available on the EFCTC website will be updated to include this most recent information.

GWP values have been refined over the past three decades with the development of atmospheric science. As GWPs of refrigerant are relative to CO2, any change in the calculated global warming impact (radiative forcing) of CO2 directly affects the refrigerant GWP. In addition, GWPs also depend on the atmospheric lifetime and infra-red absorption spectra (radiative efficiencies) of the refrigerants. Atmospheric lifetime is linked to the reaction rates for the various processes that convert the refrigerant into very low GWP breakdown products and improved knowledge about atmospheric science and radiative efficiencies for HFCs and HFOs has led to revisions in their GWPs.

2018 SAP: HFCs and HFOs are removed from the atmosphere mainly by their reactions with hydroxyl radicals (OH) in the troposphere. The residence times of HFCs in the atmosphere determined by reaction with tropospheric OH and are derived from the corresponding lifetime of methyl chloroform, H3CCl3. Compounds with atmospheric lifetimes shorter than ~0.5 years have been designated as very short-lived substances (VSLSs) as in previous Assessments. The lifetime of VSLSs released into the atmosphere depends on local atmospheric conditions at the emission location. It should be noted that the local lifetimes of VSLSs, which includes the HFOs, are ~10–20% longer than in previous Assessments primarily because they have now been calculated with the same approach that is used for longer-lived HFCs, thereby avoiding arbitrary differences arising from the use of two different approaches. OH reactivity for several compounds has been revised since the last Assessment based on new experimental data and/or analyses. However, these revisions do not substantially change the recommended atmospheric lifetimes. The lifetimes of the HFO (E)-CF3CH=CHCF3 is a factor of ~6 longer because experimental data on the OH reactivity of (E)-CF3CH=CHCF3 became available for the first time since the last Assessment.

See the 2018 Scientific Assessment of Ozone Depletion Chapters 2 (HFCs),Table 2.2 and Appendix A, for the complete information.